Instruments for Assessing Spirituality in Patients with Chronic or Advanced Illnesses: A Systematic Review of the Last 15 Years.

This systematic review was conducted following the guidelines of the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) 2020 statement. The review protocol was not registered in PROSPERO or any other database prior to conducting the study. However, the methodology was defined in advance, including clear inclusion and exclusion criteria, search strategies, and data extraction procedures, all of which were maintained without changes throughout the entire review process. Searches were conducted in PubMed, Scopus, and Web of Science from January 2011 to December 2024. No language restrictions were applied. The last search was performed on 15 December 2024. The search strategy was developed by the main author and reviewed by the research team. The complete search strings are provided in Table 2 . Studies were included when they assessed the validation and psychometric properties of spirituality scales or instruments used in healthcare. Mixed psychosocial instruments were also included when they contained a specific spiritual dimension that aligned with the operational definition of “current spiritual state.” These instruments do not assess spirituality as a whole but provide validated items that capture aspects of spiritual experience relevant to clinical assessment. Their inclusion allows identifying instruments already used in clinical practice that incorporate spiritual components within broader psychosocial evaluations, ensuring that the review reflects all validated tools capable of assessing the patient’s current spiritual state. The following articles were excluded: Studies in which the instrument was applied to healthy individuals, adolescents, children, healthcare professionals or family members/caregivers. These population groups were excluded from the target population because their spiritual experiences differ substantially from those of patients with chronic or terminal illnesses. Although caregivers may also go through complex spiritual processes in the context of caregiving and illness, scientific literature shows that their spiritual needs, approaches, and meanings are not equivalent to or comparable with those of patients directly affected by illness [ 16 , 17 ]. Scales that assessed only religious aspects without considering the spiritual dimension. Articles published outside the established date range (2011–2024). This timeframe was selected, aiming to complement the previous systematic review published by Monod [ 13 ]. Therefore, the present review presents an updated panorama of the current validated studies. Studies including patients not diagnosed with a chronic or terminal illness, according to the definition of chronic disease established by the World Health Organization (WHO) and the definition of terminal illness by the Spanish Society of Palliative Care (SECPAL). According to the WHO, chronic diseases, also known as noncommunicable diseases, are long-duration conditions with slow progression, resulting from a combination of genetic, physiological, environmental, and behavioral factors, and include cardiovascular diseases, cancer, chronic respiratory diseases, diabetes, among others [ 18 ]. SECPAL, on the other hand, defines terminal illness as an advanced, progressive, and incurable condition, with no reasonable expectation of response to specific treatment, presenting multiple intense, multifactorial, and variable physical problems, with a significant emotional impact on the patient, family, and therapeutic team, and a life expectancy of less than six months [ 19 ]. Measurement instruments consisting of only one item. Patients diagnosed with mental illness or significant cognitive impairment. This exclusion is based on the fact that evaluating the spiritual dimension requires adequate insight, understood as the capacity for awareness and understanding of one’s own spiritual experience. In individuals with psychiatric disorders or cognitive decline, this capacity may be compromised, which affects the validity and reliability of the instruments used to measure spirituality [ 20 , 21 ]. Given these considerations, specific adaptations are necessary for use in these populations [ 22 ]. Therefore, their inclusion could bias the results and compromise the methodological rigor of the study. Studies that did not correspond to a scale validation. Studies in which the instrument was applied to healthy individuals, adolescents, children, healthcare professionals or family members/caregivers. These population groups were excluded from the target population because their spiritual experiences differ substantially from those of patients with chronic or terminal illnesses. Although caregivers may also go through complex spiritual processes in the context of caregiving and illness, scientific literature shows that their spiritual needs, approaches, and meanings are not equivalent to or comparable with those of patients directly affected by illness [ 16 , 17 ]. Scales that assessed only religious aspects without considering the spiritual dimension. Articles published outside the established date range (2011–2024). This timeframe was selected, aiming to complement the previous systematic review published by Monod [ 13 ]. Therefore, the present review presents an updated panorama of the current validated studies. Studies including patients not diagnosed with a chronic or terminal illness, according to the definition of chronic disease established by the World Health Organization (WHO) and the definition of terminal illness by the Spanish Society of Palliative Care (SECPAL). According to the WHO, chronic diseases, also known as noncommunicable diseases, are long-duration conditions with slow progression, resulting from a combination of genetic, physiological, environmental, and behavioral factors, and include cardiovascular diseases, cancer, chronic respiratory diseases, diabetes, among others [ 18 ]. SECPAL, on the other hand, defines terminal illness as an advanced, progressive, and incurable condition, with no reasonable expectation of response to specific treatment, presenting multiple intense, multifactorial, and variable physical problems, with a significant emotional impact on the patient, family, and therapeutic team, and a life expectancy of less than six months [ 19 ]. Measurement instruments consisting of only one item. Patients diagnosed with mental illness or significant cognitive impairment. This exclusion is based on the fact that evaluating the spiritual dimension requires adequate insight, understood as the capacity for awareness and understanding of one’s own spiritual experience. In individuals with psychiatric disorders or cognitive decline, this capacity may be compromised, which affects the validity and reliability of the instruments used to measure spirituality [ 20 , 21 ]. Given these considerations, specific adaptations are necessary for use in these populations [ 22 ]. Therefore, their inclusion could bias the results and compromise the methodological rigor of the study. Studies that did not correspond to a scale validation. The selected articles were then subjected to a full-text review to examine the spirituality measurement instruments in depth. In this phase, scales were excluded if: (1) they referred exclusively to elements of religiosity; (2) they only consisted of one item related to spirituality; (3) there was no evidence that the instrument had been used with clinical outcomes; (4) data on the instrument’s psychometric properties were unavailable; and (5) they were studies other than a scale validation. Finally, scholars and researchers in the field of religion and spirituality were asked to identify any additional scales or questionnaires that met the inclusion and exclusion criteria established in the study. Two reviewers independently screened titles and abstracts obtained from the searches. Full-text articles were assessed for eligibility according to predefined inclusion and exclusion criteria. Discrepancies were resolved through discussion until consensus was reached. Two reviewers independently extracted data using a structured data extraction sheet. Extracted variables included: study characteristics, population, country, instrument type, number of items, dimensions, psychometric results (reliability, validity), and classification of items (cognitive, affective, behavioral). Any disagreements were resolved by consensus. For each instrument, the underlying dimensions of the spirituality construct were established, in addition to the objectives established for the instrument’s development. Data related to the psychometric properties were systematically recorded. When information on correlations with other instruments was available, this was extracted to assess criterion-related validity. Data on concurrent validity were also analyzed when available. Furthermore, studies in which spirituality measurement tools showed correlations in cross-sectional studies or were predictive in longitudinal research on health outcomes were included to analyze both concurrent and predictive validity. Each instrument was evaluated using a scoring system specifically developed for this review and based on recognized standards for instrument development [ 5 ]. This system assesses six methodological domains: content validity, construct validity, criterion validity, internal consistency, test–retest reliability, and sample adequacy [ 23 ]. Each domain is rated dichotomously (0 = absent/insufficient/not reported; 1 = adequately described and methodologically acceptable), yielding a total score from 0 to 6. Higher scores indicate greater methodological rigor and stronger psychometric evidence. The operational definitions and scoring rules for each domain are detailed in Table 3 . The results of this assessment for each included study are presented in the Section 3 . The methodological quality of the validation studies was assessed using a standardized approach based on well-established criteria for psychometric research. Because of the nature of these instrument validation studies, we examined several key areas in each one: (1) how clearly the study objectives and the instrument’s purpose were described; (2) whether the sample size was appropriate for psychometric analyses. In this review, no specific quantitative threshold was applied to determine whether the sample size used in each validation study was “adequate”, given the heterogeneity of the psychometric designs included. However, as a general indicator of sufficiency, we considered whether the authors provided an explicit methodological justification for the sample size or whether the sample size was consistent with widely accepted standards for factor analysis (e.g., approximately 5–10 participants per item, or ≥150 participants for exploratory or confirmatory factor analyses). This criterion was used solely to contextualize methodological quality and was not applied as an exclusion criterion; (3) whether the statistical methods used were suitable for validation, and (4) how thoroughly the psychometric properties were reported. Two reviewers independently assessed the quality of each study. Any disagreements were resolved through discussion or, when necessary, consultation. The results of the quality assessment informed the interpretation of the findings but were not used as exclusion criteria, since the main goal was to provide a comprehensive overview of the available instruments. Studies with methodological limitations are noted in the Section 3 and Section 4 . The development of the included instruments involved defining (a) the conceptual aspect of spirituality that the instrument seeks to assess and (b) the elements that operationalize the concept of spirituality in question. The term “development of the instruments included” does not refer to the authors of this review creating or modifying any scale. Rather, it refers to the development processes described in the original validation studies. This includes how the construct was defined, how the items were generated, the preliminary design of the instrument, and the initial validation steps reported by the original authors. This information was extracted exclusively to evaluate the psychometric quality of the existing instruments. In this study, a classification of measurement tools is proposed that follows the line of reasoning used in instrument development, as shown in Table 4 . Based on the multidimensional framework described in the Introduction, instruments were categorized according to whether they assessed the current spiritual state through affective (A), behavioral (B), and cognitive (C) expressions. Two reviewers independently classified each instrument, and discrepancies were resolved by consensus. The complete classification indicating the presence of each functional dimension is presented in Table 5 and Table 6 . The initial agreement for the classification was excellent (Cohen’s Kappa 0.969). Divergences between the reviewers were discussed and resolved by consensus [ 28 ]. Table of instruments assessing spirituality. A = Affective dimension; B = Behavioral dimension; C = Cognitive dimension. Scores range from 0 to 6, with higher scores indicating a more comprehensive validation process. “No” indicates that the instrument is not contaminated, and “Yes” indicates that the instrument is contaminated. Results. Scales containing at least one item assessing the spiritual dimension. A = Affective dimension; B = Behavioral dimension; C = Cognitive dimension. Scores range from 0 to 6, with higher scores indicating a more comprehensive validation process. “No” indicates that the instrument is not contaminated, and “Yes” indicates that the instrument is contaminated. The methodological quality and potential risk of bias of the included studies were evaluated through a structured psychometric appraisal system. Given that traditional risk of bias tools (e.g., Cochrane RoB) are designed for interventional studies and not for instrument validation, we applied a specific scoring framework (0–6) based on recognized standards for health measurement instruments. This system allowed us to systematically quantify the certainty of the evidence by assessing six critical domains: content validity, construct validity (CFA), criterion validity, internal consistency, test–retest reliability, and sample adequacy ( Table 3 ). This multidimensional approach ensures that the findings reported for each scale are supported by a rigorous validation process, identifying any potential bias related to small sample sizes or incomplete psychometric reporting. Additionally, a comprehensive search across three major databases with no language restrictions was performed to minimize publication and selection bias.

In recent decades, multiple studies have explored the connection between spirituality and health in fields such as medicine, nursing, psychology, sociology, and theology [ 1 ]. Although initial research focused on religious aspects of healthcare, the growing secularization of societies has broadened interest toward a more inclusive concept of spirituality [ 2 ]. Clinical evidence consistently shows that spirituality can be a key resource for many patients when facing illness, contributing significantly to their quality of life, particularly in those with chronic or advanced conditions [ 3 ]. Conversely, low spiritual well-being or religious struggles have been associated with greater mortality, severe depression, hopelessness, and a desire to die. These findings have led health organizations to recommend the integration of spiritual aspects into clinical care [ 4 ]. Despite this, several challenges persist, including the absence of a universal definition of spirituality and the lack of agreement regarding its dimensions within the health field. This ambiguity has generated multiple interpretations of the construct and has complicated the selection and comparison of instruments used to measure it [ 5 ]. Although related, religiosity and spirituality are not equivalent. Koenig defines religiosity as the adherence to structured systems of beliefs, rituals, and symbols oriented toward the sacred [ 6 ]. In contrast, spirituality is understood as a personal search for meaning and answers to existential questions, as well as a relationship with the sacred or transcendent, with or without participation in organized religion [ 7 ]. Puchalski’s definition highlights spirituality as a dynamic, intrinsic aspect of humanity through which individuals seek meaning, purpose, and transcendence, expressed in relationships with oneself, others, society, nature, and the sacred [ 8 ]. The absence of a consensual definition has contributed to diverse conceptualizations of spirituality, generally grouped into two broad perspectives: a theistic perspective, centered on belief in God or a higher power, and a non-theistic perspective, focused on existential, humanistic, and secular dimensions of human experience [ 7 ]. The working definitions of the constructs of spirituality and religion on which this study was based appear in Table 1 . These definitions served as the conceptual foundation for determining the eligibility of instruments, guiding both the classification of scales and the identification of items that reflect the current spiritual state. To generate solid evidence in this field, precise and validated measurement instruments are essential. However, it remains unclear whether existing tools adequately assess patients’ current spiritual beliefs, attitudes, and needs, or whether they can guide clinical interventions. These limitations hinder the development of a spirituality-integrated model of care [ 12 ]. Although previous reviews have examined spiritual and religious instruments [ 13 , 14 ], recent analyses specifically addressing updated psychometric properties in populations with chronic or advanced illnesses are lacking, despite the fact that these groups rely more frequently on spiritual and religious coping. Furthermore, earlier reviews did not examine instruments from a multidimensional perspective incorporating cognitive, affective, and behavioral domains. Considering these dimensions is crucial, as they represent the main ways in which spirituality is expressed in clinical practice: cognitive (beliefs, interpretations, and meaning attributed to illness and life), affective (emotions such as peace, hope, or existential suffering), and behavioral (actions and practices used to cope with illness). Together, these domains form the basis for evaluating the current spiritual state, a dynamic construct that fluctuates according to an individual’s clinical, emotional, and existential experience [ 13 ]. For the purposes of this review, “current spiritual state” was operationally defined as the individual’s present cognitive, affective, and behavioral spiritual experience, as reflected through validated items capturing spiritual beliefs, emotions, and practices in the here-and-now. Based on this definition, instruments were classified as (1) primary spirituality measures, in which spirituality constitutes the central construct of the scale, and (2) mixed psychosocial instruments, which include a spiritual dimension embedded within a broader psychosocial assessment. The inclusion of mixed instruments is justified because their spiritual subscales provide validated, clinically relevant indicators of current spiritual experience in populations with chronic and advanced illness [ 13 , 15 ]. Given the conceptual and methodological diversity among spirituality instruments, this review proposes an integrative framework combining psychometric analysis with a multidimensional functional classification. This approach allows clinicians and researchers to identify tools most suitable for assessing the current spiritual state and informing patient-centered interventions. Therefore, this systematic review aims to identify, classify, and critically analyze the most widely used and validated instruments for measuring spirituality in clinical contexts, with particular emphasis on their ability to assess the current spiritual state across cognitive, behavioral, and affective dimensions.

A total of 881 articles were identified through searches in PubMed, Scopus, and Web of Science, from which 42 studies were selected that validated 43 instruments for measuring spirituality in clinical settings. Some instruments had abbreviated versions and were validated in different countries, which were considered independent scales. The article selection process is detailed in Figure 1 . To facilitate a clearer understanding of the findings, the results are presented in a structured manner, beginning with the identification and classification of instruments, followed by their psychometric properties, and concluding with an analysis of dimensional patterns across scales. Table 5 shows scales that include at least one item assessing the spiritual dimension. Among others, it shows the correlations observed between these spirituality measures and health outcomes in cross-sectional studies, reflecting their concurrent validity, and available data from prospective studies that analyzed the ability of these instruments to predict health outcomes, demonstrating their predictive validity. As explained in the Section 2 , mixed psychosocial instruments were included when they contained a validated spiritual domain relevant to assessing the current spiritual state. Table 6 presents mixed psychosocial instruments that include at least one validated spiritual item relevant to the assessment of the current spiritual state. The methodological quality of the 43 identified spiritual assessment scales demonstrated a high level of rigor in their development process. All studies ( n = 42, 100%) clearly stated their objectives and described the instrument purpose. Sample sizes ranged from 12 to 897 participants (median = 225), with the majority ( n = 40, 93.02%) meeting recommended minimum sample sizes for psychometric analysis ( n ≥ 100). Most scales reported a comprehensive psychometric evaluation. Content validity was the most frequently reported property ( n = 42, 97.67%), followed by criterion validity ( n = 41, 95.35%) and construct validity through factor analysis ( n = 41, 95.35%). Internal consistency (reliability) was established for 93.02% of the scales ( n = 40). However, responsiveness to change ( n = 4, 9.3%) was the only property with significantly lower reporting, due to the cross-sectional design of most studies. Transparency in reporting was generally adequate, with most studies providing sufficient detail about methods and acknowledging limitations. The quality assessment results are summarized in Table 7 . Overall, while the included studies demonstrated acceptable methodological rigor, there was considerable variability in the comprehensiveness of psychometric evaluation, which should be considered when interpreting the findings. The instrument validated with a larger sample of participants is the Spiritual Wellbeing Scale (FACIT Sp12), which was studied with 897 individuals in Sydney, Australia. Overall, the samples included in the reviewed studies consisted of 64.29% cancer patients; 28.57% patients with chronic diseases such as diabetes or respiratory, cardiac, or renal diseases, and 7.14% consist of studies with a mixed population. The instrument developed with the greatest variability in the sample was the EORTC quality of life, with a sample size of 451 collected in 14 different countries. Five instruments were validated in different populations, and since one of them met the exclusion criteria (such as healthy individuals), it was excluded due to the impossibility of disaggregating the data. The following subset comprises studies offering the most impactful data for clinical application. The validation study of the Lithuanian version of SHALOM cites as a limitation the need for evidence of its concurrent validity, comparing the findings with data from other sources and applying congruent or divergent measurement tools. Concurrent validity is a type of criterion-related validity. In the validation study of the Psychosocial and Spiritual Needs Assessment Instrument for Patients at the End of Life (ENP-E), criterion-related validity was established by correlating the ENP-E scale with other instruments measuring emotional well-being, such as the Hospital Anxiety and Depression Scale (HADS), the Distress Thermometer (DT), and the Quality of Life item (QLQ-15) from the EORTC QLQ-C15-PAL. A positive correlation was observed with the HADS and DT, and a negative correlation with the QLQ-15, supporting the instrument’s sensitivity to emotional and quality-of-life dimensions in end-of-life contexts. Similarly, in the validation of the I-SPIRIT scale, convergent and discriminant validity were assessed by comparing the instrument with the FACIT-Sp, the BMMRS, the POMS, the PHQ-8, and the physical and social/family well-being subscales of the FACT-G. The correlations between the I-SPIRIT factors (Spiritual Needs and Spiritual Resources) and these comparator measures provided evidence for the instrument’s alignment with related constructs (convergent validity) and its distinction from unrelated domains (discriminant validity). In contrast, the validation of the QRFPC questionnaire employed indirect methods, assessing validity by comparing scale scores across patients with varying levels of functional status as measured by the ECOG scale. While this approach linked the instrument’s scores to a clinically relevant variable, it does not constitute a traditional criterion validity assessment involving comparison with an established “gold standard.” The Arabic version of the FACIT-Sp states that the concurrent validity of the FACIT-Sp has been well established in previous studies and that its results are comparable. Pearson correlation coefficients were calculated to estimate the shared variance between the FACT-G subscales and the Spiritual Well-being factors, providing evidence of convergent validity. Regarding predictive validity, we can state that it was scarce since most of the research had cross-sectional designs. Spirituality measurement instruments are often multidimensional and have diverse objectives, such as assessing expressions of spirituality, beliefs, or spiritual experiences. The instruments were classified as measures of spiritual well-being; spiritual resources and coping or support; spiritual needs; professional sensitivity and competence; spiritual experiences; spiritual self-care practices; and as measures of spiritual perspective and related activities. The established classification is based on the definition of three categories of items (cognitive, behavioral, and affective), according to the spiritual expression they attempt to represent. All of the instruments include items that investigate cognitive aspects, 42 of the 43 scales measure affective aspects of spirituality, and 40 of the 43 scales analyze behavioral aspects of spirituality. Overall, 93.02% represented all three categories together. The dimensions that are most repeated among the scales analyzed can be grouped into the following main concepts represented in Figure 2 . Although these concepts are often used, the way they are defined and measured can vary significantly across scales, reflecting the diverse theoretical and cultural approaches to spirituality. Some of these dimensions that are least repeated between the scales are represented in Figure 3 . Focusing on these underrepresented dimensions is crucial, as they capture clinically significant nuances of spiritual distress that frequently surface in patients facing chronic or advanced stages of illness. Factors such as guilt, a loss of inner peace, or the avoidance of thoughts regarding death are well-established predictors of emotional suffering and poor adjustment to disease; nonetheless, they remain largely overlooked by current assessment scales. Similarly, constructs like insecure attachment or intrapersonal spirituality point to deeper identity and relational processes that shape how a patient interprets their situation and manages uncertainty. The scarcity of these indicators in existing tools suggests that many instruments might be missing critical facets of the current spiritual state, thereby hindering the ability to identify specific needs or sources of distress essential for tailored spiritual care. During the analysis of the content and structure of the instruments included in this review, it was identified that several of the scales commonly used to measure spirituality present elements that could be conceptually contaminated; that is, they may suffer from possible tautological problems, including items that overlap with dimensions of psychological, emotional, or social well-being. According to recent literature [ 71 ], this type of overlap may compromise the discriminant validity of the instruments and can induce tautological associations in correlational studies with mental health. Therefore, highlighting these problems could serve as a point of attention to those interested in the area. Among the instruments analyzed in this study, the following scales have been previously reported as contaminated: FACIT-Sp: includes items related to meaning, purpose, inner harmony and comfort. WHOQOL-SRPB: integrates dimensions of mental health, quality of life and social connection. SWBS and SWBQ: potentially contaminated when existential and religious subscales are combined. SIWB: incorporates elements associated with life purpose and emotional well-being. STS: Includes indicators of inner peace, connection, and emotional transcendence. FACIT-Sp: includes items related to meaning, purpose, inner harmony and comfort. WHOQOL-SRPB: integrates dimensions of mental health, quality of life and social connection. SWBS and SWBQ: potentially contaminated when existential and religious subscales are combined. SIWB: incorporates elements associated with life purpose and emotional well-being. STS: Includes indicators of inner peace, connection, and emotional transcendence.

This systematic review aimed to identify and analyze available scales for assessing current spiritual status specifically in adult patients receiving palliative care and adult patients with chronic and advanced illnesses, examining the psychometric properties and validity of these instruments from a three-dimensional perspective (cognitive, behavioral, and affective) to understand how spirituality is measured in these relevant clinical contexts. The identification of a significant number of scales validated in diverse languages and cultures (as evidenced by studies in cancer patients [ 41 , 44 ], and in patients with other chronic diseases [ 46 , 58 ]) underlines the growing attention toward the assessment of spirituality in these specific health domains. When analyzing the psychometric properties of the identified scales, considerable variability in their reliability was observed. For example, the Italian version of the Patient Dignity Inventory (PDI-IT) [ 67 ] demonstrated excellent internal consistency with a Cronbach’s alpha of 0.96. Similarly, the Farsi version of the Spiritual Needs Questionnaire (SpNQ) [ 41 ] reported a Cronbach’s alpha of 0.91 in a sample of 400 cancer patients. These findings suggest adequate reliability in specific populations. However, other scales showed more modest internal consistency, such as the Polish version of the FACIT-Sp-12 [ 56 ], with a Cronbach’s alpha of 0.614 in patients with various chronic diseases. This variability underlines the importance of considering the reliability reported for the population and the context in which the scale is intended to be used, as emphasized by Sánchez and Echeverry [ 27 ]. It is important to clarify that Cronbach’s alpha represents an indicator of internal consistency reliability only. Some of the original validation studies interpreted high alpha coefficients as indirect support for construct coherence, but such values do not constitute evidence of validity. In this review, Cronbach’s alpha was considered exclusively as a measure of reliability, while validity was assessed through distinct psychometric approaches such as factorial analyses or criterion-related evaluations. Regarding validity, most studies focused on construct validity (through exploratory or confirmatory factor analysis) and internal consistency. For example, the Spanish version of the Functional Assessment of Chronic Illness Therapy–Spiritual Well-Being Scale (FACIT-Sp) [ 37 ] demonstrated an acceptable level of reliability, as indicated by McDonald’s Omega coefficient, and its factorial structure was examined in oncology patients. Similarly, the Turkish version of the Spirituality Instrument-27 (SpI-27) [ 58 ] showed a Cronbach’s alpha of 0.927 in cardiology patients, and their study also explored the construct validity. However, an important limitation, consistent with what was reported in the review by Bhagwandas et al. [ 72 ], is the relative scarcity of studies assessing criterion-related validity, especially predictive validity. The ability of these scales to predict relevant health outcomes over time remains an open question in many cases. The diversity of scales identified in this review reflects the complexity and multidimensional nature of the spirituality construct in these specific contexts. The lack of a single, universally accepted definition of spirituality [ 6 ] is manifested in the different approaches taken by the scales we analyzed. The dimensionality of spirituality remains a complex issue, as illustrated by the factorial instability of the SWBS [ 38 ] and the different structures found for the SpNQ in its 27-item Chinese version [ 44 ] compared to the original version. The existence of six dimensions in the SpNQ-Ch-27, influenced by Chinese cultural factors such as avoidance of discussion about death, highlights how cultural factors can shape the expression of spiritual needs. The suggestion to differentiate between the existential and religious aspects of spirituality, based on the study of HHI in patients with non-advanced cancer [ 63 ], also contributes to this debate. In contrast to general spirituality scales, instruments specifically designed to assess spiritual needs (such as the SpNQ, SNAP or I-SPIRIT) demonstrate greater clinical usefulness. These scales include items that identify concrete areas of spiritual suffering, available resources and unmet needs, allowing clinicians to guide individualized interventions and support clinical decision-making in palliative care and chronic illness. Consequently, their clinical value is higher than that of global spirituality scales, whose purpose is more descriptive than diagnostic. This dimensionality could explain the paradox of the existence of many scales for measuring spirituality and their underuse in clinical practice. This contradiction can be understood by another series of interrelated factors evidenced in the literature, such as methodological and psychometric issues, since identified problems of validity, reliability, and cultural bias in many of the tools reviewed. These methodological deficiencies can undermine health professionals’ confidence in the usefulness of the scales for clinical decision-making. Another reason is the disconnect between the scales and clinical needs, since Monod et al. [ 13 ] observed that many spirituality scales have been developed primarily for research purposes and are not designed for use in daily clinical practice. Health professionals may perceive that the existing scales are too long, complex, or irrelevant to their clinical needs, which hinders their adoption in practice. Finally, contextual and practical barriers such as lack of training of health professionals in spiritual assessment, cultural differences in understanding spirituality, and conflicting clinical priorities may also contribute to the underutilization of the scale by Selman et al. [ 15 ]. The concern about “contaminating elements” in spirituality scales [ 71 ] is also relevant in our populations of interest. It is crucial to consider whether items on scales used with patients with chronic illnesses or in palliative care might be influenced by their physical or mental health status (such as depression or fatigue), which could artificially inflate or deflate spiritual well-being scores. This study presents limitations such as the heterogeneity of the validated samples, which makes direct comparison of results across studies difficult and limits the ability to draw universal conclusions about the psychometric properties of spirituality scales. Furthermore, it suggests that the validity and reliability of the scales may vary significantly depending on the specific population, highlighting the need for caution when selecting and applying these instruments in clinical practice and research. Furthermore, we found a predominance of cross-sectional studies. This type of design, although useful for exploring associations between variables at a given time, does not allow for establishing causal relationships or examining the evolution of spirituality over time [ 3 ]. Our findings confirm this limitation, as only 9.3% of the included studies provided evidence of responsiveness to change. In the context of spirituality and health, it is crucial to understand how spirituality influences health outcomes over time and how these outcomes, in turn, may affect the individual’s spirituality. In the specific context of chronic and advanced illness, where spirituality often fluctuates in response to suffering or clinical interventions, this lack of longitudinal validation and sensitivity data represents a major barrier for the integration of these tools into routine clinical follow-up. Finally, the presence of contaminated items may compromise the discriminant validity of the scales, that is, their ability to measure spirituality as a construct distinct from other aspects of well-being. This can lead to tautological associations in correlational studies, where the high correlation between spirituality and mental well-being is partly due to the scales measuring similar constructs. This study also has clear strengths. First, a systematic and structured search was conducted using several databases and complemented by input from experts in the field. Furthermore, the proposed functional classification was validated based on the triple abstraction process conducted by blinded reviewers. Excellent agreement was observed. Additional data from subsequent studies using these instruments (e.g., data on concurrent and predictive validity) were systematically retrieved from the search. Finally, this review was not limited to English-language instruments but also included some measures initially developed in French, German, and Korean. This review may also be limited by potential publication bias, as unpublished validation studies or non-indexed instruments may not have been identified. In addition, the exclusion of studies not published after 2011 may have led to the omission of earlier but still relevant validation work. Given the identification of “contamination” in several spirituality scales, further research is needed to develop and validate scales that minimize this problem and more accurately capture the unique dimensions of spirituality. This entails an effort to refine the conceptual definition of spirituality and to identify items that more purely reflect its essential components. Developing more discriminating scales may require the use of qualitative research methods to explore the experience of spirituality in depth in different populations and the application of advanced statistical techniques, such as confirmatory factor analysis, to validate the structure of the scales and ensure that they measure distinct constructs. Given the limitations imposed by the predominance of cross-sectional studies, it is recommended that future research adopt longitudinal designs, as they allow for the examination of the trajectory of spirituality over time. This is especially relevant in clinical populations where spirituality can fluctuate in response to illness, treatment, and other factors. By conducting repeated measurements of spirituality and health outcomes in the same individuals over time, researchers can identify patterns of change, determine the direction of relationships between variables, and assess the predictive capacity of spirituality in relation to clinical outcomes.

This systematic review provides an overview of the current landscape of spirituality assessment scales relevant to patients with chronic illnesses and palliative care. While various instruments are available, their psychometric quality and validity vary significantly. The identification of potential “contaminating elements” in some widely used scales underscores the need for a cautious interpretation of results and the development of more rigorous and conceptually clear tools. Future research should focus on strengthening the psychometric properties of the scales, especially responsiveness to change, predictive validity, and addressing conceptual challenges to advance our understanding of the role of spirituality in the context of health and healthcare. To advance this field, future studies should prioritize methodologically rigorous validation of spirituality scales, with a focus on clearly defined constructs, hypothesis testing, and the use of longitudinal designs. Addressing these limitations will improve the accuracy and usefulness of spirituality measures in assessing spiritual needs and evaluating the effectiveness of spiritual interventions.