Establishing consensus on the appropriate tool for measuring adherence to glaucoma medication in a sub-Saharan African population: a multidisciplinary Delphi-based study

Establishing consensus on the appropriate tool for measuring adherence to glaucoma medication in a sub-Saharan African population: a multidisciplinary Delphi-based study | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL Public Health Challenges This is a preprint and has not been peer reviewed. Data may be preliminary. 8 July 2025 V1 Latest version Share on Establishing consensus on the appropriate tool for measuring adherence to glaucoma medication in a sub-Saharan African population: a multidisciplinary Delphi-based study Authors : Benjamin Abaidoo 0000-0003-2268-9032 [email protected] , Khathutshelo Percy Mashige , and Pirindhavellie Govender-Poonsamy Authors Info & Affiliations https://doi.org/10.22541/au.175196046.68442282/v1 Published Public Health Challenges Version of record Peer review timeline 187 views 120 downloads Contents Abstract ABSTRACT INTRODUCTION RESULTS DISCUSSION STRENGTHS AND LIMITATIONS CONCLUSIONS Supplementary Material References Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract Background: Despite the availability of various methods for assessing medication adherence, limited guidance exists regarding the most appropriate tool, particularly for measuring glaucoma medication adherence. Objective: To achieve expert consensus on the appropriate tool for measuring glaucoma medication adherence using the Delphi technique. Methods: A two-round Delphi study was conducted with a panel of experts from diverse fields, assessing three validated adherence measurement tools. Consensus was determined using Kendall’s Coefficient of Concordance. The extent of agreement and inter-rater reliability were evaluated using the scale-level content validity index (S-CVI) and intraclass correlation coefficients (ICC), analysed in SPSS version 25. Results: Sixteen experts (mean age 53.8±7.1 years; mean professional experience: 21.9±6.8 years) participated. Consensus levels of 81.0% and 89.0% consensus were achieved in the first and second rounds, respectively. Agreement on non-adherence characteristics was high (SCVI and ICC values > 0.75). The most appropriate tool for measuring non-adherence to glaucoma medication was the Glaucoma Treatment Compliance Assessment Tool-Short form (GTCAT-S) with an S-CVI of 0.91 and ICC of 0.94 (95% CI:0.78-0.99; p = 0.001). Conclusions: The GTCAT-S was identified as the most appropriate tool for measuring non-adherence to glaucoma medication, achieving showed evidence of high SCVI with an excellent inter-rater reliability. Establishing consensus on the appropriate tool for measuring adherence to glaucoma medication in a sub-Saharan African population: a multidisciplinary Delphi-based study Authors: Benjamin Abaidoo 1,2,3 , Khathutshelo Percy Mashige 3 , Pirindhavellie Govender-Poonsamy 3 Institutions 1 Ophthalmology Unit, Department of Surgery, University of Ghana Medical School, Accra, P.O. Box GP 4236, Ghana. 2 Eye Department, Korle Bu Teaching Hospital, Accra. 3 Discipline of Optometry, School of Health Sciences, University of KwaZulu-Natal, Private Bag X54001, Durban 4000, South Africa Corresponding Author: Benjamin Abaidoo Email: [email protected] Ophthalmology Unit, Department of Surgery, University of Ghana Medical School, Accra, P.O. Box GP 4236, Ghana. TEL. NO.: +233277818746 ORCID number: 0000-0003-2268-9032 Disclosures : none Source of funding: This was a self-funded project by the principal investigator. Competing interests: None Journal: Journal of Evaluation in Clinical Practice Acknowledgments The authors thank all the experts and acknowledge their support and input during the Delphi process. Great thanks to the authors and developers of all the tools (GTCAT-S, EDSQ, and GAQ-R) used in the Delphi process. Authors’ contributions B.A. was responsible for conceptualisation, methodology, formal analysis, data collection, and writing of drafts. K.P.M. and P.G-P. were responsible for conceptualisation, methodology, resources, review of drafts, and administration. Data availability The authors confirm that the data supporting the findings of this study are available upon reasonable request through the corresponding author. Disclaimer The views and opinions expressed in this article are those of the authors and are the product of professional research. It does not necessarily reflect the official policy or position of any affiliated institution, funder, agency, or that of the publisher. The authors are responsible for this article’s results, findings, and content. ABSTRACT Background: Despite the availability of various methods for assessing medication adherence, limited guidance exists regarding the most appropriate tool, particularly for measuring glaucoma medication adherence. Objective: To achieve expert consensus on the appropriate tool for measuring glaucoma medication adherence using the Delphi technique. Methods: A two-round Delphi study was conducted with a panel of experts from diverse fields, assessing three validated adherence measurement tools. Consensus was determined using Kendall’s Coefficient of Concordance. The extent of agreement and inter-rater reliability were evaluated using the scale-level content validity index (S-CVI) and intraclass correlation coefficients (ICC), analysed in SPSS version 25. Results: Sixteen experts (mean age 53.8±7.1 years; mean professional experience: 21.9±6.8 years) participated. Consensus levels of 81.0% and 89.0% consensus were achieved in the first and second rounds, respectively. Agreement on non-adherence characteristics was high (SCVI and ICC values > 0.75). The most appropriate tool for measuring non-adherence to glaucoma medication was the Glaucoma Treatment Compliance Assessment Tool-Short form (GTCAT-S) with an S-CVI of 0.91 and ICC of 0.94 (95% CI:0.78-0.99; p = 0.001). Conclusions: The GTCAT-S was identified as the most appropriate tool for measuring non-adherence to glaucoma medication, achieving showed evidence of high SCVI with an excellent inter-rater reliability. Key words: Delphi technique, glaucoma, non-adherence, medication, measurement. INTRODUCTION Adherence to anti-glaucoma medications has a significant impact on managing the disease [1,2]. Measuring adherence to medication is a complex phenomenon and involves both objective and subjective techniques [3-5]. Several tools for measuring non-adherence to glaucoma medication exist but have inherent limitations in addressing different aspects of non-adherence [3-5]. Medication adherence in general is influenced by numerous behavioural factors exhibited by patients [4,6,7]. The European Society of Patient Adherence, Compliance, and Persistence (ESPACOMP) group, divides adherence into three interrelated phases namely; initiation of medication, implementation, and persistence with the medication prescribed [8]. These stages are also influenced by several behavioural factors that includes; the patient’s attributes, the environment of the patient, nature of the disease, and its treatment [4,8]. For this reason, the choice of tools for measuring non-adherence is very crucial as the development of effective and innovative interventions for addressing non-adherence to medication depends on the quality of medication adherence studies [8]. Currently, there is no gold standard method to measure non-adherence to glaucoma medication [9]. According to Farmer [9] and Vermeire et al [10], an ideal tool for measuring non-adherence should be cost effective, user friendly, feasible, highly reliable, and flexible in a busy clinic. However, currently, none of the tools available can meet all these requirements since each tool has its limitations. Considering the multifactorial nature of non-adherence, it is important to have an appropriate tool for measuring non-adherence to glaucoma medication which could also support the assessment of the effectiveness of interventions to mitigate non-adherence. The Delphi technique harnesses experts’ opinions and is useful in resolving situations where there are several multifaceted and interrelated factors with uncertainties [11-13]. Thus, the Delphi technique can be used for consensus-building in situations where literature evidence about the most appropriate tool for measuring adherence is lacking [11]. This technique enables the use of qualitative and quantitative measures to strengthen the in-depth understanding of experts’ opinions and provides a foundation for statistically analysing experts’ consensus [11-13]. The use of the Delphi technique is yet to be explored in selecting appropriate tools for assessing non-adherence behaviours in patients with glaucoma. In this Delphi study, a multidisciplinary and patient-centred approach bringing together patients’ group, eye care providers, health policy planners, and experts from other relevant fields for a consensus on the appropriate tool for measuring non-adherence to glaucoma medications in a sub-Saharan African population was established. METHODS Study design This study used a two-round Delphi iterative consultation design with a panel of experts from various fields to establish consensus on the appropriate tool for measuring non-adherence to glaucoma medication. The principal investigator facilitated the Delphi process. Inclusion criteria The participants were selected based on the perspectives of the patient, the eye care provider, and other key stakeholders in eye care and research. Participants were experts in ophthalmology, pharmacy, health economics, biostatistics, public health, and a representative from the Glaucoma Association of Ghana (a non-governmental organisation for patients with glaucoma in Ghana). Participants had to have at least ten years of experience in their expert fields, a good professional image, and be willing to be part of the process through all the stages and from diverse geographical locations (Africa, Europe and North America). Exclusion criteria Experts from fields other than the fields described in the inclusion criteria, those with less than ten years’ experience in their field of expertise and those unwilling to be part of all the stages of the study, were excluded. Sample size and sampling The sample size was determined based on the study by Cejudo [14], who recommended a minimum of seven participants for a Delphi process. For this study, a panel of 16 experts in the fields described above were included in the process to increase participation. Purposive and snowball sampling techniques were used to select participants. This was done by purposively selecting participants who met the inclusion criteria from the fields of expertise described above after they were approached and the purpose of the study explained to them. Others were also recruited based on recommendations from invited participants (snowball sampling). All participants expressed their interest to participate by consenting. Response rate A minimum of 70% response rate in each round was required to reduce response bias [15]. To increase the response rate in this study, the principal investigator created a cordial rapport with participants through e-mails and telephone communication. Analysis of experts’ competence level The experts’ competence level in this Delphi process was analysed using the K coefficient, an index used in a previous study [15]. This factor was based on experts’ level of knowledge about non-adherence to glaucoma medication using the knowledge assessment domain of the Glaucoma Treatment and Compliance Assessment Tool-Short (GTCAT-S) which included statements such as; my personal knowledge of the symptoms of glaucoma is excellent, a person can have glaucoma and not know it, eye pain is a common symptom of glaucoma, glaucoma treatments can prevent future vision loss, and vision lost from glaucoma is permanent. Responses to these statements were reported in a 5-point Likert-scale from ”disagree a lot - (1)” to ”agree a lot - (5)”. Scores were then computed and converted into percentages. Scores higher than or equal to 80% were classified as competent. Definition of consensus To maintain rigour, Kendall’s W, a non-parametric test which measures the level of agreement for an expert panel, was used as the level of agreement was not normally distributed [15]. For the Kendall’s W, the level of consensus is considered strong where W ≥ 0.7 (70 % or more), moderate 0.50-0.69 (50-69 %) and weak where W < 0.5 (less than 50 %). Data collection methods and tools This Delphi process had three stages, namely, the preliminary stage, the exploratory stage, and the final stage. A coordinating group comprising the principal investigator (BA) and two other co-authors (KPM and PGP) was formed for the preliminary stage. This group selected the top three self-reported glaucoma disease-specific medication adherence measurement tools through a systematic review of glaucoma disease-specific methods for measuring adherence to glaucoma medications. The three tools selected were the Glaucoma Treatment Compliance Assessment Tool-Short form (GTCAT-S) [16], the Eye-Drop Satisfaction Questionnaire (EDSQ) [17], and the revised Glaucoma Adherence Questionnaire (GAQ-R) [18], based on their reasonable predictive power and appropriateness in a resource-limited setting. At the exploratory stage, the selected tools were sent to the panel of experts via e-mail to examine the tools according to the extent of agreement with adherence characteristics. As patient experiences are integral in assessing the reliability of patient-reported outcome measures in health care [19-21], the conceptual foundation of this Delphi technique was supported by an exploratory qualitative study among 24 patients with glaucoma to identify barriers and motivators of adherence to glaucoma medication in a tertiary health facility. Details of this qualitative study are reported elsewhere [22]. From the qualitative study, knowledge about glaucoma, self-efficacy, forgetfulness, missing doses, improper administration of medication, discontinuing medication, barriers to adherence, fear of blindness, perceived benefits from treatment, a good provider-patient relationship were identified as barriers and motivators of adherence. These factors were therefore used in assessing the extent of agreement with adherence characteristics to the three adherence tools. The first round Delphi questionnaire was designed to determine which of the three self-reported adherence tools best meet the factors derived from the qualitative study on a Likert scale (1 to 3; not at all appropriate, somewhat appropriate and very appropriate). The experts were provided with text fields for comments at the end of each question. Responses from the first round were analysed, and comments were documented. Feedback was subsequently sent to the experts. In sequential rounds, the experts reviewed each tool and evaluated the degree of suitability of the items in the tool. During the final stage, the second round Delphi process, the most appropriate tool was selected after establishing consensus. The experts were asked to rate on a Likert scale (1 to 3; not at all appropriate, somewhat appropriate and very appropriate) which tool was most suitable for measuring non-adherence to glaucoma medication in the context of the following factors; reliability and validity, relevance among patients with glaucoma, relevance within an African cultural/population setting, feasibility of implementation in a clinical setting, cost-effectiveness. Text fields were provided at the end of each question for comments to be written. In each round, the K coefficient (the level of consensus) was calculated from the responses provided. A summary of the Delphi Iterative Consultation is illustrated in Figure 1 below. Figure 1. Delphi Iterative Consultation phase for the study. Others refer to the two representatives from the Glaucoma Association of Ghana. Data analysis Descriptive statistics were used to describe the background characteristics of the Delphi experts. Competency levels were analysed using the K coefficient in accordance with the level of knowledge on adherence to glaucoma medication among the participants. The extent of agreement with non-adherence behaviours and the most appropriate tool for measuring adherence to glaucoma medication were examined using the scale level content validity index (S-CVI) and intraclass correlation coefficients (ICC). These indices were calculated based on the scores from the Likert scale ratings, where the critical cut-off point for an agreement was set at two and above (somewhat appropriate and very appropriate) [12]. The S-CVI which measures the content validity of the overall scale was calculated by averaging of all the item level content validity index (I-CVI). The ICC which is a measure of the reliability of the experts’ ratings was computed using reliability analysis with SPSS version 25 (SPSS Inc, Chicago, IL) following a two-way random effect model with multiple raters and an absolute agreement. ICC values less than 0.5 represented poor reliability, 0.5 to 0.75 were moderate reliability, 0.75 to 0.9 were good reliability, and values > 0.90 were excellent reliability [15]. Open-ended responses explaining reasons for responses were content-analysed. The level of significance was set at 5% with a 95% confidence interval. Ethics approval statement The study adhered to the ethical principles outlined in the Helsinki Declaration for medical research involving human subjects. Ethical approval was obtained from the Biomedical Research Ethics Committee of the University of KwaZulu-Natal (BREC/00002965/2021) and the Institutional Review Board of a Teaching Hospital in Ghana (KBTH-IRB/00048/2021). RESULTS Characteristics of the experts Sixteen experts participated in the two-round Delphi study, yielding a response rate of 80%. Their mean age was 53.8±7.1 years (range = 41- 66 years). Nine of the experts (56.3%) were males. The mean years of experience was 21.9±6.8 years (range = 10 - 40 years) and 12 participants were from Ghana. Other characteristics of the experts are shown in Table 1. Table 1. Characteristics of the experts in the Delphi study Sex: Male Female Total 9 7 16 56.3 43.8 100.0 Area of expertise: Ophthalmology Public health Health economics/policy Pharmacy * Others 8 2 2 2 2 50.0 12.5 12.5 12.5 12.5 Country of residence: Ghana India United Kingdom United State of America 12 1 2 1 75.0 6.3 12.5 6.3 Work setting: Academic Health 10 6 62.5 37.5 * Other; representative from the Glaucoma Association of Ghana. Competence level (K) of the experts The value of K calculated was 82% (n= 16). Level of consensus at each stage For this study, a Kendall’s W ≥ 0.7 (70 %) was achieved for each round of the Delphi process. In the first-round survey, 81% consensus was achieved while 89% consensus was achieved in the second round. Extent of agreement with non-adherence characteristics In the first round of the Delphi process, the GTCAT-S had the highest SCVI of 0.90 with an ICC of 0.85 (0.66-0.96; p = 0.001). (Table 2). The GTCAT had an absolute agreement (ICV = 1) in seven domains namely; knowledge about glaucoma, self-efficacy, forgetfulness, missing doses, barriers to adherence, fear of blindness, and a good provider-patient relationship. (Table 2). Knowledge about glaucoma was the only domain with an absolute agreement (ICV = 1) among the experts for all the three adherence tools. (Table 2). From the first-round survey comments, participants alluded that knowledge about glaucoma is an important element in adherence and that patients having adequate knowledge about the disease will feel motivated to purchase and use drops. Two participants mentioned stockpiling which they said is also an important characteristic of non-adherence. Other results are shown in table 2 below. The most appropriate tool for measuring non-adherence to glaucoma medication An absolute agreement (ICV =1) was realized among the experts in the domain of reliability and validity, relevant among patients with glaucoma, and feasibility of implementation in a clinical setting for the GTCAT-S. At the second round, in analysing the most appropriate tool for measuring non-adherence to glaucoma medication adherence, there was a consensus in favour of the GT-CAT-S with an SCVI of 0.91 with ICC value of 0.94 (95% CI:0.78-0.99; p = 0.001) compared to the GAQ-R [SCVI = 0.90; ICC = 0.88 (95% CI:0.57-0.99; p = 0.001)] and the EDSQ [SCVI = 0.86; ICC = 0.78 (95% CI:0.17-0.98; p = 0.016)] respectively. (Table 3). From the second-round survey comments, 4 participants, mentioned that the issue of relevance within an African cultural/population setting was quite difficult to excess because Africa is a huge place with many different cultures, and in some settings folks are happy to say what they think and in others there are huge layers of politeness that preclude true response gathering. Table 2. Extent of agreement with non-adherence characteristics 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 GTCAT Knowledge about glaucoma 3 3 3 3 3 3 3 3 3 2 3 3 3 3 3 3 16 1.00 Self-efficacy 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 16 1.00 Forgetfulness 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 16 1.00 Missing doses 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 16 1.00 Improper administration of medication 2 2 2 2 2 3 3 3 3 3 3 3 3 3 3 3 11 0.69 Discontinuing medication 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 9 0.56 Barriers to adherence 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 16 1.00 Fear of blindness 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 16 1.00 Perceived benefits from treatment 3 3 3 3 3 3 3 3 3 3 3 3 2 2 2 2 12 0.75 A good provider-patient relationship 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 16 1.00 SCVI/mean = 0.90 Intraclass Correlation Coefficient = 0.85 (0.66-0.96; p = 0.001) GAQ-R Knowledge about glaucoma 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 16 1.00 Self-efficacy 3 3 3 3 3 3 3 3 3 3 3 3 3 2 2 2 13 0.81 Forgetfulness 2 3 3 3 3 3 3 3 3 3 2 2 2 2 2 2 9 0.56 Missing doses 2 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 15 0.94 Improper administration of medication 2 2 2 2 2 3 3 3 3 3 3 3 3 3 3 3 11 0.69 Discontinuing medication 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 6 0.38 Barriers to adherence 2 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 15 0.94 Fear of blindness 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 16 1.00 Perceived benefits from treatment 2 2 2 3 3 3 3 3 3 3 3 3 3 3 3 3 13 0.81 A good provider-patient relationship 3 3 3 3 3 3 3 3 3 3 2 2 2 2 2 2 10 0.63 SCVI/mean = 0.78 Intraclass Correlation Coefficient = 0.79 (0.55-0.94; p = 0.001) EDSQ Knowledge about glaucoma 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 16 1.00 Self-efficacy 3 3 3 3 3 3 3 3 3 3 2 2 2 2 2 2 10 0.63 Forgetfulness 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 16 1.00 Missing doses 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 16 1.00 Improper administration of medication 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 9 0.56 Discontinuing medication 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 16 1.00 Barriers to adherence 3 3 3 3 3 3 3 3 3 3 2 2 2 2 2 2 10 0.63 Fear of blindness 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 9 0.56 Perceived benefits from treatment 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 9 0.56 A good provider-patient relationship 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 9 0.56 SCVI/mean = 0.75 Intraclass Correlation Coefficient = 0.82(0.61-0.95; p = 0.001) Table 3. The most appropriate tool for measuring non-adherence to glaucoma medication 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 GTCAT Reliability and validity 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 16 1.00 Relevance among patients with glaucoma 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 16 1.00 Relevance within an African cultural/population setting 3 3 3 3 3 3 3 3 3 3 3 3 3 3 2 2 14 0.88 Feasibility of implementation in a clinical setting 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 16 1.00 Cost effectiveness 2 2 3 3 3 3 3 3 3 3 3 3 3 2 2 2 11 0.69 SCVI/mean = 0.91 Intraclass Correlation Coefficient = 0.94 (0.78-0.99; p = 0.001) GAQ-R Reliability and validity 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 16 1.00 Relevance among patients with glaucoma 2 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 15 0.93 Relevance within an African cultural/population setting 3 3 3 3 3 3 3 3 3 3 3 3 3 3 2 2 14 0.88 Feasibility of implementation in a clinical setting 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 16 1.00 Cost effectiveness 2 2 3 3 3 3 3 3 3 3 3 3 3 2 2 2 11 0.69 SCVI/mean = 0.90 Intraclass Correlation Coefficient = 0.88 (0.57-0.99; P = 0.001) EDSQ Reliability and validity 3 3 3 3 2 2 3 3 3 3 3 3 3 3 3 3 14 0.88 Relevance among patients with glaucoma 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 16 1.00 Relevance within an African cultural/population setting 3 3 3 3 3 3 3 3 3 3 3 3 2 2 2 2 12 0.75 Feasibility of implementation in a clinical setting 3 3 3 3 2 2 3 3 3 3 3 3 3 3 3 3 14 0.88 Cost effectiveness 3 3 3 3 2 2 2 3 3 3 3 3 3 3 3 3 13 0.81 SCVI/mean = 0.86 Intraclass Correlation Coefficient = 0.78 (0.17-0.98; P = 0.016) DISCUSSION Since the Delphi method is used extensively in consensus-based solutions [12], it was applied in this study to determine the most appropriate tool for measuring medication adherence. The extent of agreement with non-adherence characteristics in relation to the tools was high (SCVI and ICC values > 0.75) with 81.0% consensus. The high intraclass correlation coefficients (ICC) in the first round demonstrates that the experts agreed on the importance of the non-adherence characteristics used in assessing the tools. Similar to our findings, a high content validity index with an excellent inter-rater agreement was reported in a study to investigate the content validity of a new patient-reported experience measure. 24 In addition, Almathami et al [25] reported good inter-rater agreement among Delphi participants in identifying factors that influence users’ motivation toward the use of a teleconsultation system. Knowledge about glaucoma was the only domain with an absolute agreement (ICV = 1) among the experts for all three adherence tools, signifying the importance of assessing the level of knowledge in the measurement of adherence. Comments from the first round of the survey revealed that knowledge about glaucoma is an essential element in adherence and that patients having adequate knowledge about the disease will feel motivated to purchase and use their drops. Participants also said that good knowledge about the disease and its complications inspires patients to promote self-care. This suggests the need to consider a tool that can assess the level of knowledge about glaucoma in a quest for the choice of a suitable adherence measurement tool. The high SCVI and ICC values of the GTCAT-S demonstrates excellent validity and reliability of the tool in measuring adherence to glaucoma medication with less disparities among the experts. The constitution of experts with high academic achievements and stakeholders in the management of glaucoma may account for this high inter-rater reliability with less differences among the experts. The COSMIN (Consensus-based Standards for the Selection of Health Status Measurement Instruments) study, through a four-round Delphi survey by international experts made up of psychologists, epidemiologists, statisticians and clinicians, justified the use of the SCVI and the ICC as significant measurement properties in assessing the appropriateness of patient reported-measurement outcomes and the proposal of novel health measurement scales [19-21]. Our results reinforce the need for consensus building in the choice of adherence measurement tools in health care delivery and research. The experts’ agreement for a choice of glaucoma disease-specific adherence measurement tool with excellent reliability, which is sensitive in identifying significant changes in the eye health of persons with glaucoma, also reflects a pragmatic approach to using a tool that will work best in a natural glaucoma clinic setting. The GTCAT-S in various studies has demonstrated acceptable test-retest reliability and internal consistency and wide usage in assessing adherence among glaucoma patients [3,26]. Our findings also build on the evidence that the Delphi technique could offer a more insightful way of making decisions in eyecare practice. Participants mentioned the relevance of the tools within an African cultural/population setting. They indicated that it was difficult to assess because Africa is a large continent with many different cultures, and in some settings, people are comfortable to express their thoughts and in others, there is pragmatic politeness that preclude true response gathering. Future studies should therefore take a critical look at this factor before using it as an assessment criterion. Nevertheless, the experts agreed that the other four factors (reliability and validity, relevance among patients with glaucoma, feasibility of implementation in a clinical setting, and cost effectiveness) were significant in assessing the choice of an appropriate tool for assessing adherence to glaucoma medication. Although our Delphi findings guide the selection of non-adherence measurement instruments, the recommendations for an ideal tool should always be tailored to the specific need to be addressed. This study provides a systematic framework for reviewing and comparing existing adherence measurement tools. Experts in non-adherence measurement have suggested the need to use multiple measurement tools in assessing medication non-adherence in a study [4]. However, this suggestion will work when multiple non-adherence characteristics are the key outcome of interest. The choice of a self-reported measurement tool is essential in not only measuring the level of adherence but also in assessing significant elements of non-adherence, such as reasons for non-adherence, drug affordability, and manual dexterity, among others [12,27]. STRENGTHS AND LIMITATIONS This study adopted a multidisciplinary approach in constituting a heterogenous group of experts with an international composition of experienced eye care providers, health policy planners, patients’ groups, and experts from other relevant fields. This promoted a high level of consensus after the first and second rounds to improve the validity of the results and reflected different views. Anonymity was maintained which prevented group domination and enhanced participation. The sample size was reasonable and the response rate was high for a Delphi study. Despite the above-mentioned strengths, there were limitations that need to be acknowledged. For instance, more time was required to administer the two rounds of the Delphi process in order to consolidate the outputs. Although the study utilised barriers and motivators of non-adherence derived from a qualitative study by persons with glaucoma, the selection of questions submitted to the experts were mostly controlled by the facilitator of the Delphi process. Lastly, although a higher level of agreement was achieved on each domain of the framework for assessing the tools, there was a lack of absolute agreement with most of the non-adherence characteristics. CONCLUSIONS The study identified the GTCAT-S tool as an appropriate tool for measuring non-adherence to glaucoma medication. Consensus was reached with a high intraclass correlation coefficient, demonstrating excellent inter-rater reliability in the process. This outcome will guide clinicians and researchers in choosing the most appropriate tool for measuring adherence. 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Collection Public Health Challenges Keywords adherence delphi technique glaucoma Authors Affiliations Benjamin Abaidoo 0000-0003-2268-9032 [email protected] Korle Bu Teaching Hospital View all articles by this author Khathutshelo Percy Mashige University of KwaZulu-Natal View all articles by this author Pirindhavellie Govender-Poonsamy University of KwaZulu-Natal View all articles by this author Metrics & Citations Metrics Article Usage 187 views 120 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Benjamin Abaidoo, Khathutshelo Percy Mashige, Pirindhavellie Govender-Poonsamy. Establishing consensus on the appropriate tool for measuring adherence to glaucoma medication in a sub-Saharan African population: a multidisciplinary Delphi-based study. Authorea . 08 July 2025. DOI: https://doi.org/10.22541/au.175196046.68442282/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. 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