{"paper_id":"a86e6f7d-fd16-4c10-b01a-3189b2b66b35","body_text":"R E S E A R C H A R T I C L E Open Access\nThe Endometriosis Impact Questionnaire\n(EIQ): a tool to measure the long-term\nimpact of endometriosis on different\naspects of women ’s lives\nMaryam Moradi 1* , Melissa Parker 2, Anne Sneddon 3, Violeta Lopez 4 and David Ellwood 3\nAbstract\nBackground: Endometriosis is a chronic disease impacting on many aspects of a woman ’s life. Because of the\nchronic and recurring nature, many of the impacts of endometriosis could be missed using existing questionnaires\nwhich focus on recent events. Therefore, a questionnaire with a long-term perspective is necessary. This study\naimed to develop and evaluate a questionnaire to measure the long-term impact of endometriosis on different\naspects of women ’s lives.\nMethods: Through a methodological design, phase 1 was qualitative and phase 2 was a cross-sectional study. The\noriginal 100 EIQ items were developed based on results from an earlier qualitative study and literature review.\nThrough a process of assessing face and content validity this was reduced to 66 items. The psychometric properties\nof the final 63 item EIQ were evaluated through a web-based survey with data from 423 responders with a self-\nreported surgically-diagnosed endometriosis.\nResults: Participants were aged 16-58 years. Exploratory factor analysis of a 66-item EIQ was established with 423\nresponders. The final 63-item EIQ contained six dimensions including: 33-item physical-psychosocial; 3-item fertility;\n7-item sexual; 11-item employment; 6-item educational; and 3-item lifestyle. Cronbach ’s alpha of 0.99 for the whole\n63-item EIQ, and 0.84 to 0.98 for the dimensions suggests a very good reliability. High positive correlations between\nthe EIQ and the EHP-5 (altered recall period) indicated good evidence of concurrent validity. High intra-class\ncorrelations indicated very good test-retest reliability.\nConclusions: The EIQ, as a disease-specific questionnaire, could be used to provide a better understanding of the\nimpact of endometriosis on different aspects of life, to better meet the needs of women. We recommend\nadditional studies to establish validity evidence for the EIQ, including studies in other countries and languages.\nKeywords: Endometriosis, questionnaire, psychometrics, reliability, validation study, quality of life\nBackground\nEndometriosis is a high prevalence condition causing\nchronic pelvic pain, and the third leading cause of\ngynaecological hospitalization in the United States with\nhigh rates of hysterectomy [ 1]. Endometriosis requires\nlifelong management [ 2] and treatment must be individ-\nualized, taking into account the entire clinical problem,\nincluding disease impact and effects of treatment on\nquality of life (QoL) [ 3]. The most widely used instru-\nments are the generic Health-Related Quality of Life\n(HRQoL) questionnaire including the Short Form –36\nversion (SF-36) [ 4, 5], the short version of the World\nHealth Organization QoL (WHOQOL-BREF) [ 6, 7], and\nthe EuroQol-5D [ 8]. However, the general HRQoL\nquestionnaires do not consider unique variables related to\nendometriosis such as infertility [ 9] and the impact of\nsymptoms other than pain. There are some specific\nquestionnaires including Endometriosis Health Profile-30\n© The Author(s). 2019 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0\nInternational License ( http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and\nreproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to\nthe Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver\n(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.\n* Correspondence: moradim@mums.ac.ir; maryam.moradi.fu@gmail.com\n1Nursing and Midwifery Care Research Center, Mashhad University of Medical\nSciences, Mashhad, Iran\nFull list of author information is available at the end of the article\nMoradi et al. BMC Women's Health           (2019) 19:64 \nhttps://doi.org/10.1186/s12905-019-0762-x\n\n(EHP-30) [ 10]a n di t ss u b s e t ,t h eE H P - 5[ 11], Endo-\nmetriosis Treatment Satisfaction Questionnaire\n(ETSQ) [ 12], daily electronic Endometriosis Pain and\nBleeding Diary (EPBD) [ 13], and ‘Patient-Centred\nEndometriosis ’ q u e s t i o n n a i r eo fE n d oC a r eQ u e s t i o n -\nnaire (ECQ) [ 14] but the EHP-30 is currently the\ndisease-specific questionnaire to measure the HRQoL\nw i t ht h es t r o n g e s tv a l i d i t ye v i d e n c e[9].\nPublished studies assessed the impact of endometriosis\non pain using the VAS, depression using the BDI or\nHAM-D, anxiety using STAI or HAM-A [ 7], work\nimpairment using WPAI [ 5, 8], sexual satisfaction using\nGRISS [ 6] and the GSSI [ 15], and sexual function using\nthe FSDS or FSFI [ 16], and DSFI [ 15]. There is limited\nresearch on the psychological impacts of endometriosis\nexcept for depression/anxiety, work, education, social\nlife, and lifestyle.\nExisting tools only asses a subset of QOL indicators,\nand measure disease impact with a perspective of four\nweeks or less. Due to the chronic, recurring nature of\nendometriosis, many disease impacts could be missed,\nso a multi-dimensional questionnaire with a longer-term\nperspective is necessary to provide a better understand-\ning. Women ’s perceptions of the impact of endometri-\nosis have been explored through our earlier qualitative\nstudy [ 17]. We have now developed and evaluated the\npsychometric properties of a questionnaire to measure\nthe longer-term impact of endometriosis on different\naspects of women ’s lives.\nMethods\nThe Endometriosis Impact Questionnaire (EIQ) is a\nself-report questionnaire which asks women how\nendometriosis has affected their lives over the three\nrecall periods including ‘last 12 months ’, ‘1 to 5 years\nago’ and ‘more than 5 years ago ’. Categorical responses\nfor all EIQ items are ranked using a 5 point Likert scale\nincluding: 0 = Not at all, 1 = A little, 2 = Somewhat, 3 =\nQuite a lot, 4 = Very much and 9 = Not applicable. Each\nitem contributes equally and higher scores indicate a\ngreater impact. The EIQ was developed and a psycho-\nmetric evaluation conducted, using face, content,\nconstruct (factor analysis), concurrent validity, and reli-\nability (internal consistency and test-retest reliability).\nThe study used a methodological design which involved\nthe development and evaluation of data collection\ninstruments, scales or techniques [ 18]. To evaluate\nconstruct and concurrent validity and reliability, a\ncross-sectional study was conducted via a web-based\nsurvey. The development process is illustrated in Figure 1.\nAll data were analyzed using SPSS version 20, and a prob-\nability values of p< 0.05 were considered to be statistically\nsignificant.\nDeveloping the items of the EIQ\nThe original 100 EIQ items were developed from a\nqualitative study [ 17] and from a systematic literature\nreview. Eight steps on scale development [ 19], and the\ncriteria for selecting items [ 20], were followed. The\nreadability of the EIQ based on the Fog index [ 21] and\n‘Readability Formulas ’ [22] were used. In addition,\nendometriosis patients and experts were asked to evalu-\nate readability of items [ 21].\nEvaluating the psychometric properties\nValidity\nThe adequacy of a scale as a measure of a specific\nvariable is an issue of validity [ 19]. The initial\n100-item EIQ was evaluated to delete repeated items\nor those which related to only a few women from the\nf o c u sg r o u p sd i s c u s s i o n s[17], so it was reduced to 89\nitems.\nFace validity\nFeedback was sought from 12 patients and 14 health\nprofessionals with expertise in endometriosis, question-\nnaires development, chronic disease, and psychology.\nThey reviewed the 89-item EIQ and answered three\nopen questions; 1. Does this appear to be a good\nmeasure of the impact of endometriosis? 2. List any areas\npertinent to the impact of that are not covered 3. Share\nwith us your feedback or any other comments to improve\nthe EIQ.\nContent validity\nFor the content validity index (CVI) [ 21], we asked the\nsame 12 patients and 14 health professionals to review\nthe 89-item EIQ and rate the items based on ‘Relevance’,\n‘Clarity’ and ‘Simplicity’ on a four-point scale. The CVI\nwas measured as a percentage of the items rated as 3 or\n4[ 23, 24]. Item-level content validity index (I-CVI) was\ncomputed as the number of experts giving a rating of ei-\nther 3 or 4, divided by the total number of experts [ 25].\nA CVI or S-CVI of 0.80 was considered as indicating ac-\nceptability [ 23]. Following these steps the EIQ was\nreduced to 66 items.\nConstruct validity\nThe initial EIQ had randomly-ordered items to avoid\nhypothesised factor structure. But considering the\nnumber of items and the three recall periods,\nrandom-ordering made the EIQ difficult and time\nconsuming to complete. Some experts suggested\narranging the items in logical groups rather than having\nthe items all mixed up, to make it easier to complete by\nresponders. Therefore, the initial EIQ with randomly-or-\ndered items was divided into logical groups based on\ncategories which emerged from results of an earlier\nMoradi et al. BMC Women's Health           (2019) 19:64 Page 2 of 11\n\nqualitative study [ 17], but the main categorizing of the\nEIQ was made based on exploratory factor analysis. The\n66-item EIQ was then subjected to exploratory factor\nanalysis to assess construct validity [ 26]. The commonly\nused method of principal component analysis and vari-\nmax rotation was used [ 27]. For this study, the accept-\nable level for factor loading was equal to or greater than\n0.40 [ 28], and eigenvalues greater than one [ 27] were\nconsidered. The required sample size was estimated at\n350 to 400 to have subject-to-variable ratio of 5:1, which\nidentified as adequate in most cases [ 26].\nConcurrent validity\nThere is no comparable questionnaire with a long-term\nperspective so to assess concurrent validity the EHP-5\n[11] was chosen and the recall period changed from the\n‘last 4 weeks ’ to ‘last 12 months ’.\nReliability\nTwo frequently used indicators of a scale ’s reliability, in-\ncluding internal consistency (Cronbach ’s alpha) and\nstability (Pearson correlation coefficient (r), test-retest\nreliability) were evaluated [ 26].\nInternal consisten3cy reliability\nStrong item-total correlations were identified as above\n0.30 and inter-item correlations as ranging 0.30-0.70\n[29]. In this study, a Cronbach ’sa l p h a≥ 0.7 was consid-\nered satisfactory and a corrected item-to-total correlation\nof at least 0.3 was considered as acceptable.\nTest-retest reliability\nTo determine test-retest reliability, two copies of the\nfinal version were posted to 70 patients, who completed\na first copy on the day that they received it, and a\nsecond copy after two weeks. Statistical differences\nbetween the two scores were assessed.\nSample and setting\nConvenience and snowball sampling were used to recruit\na sufficiently large number of accessible participants,\nwith an emphasis on those residing in Australia. Inclu-\nsion criteria were self-reported surgically-diagnosed\nendometriosis and ability to understand English. A\nweb-based survey was conducted and recruitment was\nthrough different strategies from secondary or tertiary\ncare levels, as well as from the general community. The\nEIQ-link was widely advertised via flyers disseminated or\nposted. Many groups and people (like endometriosis\ncentres and endometriosis support groups) were asked\nto assist by forwarding an invitation email to their\ndatabases and/or by putting flyers in their centres or on\ntheir website/Facebook pages.\nPilot study\nA pilot study was conducted for the EIQ paper version\nand then for the EIQ online version. The EIQ paper\nversion was finalized and pilot tested with eight patients\nin July 2013 and all responders provided positive feed-\nback, stating that “It is comprehensive ” and “It is clear ”.\nThe online EIQ was developed using ANU Polling\nOnline (APOLLO) in August 2013 (Link: https://apollo.\nanu.edu.au/default.asp?pid=7700) and was pilot tested\nwith four patients in September 2013. Feedback was\ngenerally positive stating that “It worked fine ” and “The\ninstructions are very clear ”.\nResults\nEIQ item generation\nThe first draft of the EIQ included 100 items which re-\nduced to 89. Face validity, content validity and further\nFig. 1 Development process of the EIQ\nMoradi et al. BMC Women's Health           (2019) 19:64 Page 3 of 11\n\nrevisions resulted in a decrease to 66 items, and this ver-\nsion was used to assess factor analysis, concurrent valid-\nity, and test-retest reliability. Through factor analysis,\nthree items were deleted and 63 items formed the final\nEIQ (Additional file 1).\nDemographic and clinical characteristics of responders\nA total of 484 responders completed the final 63-item\nversion between September 2013 and February 2014.\nOne was excluded for providing incorrect completion;\nall 483 remaining questionnaires were fully completed.\nA further 60 responders were excluded as they did not\nhave surgically-diagnosed endometriosis. Data from the\nremaining 423 responders were used to assess the\npsychometric properties of the EIQ. Demographic and\nclinical characteristics are provided in Table 1.\nReadability of the EIQ\nGunning Fog Index was 8.7 for the 66-item EIQ and 8.6\nfor the 63-item EIQ, both of which are considered as\n‘fairly easy to read ’. Based on seven readability formulae\nthe EIQ was scored as grade level 6, which means a\nstandard/average reading level suitable for readers aged\n10-11 years (fifth and sixth graders).\nFace validity\nMost believed that the EIQ was ‘comprehensive’ and a\n‘good’ measure of the impact of endometriosis. Only one\npatient and four of the experts reported that the 89-item\nEIQ was too long and suggested reviewing it for redun-\ndant items.\nContent validity\nContent validity of the 89-item EIQ was based on seven\nout of 14 experts and six out of 12 patient ’s ratings. The\ninter-rater agreements were 0.84 (experts) and 0.93\n(patients). S-CVI and I-CVIs indicated acceptable\ncontent validity for both the EIQ and its items.\nAlthough, based on I-CVIs only two out of 89 items\nrequired deletion or change, a further 21 items were\ndeleted to shorten to 66 items; these were items that\noverlapped, or had a low score on clarity or simplicity.\nConstruct validity\nA sample size of 423 was adequate for factor analysis\nbased on a Kaiser-Meyer-Olkin (KMO) test result of\nmore than 0.9 and a Bartlett ’s test of sphericity that was\nsignificant (p < 0.01). An inspection of the scree plot re-\nvealed a break after six or seven factors. All items with a\nfactor loading of 0.4 and above were retained. The\nresults from the factor analysis of the EIQ and each of\nthree recall periods including ‘last 12 months ’, ‘1 to 5 years\nago’ and ‘more than 5 years ago ’ were consistent to sup-\nport having six separate factors for physical-psychosocial,\nfertility, sexual, employment, educational and lifestyle.\nThe exception was that in the ‘more than 5 years ago ’\nperiod some of the physical items were loaded into a\nseparate factor. However, to have consistent factor dimen-\nsions, it was decided to include the physical items into the\nphysical-psychosocial dimension. Factor analysis with six\nfactors explained 58.14, 53.84, 52.86, and 46.09 of the total\nvariance in recall period of ‘last 12 months ’, ‘1 to 5 years\nago’, ‘more than 5 years ago ’, and the total EIQ respectively.\nThree items were removed from the 66-item EIQ because\nthey did not reach a 0.4 factor loading. In comparison with\nthe primary EIQ categorizing, factor analysis identified a\nnew dimension which was called fertility, combined the\nphysical, psychological and social items into one factor\ncalled physical-psychosocial, and transferred some items\nbetween dimensions.\nFinal EIQ\nThe final EIQ with 63 items had six dimensions: (1)\nphysical-psychosocial - 33 items (consisting of physical –\n13 items, psychological- 16 items and social impact – 4\nitems); (2) fertility - 3 items; (3) sexual - 7 items; (4) em-\nployment - 11 items; (5) educational - 6 items; and (6)\nlifestyle - 3 items (Additional file 1).\nConcurrent validity\nThere were statistically significant high positive correla-\ntions ( r=0.66-0.80, (n=423), p < 0.01) between the ‘last\n12 months ’ of the EIQ and the EHP-5 (Table 2), indicat-\ning that patients who experienced a greater impact\n(higher EIQ score) had worse health-related quality of\nlife (higher score from the EHP-5). Therefore, the recall\nperiod of ‘last 12 months ’ for the EIQ, had high concur-\nrent validity or very good correlation with the EHP-5.\nCorrelations were good ( r = 0.40-0.58) when the EHP-5\nwas compared with the ‘1 to 5 years ago ’ period of the\nEIQ, and medium or low ( r= 0.17-0.45) when compared\nwith the ‘more than 5 years ago ’ period of the EIQ,\nexcept for sexual dimension and intercourse module,\nwhich was good at a level of p= 0.45.\nEIQ Scoring\nThe score for each dimension at each recall period was\nthe sum of all applicable items divided by the maximum\nscore, rescaled to 0-100. The total score for each dimen-\nsion was calculated as a mean of the three recall periods.\nIf responders skipped a dimension or recall period,\nbecause they were not applicable to them, a score for\nthat dimension or recall period could not be calculated.\nAn SPSS code was provided to score the EIQ. The for-\nmula for scoring the EIQ and its dimensions on a scale\nfrom 0-100 was the sum of the scores of the applicable\nitems multiplied 100/the maximum score of the applic-\nable items, which was the number of applicable items x\nMoradi et al. BMC Women's Health           (2019) 19:64 Page 4 of 11\n\nTable 1 Demographic and clinical characteristics of women\nwith endometriosis ( n=423)\nCharacteristics n (%)\nAgea (years) 32.64± 8.38,\n(Range: 16-58)\nAge groups Aged 16-24 75 (17.73)\nAged 25-34 186 (43.97)\nAged 35 and\nabove\n162 (38.30)\nCountry of birth Australia 313 (74.00)\nOther 110 (26.00)\nCountry at time of doing the EIQ Australia 351 (82.98)\nOther 72 (17.02)\nLanguage is spoken at home English 418 (98.82)\nOther 5 (1.18)\nMarital status Married 187 (44.21)\nIn a relationship 129 (30.50)\nNever married 48 (11.35)\nSingle 45 (10.64)\nSeparated/\nDivorced\n13 (3.07)\nWidowed 1 (0.24)\nEducational level Primary or high\nschool\n14 (3.31)\nLower secondary\nschool\n22 (5.20)\nUpper secondary\nschool\n47 (11.11)\nVocational\n(e.g. TAFE)\n79 (18.68)\nSome college/\nuniversity\n42 (9.93)\nTertiary,\nundergraduate\n131 (30.97)\nTertiary,\npostgraduate\n76 (17.97)\nOther 12 (2.84)\nEmploymentb Not employed 43 (10.17)\nPaid work, full\ntime\n200 (47.28)\nPaid work, part\ntime\n119 (28.13)\nHome duties 47 (11.11)\nStudent, full time 30 (7.09)\nStudent, part time 22 (5.20)\nRetired 3 (0.71)\nOther 38 (8.98)\nPregnancy history b Never pregnant 237 (56.03)\nOne or more\nchildren\n126 (29.79)\nMiscarriage or\nstillbirth\n64 (15.13)\nTable 1 Demographic and clinical characteristics of women\nwith endometriosis ( n=423) (Continued)\nCharacteristics n (%)\nCurrently\npregnant\n10 (2.36)\nDelayed fertility Not applicable\n(never tried)\n194 (45.86)\nNo 69 (16.31)\nYes 160 (37.83)\nAge at onset of symptoms a (years) 16.35± 5.21,\n(Range: 8-42)\nAge at first visit to doctor a (years) 19.70±6.49,\n(Range: 9-43)\nAge at diagnosis a (years) 24.65± 6.58,\n(Range: 12-43)\nDelay in diagnosis a (years) 8.31±6.58,\n(Range: 0-28)\nEndometriosis-related symptoms b\n(life time).\nPeriod pain 420 (99.29)\nFatigue 397 (93.85)\nBloating 386 (91.25)\nPelvic pain not\nrelated to periods\n382 (90.31)\nOvulation/mid\ncycle pain\n377 (89.13)\nPain during/after\nsex\n354 (83.69)\nHeavy bleeding 345 (81.56)\nIrregular bleeding 271 (64.07)\nDelayed fertility 158 (37.35)\nOther 91 (21.51)\nEndometriosis treatments b\n(life time)\nPain killers 410 (96.93)\nSurgical\ntreatments\n394 (93.14)\nHormonal\nmedications\n368 (87.00)\nComplementary\ntreatments\n208 (49.17)\nHormonal IUD 175 (41.37)\nPsychologist 120 (28.37)\nNutritionist 95 (22.46)\nPhysiotherapist 72 (17.02)\nSexual therapist 15 (3.55)\nOther 48 (11.35)\nTimes presented to emergency\ndepartment due to endometriosis\nNever 165 (39.01)\n1-2 118 (27.90)\n3-4 55 (13.00)\n5-10 44 (10.40)\nMore than 10 41 (9.69)\nHysterectomy due to endometriosis No 376 (88.89)\nYes 47 (11.11)\naMean±SD\nbParticipants were asked to tick all that apply\nMoradi et al. BMC Women's Health           (2019) 19:64 Page 5 of 11\n\n4. The dimensions were scored on a scale from 0\n(minimum possible impact), to 100 (maximum possible\nimpact) as measured by the EIQ.\nThe EIQ scores for the sample as a whole, and the\ndistribution of the scores are reported in Table 3.A t\neach recall period, and also over a total of three recall\nperiods, the highest impact of endometriosis was on fer-\ntility followed by the physical-psychosocial dimension,\nand the lowest impact was on the lifestyle dimension.\nCompletion time of the EIQ\nThe estimated completion time for the 66 item EIQ was\n4.8-31.5 minutes with a mean ± SD of 15.2 ± 6.2\nminutes.\nReliability\nThe internal consistency reliability of the 63-item EIQ and\nthe six dimensions was Cronbach ’s alpha 0.98 (T able 4).\nResults showed good reliability in all dimensions but the\nphysical-psychosocial dimension had the highest and the\nlifestyle dimension had the lowest Cronbach ’s alpha for all\nthree recall periods.\nIn the 63-item EIQ, all items correlated to total items\nat a level above 0.3 except for item numbered Q41,\nwhich correlated to total items at a level of 0.2. Cronba-\nch's alpha for each recall period of the EIQ was 0.97\nacross the 63 items, indicating very good reliability. In\neach recall period, all items correlated to total items at a\nlevel above 0.3 except for two items, which correlated to\ntotal items at a level of 0.2. Within each dimension in\neach recall period, all items correlated to total items at a\nlevel above 0.3.\nResults of the inter-scale correlation matrix is shown\nin Table 5. Only responders who answered for both di-\nmensions were included. All correlations were positive\nand statistically significant and there were high correla-\ntions between most dimensions at all recall periods.\nTest-retest reliability (stability)\nTest retest reliability using intra-class correlation (ICC)\nwas conducted in 40 out of 70 (60%) respondents who\ncompleted the second test after a two-week interval\nusing the EIQ paper version. The results showed a sta-\ntistically significant ICC between all dimensions at times\none and 2, ranging from 0.88-0.99. The results indicate\nthat the EIQ has very good test-retest reliability.\nDiscussion\nThis study shows that the EIQ is a valid, reliable tool to\nmeasure the impact of endometriosis on women ’s lives\nwith a long-term view. Endometriosis is a chronic\ndisease as symptoms may continue despite seemingly ad-\nequate treatment [ 30]. Considering its recurring nature,\nthere are some impacts that could be missed by only\nlooking at the last four weeks. For example, current\nquestionnaires are not able to measure the impacts on a\nwoman who lost her sexual-intimate relationship or who\nwas not able to complete studies and/or work goals, loss\nof job or promotion opportunities, or addressed her re-\ngrets from living with endometriosis. These impacts\nwere revealed during our earlier qualitative study [ 17]\nand are supported by others [ 31, 32]. The EIQ is the first\nquestionnaire to measure multi-dimensional impacts\nwith a long-term view.\nValidation of a scale involves the collection of empir-\nical evidence concerning its use 26. Similar to the EIQ,\nthe ETSQ [ 12] and the EPBD [ 13] were developed from\nfocus group discussions and interviews with patients.\nItems of the EHP-30 were generated based on\nopen-ended exploratory interviews with 25 women with\nendometriosis [ 10]. The process used to validate the EIQ\nwas to some extent similar to the one employed for the\nECQ [ 14], however the development processes were\ndifferent.\nCompared with the EHP-30 [ 10], the EIQ has two new\nsubscales of education and lifestyle, whilst the EHP-30\nhas subscales of relationship with children, medical\nprofessionals, and treatment. Little is known about the\nimpacts of endometriosis on lifestyle but negative\nimpacts were reported during our earlier study [ 17]. Fu-\nture studies should be conducted to measure the impact\nof endometriosis on lifestyle, as well as education and\nTable 2 Concurrent validity correlations of the ‘last 12 months ’ EIQ dimensions with the EHP-5 scales ( n = 423)\nEIQ (last 12 months) EHP-5 Number Pearson Correlation a\nPhysical-psychosocial EHP-5 (score from 5 core items) 412 .80\nPhysical Pain 407 .66\nPsychological Q2,3, & 5 of the core questionnaire b 409 .75\nSocial Social support 402 .64\nSexual Intercourse 363 .71\nFertility Infertility 348 .66\nEmployment Work 360 .66\naAll Correlations were significant at the 0.01level (2-tailed) using Pearson Correlation\nbControl & powerlessness, emotional wellbeing and self-image\nMoradi et al. BMC Women's Health           (2019) 19:64 Page 6 of 11\n\nTable 3 Descriptive statistics of the EIQ dimension scoring\nEIQ dimensions Last 12 months 1 to 5 years ago More than 5 years ago Total three recall periods\nPhysical-Psychosocial\nMean ± SD 62.69 ± 27.25 64.27 ± 23.90 56.12 ± 24.90 61.10 ± 21.28\nNumber a 412 418 401 390\nMinimum (%) .00 (1.9) .00 (1.4) .00 (.9) 6.31 (.9)\nMaximum (%) 100.00 (1.9) 100.00 (1.9) 100.00 (1.4) 100.00 (1.4)\n25 44.70 50.00 38.11 46.81\nPercentile 50 68.56 68.94 58.00 63.52\n75 85.61 82.58 75.38 77.28\nPhysical\nMean ± SD 62.46 ± 27.38 64.46 ± 23.61 58.93 ± 24.50 61.88±20.51\nNumber 407 416 400 384\nMinimum (%) .00 (2.6) .00 (2.1) .00 (.9) 8.97 (.2)\nMaximum (%) 100.00 (4.3) 100.00 (4.0) 100.00 (3.5) 100.00 (1.4)\n25 46.15 51.92 40.91 47.09\nPercentile 50 68.75 67.31 61.54 63.46\n75 84.62 81.25 76.92 76.28\nPsychological\nMean ± SD 65.00 ± 27.89 66.21 ± 25.07 57.26 ± 27.31 62.76 ± 22.89\nNumber 409 416 389 375\nMinimum (%) .00 (1.9) .00 (2.4) .00 (3.5) 1.56 (.2)\nMaximum (%) 100.00 (4.0) 100.00 (3.8) 100.00 (3.3) 100.00 (1.7)\n25 48.44 50.00 39.06 46.15\nPercentile 50 71.88 72.60 59.38 67.19\n75 87.50 84.38 78.59 79.69\nSocial\nMean ± SD 54.81 ± 34.89 56.01 ± 32.20 47.23 ± 32.67 52.44 ± 29.09\nNumber 402 407 373 352\nMinimum (%) .00 (11.3) .00 (8.5) .00 (11.6) .00 (4.3)\nMaximum (%) 100.00 (16.8) 100.00 (13.9) 100.00 (10.6) 100.00 (5.9)\n25 25.00 31.25 18.75 29.17\nPercentile 50 62.50 56.25 43.75 54.17\n75 87.50 81.25 75.00 76.56\nSexual\nMean ± SD 47.24 ± 28.65 47.87 ± 27.93 40.88 ± 29.89 45.53 ± 26.77\nNumber 375 381 343 320\nMinimum (%) .00 (3.5) .00 (3.8) .00 (1.9) .00 (.2)\nMaximum (%) 100.00 (5.4) 100.00 (3.8) 100.00 (1.9) 100.00 (2.4)\n25 25.00 25.00 44.70 22.92\nPercentile 50 50.00 46.43 68.56 44.05\n75 67.86 71.43 85.61 67.86\nFertility\nMean ± SD 70.23 ± 37.59 67.78 ± 36.86 58.24 ± 38.90 65.28 ± 32.70\nNumber 391 390 347 323\nMinimum (%) .00 (13.2) .00 (11.3) .00 (14.7) .00 (4.0)\nMoradi et al. BMC Women's Health           (2019) 19:64 Page 7 of 11\n\nwork which extend beyond time off and lost productivity\naddressed in previous studies [ 5, 8].\nThe demographic and medical characteristics of the\nresponders in this study are consistent with endometri-\nosis patients in previous research, increasing the\ngeneralizability of results. In a multinational study [ 5],\n745 participants had a mean age of 32.5 years and a\nmean delay in diagnosis of 6.7 years, similar to the mean\nage (32.6) and delay (8.3) in this study. In an online\nsurvey most of 8008 patient (from China, France and\nRussia) were diagnosed within five years [ 33].\nThirty-eight percent of EIQ responders had delayed fer-\ntility, consistent with the infertility rate of 37% among\n6,146 European patients [ 34] and 42.5% among 7,020 US\npatients [ 35]. Eleven percent had a hysterectomy because\nof endometriosis, which is within the range of 8-29%\nreported by others [ 36].\nThe self-reporting characteristic of the EIQ has pros\nand cons. Sensitive information is more frequently and\naccurately reported in self-administered modes than\nwhen interviewers ask the questions [ 37]. However, limi-\ntations related to reporting and recall errors may apply\nbecause of the self-reported and retrospective nature of\nthe EIQ. Questionnaire developers can overestimate\npeople’s ability to recall past events [ 20]. However, life\ntime recall period has been used previously with satisfac-\ntory psychometric characteristics [ 14]. The decision to\nhave three recall periods was based on focus group\nTable 3 Descriptive statistics of the EIQ dimension scoring (Continued)\nEIQ dimensions Last 12 months 1 to 5 years ago More than 5 years ago Total three recall periods\nMaximum (%) 100.00 (46.1) 100.00 (41.1) 100.00 (27.0) 100.00 (18.9)\n25 37.50 37.50 25.00 33.33\nPercentile 50 91.67 83.33 66.67 75.00\n75 100.00 100.00 100.00 97.22\nEmployment\nMean ± SD 43.89 ± 34.77 43.66 ± 32.78 35.24 ± 32.40 41.04 ± 30.42\nNumber 385 392 357 334\nMinimum (%) .00 (10.2) .00 (6.4) .00 (11.3) .00 (2.4)\nMaximum (%) 100.00 (9.0) 100.00 (6.9) 100.00 (5.2) 100.00 (3.5)\n25 11.36 15.91 8.71 14.20\nPercentile 50 36.36 34.69 25.00 32.95\n75 75.00 72.67 60.56 64.58\nEducational\nMean ± SD 46.61 ± 39.32 45.48 ± 35.76 43.99 ± 33.71 43.78 ± 31.28\nNumber 173 206 241 149\nMinimum (%) .00 (10.2) .00 (8.5) .00 (6.6) .00 (2.4)\nMaximum (%) 100.00 (7.1) 100.00 (7.1) 100.00 (6.1) 100.00 (2.4)\n25 2.08 8.33 12.50 16.67\nPercentile 50 45.83 43.75 37.50 38.89\n75 83.33 79.17 75.00 70.83\nLifestyle\nMean ± SD 16.54 ± 23.88 20.48 ± 26.78 20.75 ± 28.76 19.43 ± 24.44\nNumber 391 397 367 342\nMinimum (%) .00 (46.6) .00 (43.0) .00 (42.6) .00 (29.8)\nMaximum (%) 100.00 (2.4) 100.00 (2.8) 100.00 (3.5) 100.00 (1.7)\n25 .00 .00 .00 .00\nPercentile 50 .00 8.33 8.33 8.33\n75 25.00 33.33 33.33 33.33\naNumber of responders for whom that dimension at that recall period was applicable. Regarding the total scores, if responders skipped one of the recall periods,\nthe total score for that dimension was not calculated\nThe scores were calculated on a scale from 0-100; a higher score means a greater impact of endometriosis on that dimension of life. 0=Minimum impact of\nendometriosis as measured by the EIQ; 100= maximum possible impact of endometriosis as measured by the EIQ\nOut of 423 responders, 26 (6.1%) participants skipped items from the sexual dimension, 26 (6.1%) participants skipped items from the employment dime nsion,\n152 (35.9%) participants skipped items from the education dimension, and 8 (1.9%) participants skipped items from the fertility and lifestyle dimen sions\nMoradi et al. BMC Women's Health           (2019) 19:64 Page 8 of 11\n\ndiscussions where women reported fluctuations in the\nimpacts, variety of symptoms at different times, and dif-\nfering perceptions of impacts based on their situation,\ndesires, responsibilities and plans [ 17]. It is acknowl-\nedged that using multiple time frames might complicate\nthe questionnaire and overburden respondents but the\ncompletion time of the EIQ was reasonable.\nApplications of the EIQ\nUse of disease-specific instruments in endometriosis\nresearch has been highlighted and preferred in recent\nliterature reviews [ 9, 38]. The EIQ, as a disease-specific\nquestionnaire, could be used to provide detailed infor-\nmation on the multi-dimensional impacts of endometri-\nosis in population health surveys, to compare different\nareas and stages of patients ’ lives or different manage-\nment options. It could be used with all three recall\nperiods or each period independently, because each has\nsatisfactory validity and reliability. The total score for\neach dimension at three recall periods, for all dimen-\nsions at each recall period and the total impact score\ncould be calculated. Combining the scores will depend\nTable 4 Internal consistency of the 63-item EIQ and its dimensions\nNumbera last 12 months 1 to 5 years ago more than 5 years ago \" Total three recall periods\nEIQ total 423 .97 (63 items) .97 .97 .98(189 items)\nPhysical-psychosocial 423 .97 (33 items) .96 .95 .98 (99 items)\nPhysical 423 .92 (13 items) .90 .90 .94 (39 items)\npsychological 423 .95 (16 items) .93 .92 .96 (48 items)\nSocial 423 .91 (4 items) .90 .88 .93 (12 items)\nSexual 397 .84 (7 items) .85 .86 .93 (21 items)\nFertility 415 .73 (3 items) .73 .66 .85 (9 items)\nEmployment 397 .94 (11 items) .94 .94 .97 (33 items)\nEducational 271 .93 (6 items) .92 .91 .93 (18 items)\nLifestyle 415 .53 (3 items) .57 .62 .84 (9items)\naOnly responders who skipped all items of the dimension (all three recall periods) were omitted\nTable 5 Inter-scale correlation matrix for the last 12 months, 1 to 5 years ago, More than 5 years ago\nPhysical-psychosocial Sexual Fertility Employment Educational Lifestyle\nPhysical-Psychosocial 1.00\nSexual .63 a 1.00\n.64b\n.63c\nFertility .41 a .29a 1.00\n.37b .24b\n.47c .33c\nEmployment .74 a .53a .31a 1.00\n.72b .54b .24b\n.70c .55c .35c\nEducational .59 a .43a .16a .72a 1.00\n.60b .47b .20b .69b\n.62c .45c .27c .70c\nLifestyle .37 a .32a .13a .31a .30a 1.00\n.38b .28b .13b .31b .33b\n.48c .44c .17c .43c .32c\nPearson correlation coefficient (r) was evaluated\naLast 12 months: All Correlations were significant at the 0.01level (2-tailed) except for fertility-education and fertility-lifestyle, which were significant at the 0.05\nlevel (2-tailed)\nb1 to 5 years ago: All correlations were significant at the 0.01level (2-tailed) except for fertility-lifestyle, which was significant at the 0.05 lev el (2-tailed)\ncMore than 5 years ago: All correlations were significant at the 0.01level (2-tailed)\nMoradi et al. BMC Women's Health           (2019) 19:64 Page 9 of 11\n\non the research objectives. Using the recall period of\n‘last 12 months ’, could be used in clinical trials and to in-\nvestigate outcomes. It could be useful to guide develop-\nment of an individualized disease management plan, and\ncould help patients to communicate with health profes-\nsionals and contribute to such a plan. It could also be\nused as a burden-estimation or needs assessment tool to\nprovide information for making health policy decisions\nto improve services.\nStrengths of this study\nThe EIQ was developed from focus group discussions,\nalong with an extensive literature review, which ensured\nthat the items are relevant to patients from either ter-\ntiary care or the community. A sample of 423, reflected\n6.41 responders per item, is close to being a ‘very good ’\nsample size [ 39]. There were no missing data as most\nitems were compulsory in the online EIQ, but even\nthose who answered the paper version for the test-retest\ndid not miss any questions. The online questionnaire fa-\ncilitated access to women within and beyond Australia,\nwhich was time and expense-saving.\nLimitations of this study\nNon-probability sampling decreases the ability to\ngeneralize results. Dissemination of the study link was\nfocused inside Australia and 74% of responders to the\nonline EIQ were born in Australia. Therefore, the applic-\nability to Australian women with different characteristics\nto the participants, and non-Australians might be lim-\nited. Limitations related to reporting and recall errors\nmay apply. As a web-based survey was used, the general-\nizibility of the results is restricted to those who are key-\nboard and Internet literate [ 40]. In addition, the current\nstudy did not collect clinical information regarding the\nseverity of endometriosis lesions and the existence of co-\nmorbidities, such as mood disorders, obesity, musculo-\nskeletal and neuropathic sources of pain, and patients\nundergoing treatment with psychotropic drugs that\ncould also contribute to symptoms, and it is acknowl-\nedged that not knowing these clinical characteristics of\nthe sample could limit the generalizability of the\nfindings.\nConclusions\nThe EIQ has been developed and validated to measure\nthe impacts of endometriosis on different aspects of\nwomen’s lives with a long-term view. It can be used by\nresearchers and clinicians to provide a better under-\nstanding of the impact of endometriosis on different as-\npects of life over time, and to meet the needs of women\nliving with this condition. We recommend additional\nstudies to establish stronger psychometric properties in-\ncluding known-groups validity and sensitivity to change\nfor the ‘last 12 months ’ section. Further validity evidence\nis also recommended in clinically relevant subgroups of\nendometriosis patients, such as women presenting for\nfertility evaluations versus women presenting with\nchronic pelvic pain, as well as endometriosis patients\nwith the comorbid conditions. Studies in other countries\nand languages are recommended to make multinational\nstudies possible.\nAdditional file\nAdditional file 1: 63-item EIQ. (PDF 428 kb)\nAbbreviations\nEIQ: Endometriosis Impact Questionnaire; HRQoL: Health-Related Quality of\nLife; QoL: Quality of life\nAcknowledgements\nThis article has been derived from a thesis submitted for the degree of\nDoctor of Philosophy at the Australian National University Medical School.\nWe thank the participants for completing the questionnaire (EIQ) and\nhelping us to make this study possible. We acknowledge the experts who\nprovided valuable comments and feedback about the EIQ and many\norganizations and people who helped this study by disseminating the online\nquestionnaire link.\nEthical considerations and consent to participate\nApprovals were obtained from the ACT Health Human Research Ethics\nCommittee (ETH.6.13.155), and from the ANU Human Research Ethics\nCommittee. The first page of the EIQ included a brief information form, and\nit was stated that “Completing this questionnaire is voluntary. By completing\nthe questionnaire you are indicating your consent to participate in the\nstudy”. Online EIQ was an anonymous web-based survey, and could be\ncompleted without a log in.\nCompeting of interests\nThe authors declare that they have no competing interests.\nFunding\nThis research, including design of the study; collection, analysis, and\ninterpretation of data; and the writing of the manuscript, has been\nsupported by the Australian National University (ANU), School of Medicine\nwithin a PhD candidature.\nAvailability of data and materials\nThe datasets generated and analysed during the current study and more\ninformation regarding using the EIQ or scoring details will be available from\nthe corresponding author on reasonable request.\nAuthors’ Contributions\nMM, MP, AS, VL and DA jointly contributed to the study design, analysis\nand interpreting of data. MM and MP identified potential participants\nand recruited the participants. MM developed the online questionnaire.\nMM and VL completed analysis. MM and DA drafted the manuscript.\nMM, MP, AS, VL and DA revised the manuscript critically and approved\nthe final manuscript.\nConsent for publication\nNot applicable.\nPublisher’sN o t e\nSpringer Nature remains neutral with regard to jurisdictional claims in\npublished maps and institutional affiliations.\nMoradi et al. BMC Women's Health           (2019) 19:64 Page 10 of 11\n\nAuthor details\n1Nursing and Midwifery Care Research Center, Mashhad University of Medical\nSciences, Mashhad, Iran. 2Endometriosis Clinic, Canberra Hospital, Canberra,\nAustralia. 3Griffith University, School of Medicine, Queensland, Australia.\n4Yong Loo Lin School of Medicine, National University of Singapore,\nSingapore, Singapore.\nReceived: 23 July 2018 Accepted: 3 May 2019\nReferences\n1. Abbott J, Bowyer L, Finn M. Obstetrics & gynaecology: an evidence-based\nguide. 2nd ed. Churchill Livingstone: Elsevier; 2014.\n2. 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J Am Med Inform Assoc.\n2000;7(4):426–9.\nMoradi et al. BMC Women's Health           (2019) 19:64 Page 11 of 11","source_license":"CC0","license_restricted":false}