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Objective: The European Organisation for Research and Treatment of Cancer (EORTC) core questionnaire, QLQ-C30, is a frequently used patient-reported outcome (PRO) instrument to assess health-related quality of life of patients with cancer. To enhance the understanding and interpretation of PRO data, it is important to obtain norm data from the general population. This article presents updated general population norm data for the EORTC QLQ-C30 for Germany., Methods: Data were obtained as part of a larger study collecting EORTC QLQ-C30 norm data across 15 countries via an online survey. After linear transformation of EORTC QLQ-C30 raw scores, data were weighted based on the United Nations' population distribution statistics. Data are presented by age and sex/age., Results: A total of 1006 Germans responded to the survey. Across EORTC QLQ-C30 domains, different response patterns were observed, with men generally scoring better, that is, higher in most function scales and lower in most symptom scales/items than women. For age, mixed patterns were observed. While older respondents scored worse/lower in physical and role functioning, emotional functioning scores appeared to increase with increasing age. For the symptom scales/items, some symptoms were relatively stable across age groups, while others either increased or decreased with increasing age., Conclusions: This study presents updated EORTC QLQ-C30 general population norm data for Germany that can readily be used for comparative purposes with data obtained from patients with cancer., Competing Interests: Conflict of interest statement None declared., (Copyright © 2020 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Purpose: The aim of this study was to develop and ensure the content validity of a new patient-reported outcome measure, the Cancer Patient Empowerment Questionnaire (CPEQ), to measure the level of, desire for, and enablement of empowerment among cancer patients in follow-up., Methods: An iterative process based on: (i) empowerment theories by Zimmerman and Tengland, (ii) a systematic review of questionnaires measuring empowerment or related concepts among cancer patients, (iii) qualitative data from 18 semi-structured interviews with Danish cancer patients in follow-up, (iv) input from a group of eight cancer patients involved as co-researchers and from an expert steering group, and (v) cognitive interviews with 15 cancer patients in follow-up., Results: The items for the CPEQ were developed and revised and 12 versions of the questionnaire were evaluated. The final version consists of 67 items, covering three different dimensions of empowerment: (A) empowerment outcomes consisting of three components: (A1) the intrapersonal-, (A2) interactional-, and (A3) behavioral component, (B) empowerment facilitators (enablement), and (C) the value of empowerment., Conclusions: This study documents the theoretical and empirical basis for the development of the CPEQ and its content validity. The CPEQ provides a tool for researchers to assess the level of, desire for, and enablement of empowerment among cancer patients. The next steps will be to use the CPEQ in a nationwide study of empowerment in cancer follow-up and subsequently shorten the CPEQ based on psychometric methods in order to make it more relevant in clinical studies.

Background: The assessment of patients' quality of life (QOL) is essential when evaluating the outcome of palliative care; however, no instruments have been validated for measuring symptoms and QOL in patients receiving palliative care in Chile. We aimed to investigate the content validity of the EORTC Quality of Life Questionnaire Core 15 Palliative Care (QLQ-C15-PAL), replicating the methods used previously to shorten the EORTC Quality of Life Questionnaire Core 30 (QLQ-C30) for use among patients in palliative care., Methods: This cross-sectional study was conducted from October to November 2017 in four palliative care services. Patients with advanced cancer and health care professionals (HCPs) were invited to individual interviews to determine the relevance, appropriateness and relative importance of the 30 items of the QLQ-C30 for evaluating the outcome of palliative care, and whether relevant additional issues should be included., Results: A total of 48 patients and 35 HCPs participated. The most important dimensions selected were pain, physical functioning, sleeping difficulties, emotional functioning, nausea/vomiting, fatigue, social functioning, lack of appetite, role functioning and constipation. Qualitative data identified important additional issues not covered by the questionnaire such as satisfaction with care, emotions and psychological support, as well as linguistic issues in the dyspnea and constipation items., Conclusions: The EORTC QLQ-C15-PAL showed good content validity in the assessment of symptoms and QOL of advanced cancer patients; therefore, we recommend the use of this questionnaire in palliative care in Chile. Dyspnea and constipation items were revised by the EORTC group. More research is needed to add a social dimension for a comprehensive assessment of patients' QOL.

Background: The European Organisation for Research and Treatment of Cancer (EORTC) Quality of Life Group (QLG) has developed computerised adaptive tests (CATs) for the 14 functional and symptom domains of the EORTC QLQ-C30 quality of life questionnaire. This is expected to optimise measurement precision, relevance to patients and flexibility. Here, we present the first international validation of the EORTC CAT Core., Methods: A heterogeneous sample of 699 cancer patients scheduled for chemotherapy and/or radiotherapy was recruited across seven European countries. The EORTC CAT Core and all QLQ-C30 items were administered to participants before and after initiating treatment. Correlations between CAT and QLQ-C30 scores and floor/ceiling effects were calculated. Using several grouping variables, relative validity (cross-sectional known groups difference), responsiveness (changes over time) and relative sample size requirements of the CAT compared to the QLQ-C30 were estimated., Results: Correlations of the CAT and QLQ-C30 ranged from 0.81 to 0.93 across domains. The mean relative reduction in floor and ceiling effects using the CAT was 42% (range 3-99%). Analyses of known groups validity and responsiveness indicated that, across domains, mean sample size requirements for the CAT were 72% and 70%, respectively, of those using the QLQ-C30., Conclusions: The EORTC CAT Core measures the same domains as the QLQ-C30 with reduced floor/ceiling effects. The CAT generally facilitated the use of smaller samples (about 30% smaller on average) without loss of power compared to the QLQ-C30. Based on this study, the EORTC QLG will release the EORTC CAT Core for general use.

Introduction: The EORTC QLQ-CR29 is a patient-reported outcome measure to evaluate health-related quality of life among colorectal cancer patients in research and clinical practice. The aim of this systematic review was to investigate whether the initial positive results regarding the measurement properties of the QLQ-CR29 are confirmed in subsequent studies., Methods: A systematic search of Embase, Medline, PsycINFO, and Web of Science was conducted to identify studies investigating the measurement properties of the QLQ-CR29 published up to January 2019. For the 11 included studies, data were extracted, methodological quality was assessed, results were synthesized, and evidence was graded according to the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) methodology on the measurement properties: structural validity, internal consistency, reliability, measurement error, construct validity (hypothesis testing, including known-group comparison, convergent and divergent validity), cross-cultural validity, and responsiveness., Results: Internal consistency was rated as "sufficient," with low evidence. Reliability was rated as "insufficient," with moderate evidence. Construct validity (hypothesis testing; known-group comparison, convergent and divergent validity) was rated as "inconsistent," with moderate evidence. Structural validity, measurement error, and responsiveness were rated as "indeterminate" and could therefore not be graded., Conclusion: This review indicates that current evidence supporting the measurement properties of the QLQ-CR29 is limited. Additionally, better quality research is needed, taking into account the COSMIN methodology.

Purpose: The EORTC IN-PATSAT32 is a patient-reported outcome measure (PROM) to assess cancer patients' satisfaction with in-patient health care. The aim of this study was to investigate whether the initial good measurement properties of the IN-PATSAT32 are confirmed in new studies., Methods: Within the scope of a larger systematic review study (Prospero ID 42017057237), a systematic search was performed of Embase, Medline, PsycINFO, and Web of Science for studies that investigated measurement properties of the IN-PATSAT32 up to July 2017. Study quality was assessed, data were extracted, and synthesized according to the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) methodology., Results: Nine studies were included in this review. The evidence on reliability and construct validity were rated as sufficient and of the quality of the evidence as moderate. The evidence on structural validity was rated as insufficient and of low quality. The evidence on internal consistency was indeterminate. Measurement error, responsiveness, criterion validity, and cross-cultural validity were not reported in the included studies. Measurement error could be calculated for two studies and was judged indeterminate., Conclusion: In summary, the IN-PATSAT32 performs as expected with respect to reliability and construct validity. No firm conclusions can be made yet whether the IN-PATSAT32 also performs as well with respect to structural validity and internal consistency. Further research on these measurement properties of the PROM is therefore needed as well as on measurement error, responsiveness, criterion validity, and cross-cultural validity. For future studies, it is recommended to take the COSMIN methodology into account.

Background: The European Organisation of Research and Treatment of Cancer (EORTC) Quality of Life Group is developing computerized adaptive testing (CAT) versions of all EORTC Quality of Life Questionnaire (QLQ-C30) scales with the aim to enhance measurement precision. Here we present the results on the field-testing and psychometric evaluation of the item bank for cognitive functioning (CF)., Methods: In previous phases (I-III), 44 candidate items were developed measuring CF in cancer patients. In phase IV, these items were psychometrically evaluated in a large sample of international cancer patients. This evaluation included an assessment of dimensionality, fit to the item response theory (IRT) model, differential item functioning (DIF), and measurement properties., Results: A total of 1030 cancer patients completed the 44 candidate items on CF. Of these, 34 items could be included in a unidimensional IRT model, showing an acceptable fit. Although several items showed DIF, these had a negligible impact on CF estimation. Measurement precision of the item bank was much higher than the two original QLQ-C30 CF items alone, across the whole continuum. Moreover, CAT measurement may on average reduce study sample sizes with about 35-40% compared to the original QLQ-C30 CF scale, without loss of power., Conclusion: A CF item bank for CAT measurement consisting of 34 items was established, applicable to various cancer patients across countries. This CAT measurement system will facilitate precise and efficient assessment of HRQOL of cancer patients, without loss of comparability of results.

Background: Role functioning (RF) as a core construct of health-related quality of life (HRQOL) comprises aspects of occupational and social roles relevant for patients in all treatment phases as well as for survivors. The objective of the current study was to improve its assessment by developing a computer-adaptive test (CAT) for RF. This was part of a larger project whose objective is to develop a CAT version of the EORTC QLQ-C30 which is one of the most widely used HRQOL instruments in oncology., Methods: In accordance with EORTC guidelines, the development of the RF-CAT comprised four phases. Phase I involved the conceptualization of RF. In Phase II, a provisional list of items was defined and revised by experts in the field. In phase III, feedback was obtained from cancer patients in various countries. Phase IV comprised field testing in an international sample, calibration of the item bank, and evaluation of the psychometric performance of the RF-CAT., Results: Phases I-III yielded a list of 12 items eligible for phase IV field-testing. The field-testing sample included 1,023 patients from Austria, Denmark, Italy, and the UK. Psychometric evaluation and item response theory analyses yielded 10 items with good psychometric properties. The resulting item bank exhibits excellent reliability (mean reliability = 0.85, median = 0.95). Using the RF-CAT may allow sample size savings from 11 % up to 50 % compared to using the QLQ-C30 RF scale., Conclusions: The RF-CAT item bank improves the precision and efficiency with which RF can be assessed, promoting its integration into oncology research and clinical practice.

Objective: To improve measurement precision, the European Organisation for Research and Treatment of Cancer (EORTC) Quality of Life Group is developing an item bank for computerized adaptive testing (CAT) of emotional functioning (EF). The item bank will be within the conceptual framework of the widely used EORTC Quality of Life questionnaire (QLQ-C30)., Study Design and Setting: On the basis of literature search and evaluations by international samples of experts and cancer patients, 38 candidate items were developed. The psychometric properties of the items were evaluated in a large international sample of cancer patients. This included evaluations of dimensionality, item response theory (IRT) model fit, differential item functioning (DIF), and of measurement precision/statistical power., Results: Responses were obtained from 1,023 cancer patients from four countries. The evaluations showed that 24 items could be included in a unidimensional IRT model. DIF did not seem to have any significant impact on the estimation of EF. Evaluations indicated that the CAT measure may reduce sample size requirements by up to 50% compared to the QLQ-C30 EF scale without reducing power., Conclusion: On the basis of thorough psychometric evaluations, we have established an EF item bank of 24 items. This will allow for more precise and flexible measurement of EF, while maintaining backward compatibility with the QLQ-C30 EF scale., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Purpose: Patient-reported outcomes should ideally be adapted to the individual patient while maintaining comparability of scores across patients. This is achievable using computerized adaptive testing (CAT). The aim here was to develop an item bank for CAT measurement of the pain domain as measured by the EORTC QLQ-C30 questionnaire., Methods: The development process consisted of four steps: (1) literature search, (2) formulation of new items and expert evaluations, (3) pretesting and (4) field-testing and psychometric analyses for the final selection of items., Results: In step 1, we identified 337 pain items from the literature. Twenty-nine new items fitting the QLQ-C30 item style were formulated in step 2 that were reduced to 26 items by expert evaluations. Based on interviews with 31 patients from Denmark, France and the UK, the list was further reduced to 21 items in step 3. In phase 4, responses were obtained from 1103 cancer patients from five countries. Psychometric evaluations showed that 16 items could be retained in a unidimensional item bank. Evaluations indicated that use of the CAT measure may reduce sample size requirements with 15-25% compared to using the QLQ-C30 pain scale., Conclusions: We have established an item bank of 16 items suitable for CAT measurement of pain. While being backward compatible with the QLQ-C30, the new item bank will significantly improve measurement precision of pain. We recommend initiating CAT measurement by screening for pain using the two original QLQ-C30 pain items. The EORTC pain CAT is currently available for "experimental" purposes.

Objective: To evaluate the extent of differential item functioning (DIF) within the thyroid-specific quality of life patient-reported outcome measure, ThyPRO, according to sex, age, education and thyroid diagnosis., Study Design and Setting: A total of 838 patients with benign thyroid diseases completed the ThyPRO questionnaire (84 five-point items, 13 scales). Uniform and nonuniform DIF were investigated using ordinal logistic regression, testing for both statistical significance and magnitude (∆R(2) > 0.02). Scale level was estimated by the sum score, after purification., Results: Twenty instances of DIF in 17 of the 84 items were found. Eight according to diagnosis, where the goiter scale was the one most affected, possibly due to differing perceptions in patients with auto-immune thyroid diseases compared to patients with simple goiter. Eight DIFs according to age were found, of which 5 were in positively worded items, which younger patients were more likely to endorse; one according to gender: women were more likely to report crying, and three according to educational level. The vast majority of DIF had only minor influence on the scale scores (0.1-2.3 points on the 0-100 scales), but two DIF corresponded to a difference of 4.6 and 9.8, respectively., Conclusion: Ordinal logistic regression identified DIF in 17 of 84 items. The potential impact of this on the present scales was low, but items displaying DIF could be avoided when developing abbreviated scales, where the potential impact of DIF (due to fewer items) will be larger.

Purpose: Fatigue is one of the most common symptoms associated with cancer and its treatment. To obtain a more precise and flexible measure of fatigue, the EORTC Quality of Life Group has developed a computerized adaptive test (CAT) measure of fatigue. This is part of an ongoing project developing a CAT version of the widely used EORTC QLQ-C30 questionnaire., Methods: Based on the literature search and evaluations by experts and patients, 41 new fatigue items were developed (in addition to the three QLQ-C30 fatigue items). Psychometric properties of the items, including evaluations of dimensionality, fit to item response theory (IRT) model, and differential item functioning (DIF), were assessed in an international sample of cancer patients., Results: Responses were obtained from 1,321 cancer patients coming from eight countries. Factor analysis showed that 37 of the items could be included in a unidimensional model (RMSEA = 0.098, TLI = 0.995, CFI = 0.920). Of the 37 items, two were deleted because of poor fit to the IRT model forming the basis for the CAT, and one because of DIF between cancer sites., Conclusions: We have established a 34-item fatigue bank allowing for more precise and flexible measurement of fatigue, while still being backward compatible with the QLQ-C30 fatigue scale.

Purpose: To investigate the statistical fit of alternative higher order models for summarizing the health-related quality of life profile generated by the EORTC QLQ-C30 questionnaire., Methods: A 50% random sample was drawn from a dataset of more than 9,000 pre-treatment QLQ-C30 v 3.0 questionnaires completed by cancer patients from 48 countries, differing in primary tumor site and disease stage. Building on a "standard" 14-dimensional QLQ-C30 model, confirmatory factor analysis was used to compare 6 higher order models, including a 1-dimensional (1D) model, a 2D "symptom burden and function" model, two 2D "mental/physical" models, and two models with a "formative" (or "causal") formulation of "symptom burden," and "function.", Results: All of the models considered had at least an "adequate" fit to the data: the less restricted the model, the better the fit. The RMSEA fit indices for the various models ranged from 0.042 to 0.061, CFI's 0.90-0.96, and TLI's from 0.96 to 0.98. All chi-square tests were significant. One of the Physical/Mental models had fit indices superior to the other models considered., Conclusions: The Physical/Mental health model had the best fit of the higher order models considered, and enjoys empirical and theoretical support in comparable instruments and applications.

Purpose: Patients' perceptions of care including the communication with health care staff is recognized as an important aspect of the quality of cancer care. Using mixed methods, we developed and validated a short instrument assessing this communication., Methods: Based on focus group interviews with 77 informants, an 8-item instrument was developed. This short instrument aimed at assessing overall aspects of the communication between cancer patients and health care staff. The items were validated first through cognitive interviews with patient-observer agreement with 52 cancer patients who completed the questions and then participated in tape-recorded open-ended interviews. Observer ratings of the interviews were compared with the patients' written responses collected before interviews and kappa values were calculated. The comprehensibility of each item was subsequently elaborated in traditional cognitive interviews with 17 cancer patients. Finally, psychometric analyses took place with data from 1490 cancer patients., Results: The weighted kappas concerning patient-observer agreement ranged 0.31-0.88. Disagreements mainly consisted of the observer choosing the response category indicating the highest level of satisfaction whereas the patients had chosen the second highest level. Cognitive interviews showed that the questions were generally interpreted as intended. One item was excluded due to low validity. A sum scale of the remaining seven items had high reliability (Cronbach's alpha 0.89)., Conclusions: Seven items performed well. They proved to be valid measures of satisfaction with communication with the health care staff and constitute a sum scale with high reliability. The cognitive interviews provided valuable insight into the patients' perception of communication., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Introduction: Within an ongoing project of the EORTC Quality of Life Group, we are developing computerized adaptive test (CAT) measures for the QLQ-C30 scales. These new CAT measures are conceptualised to reflect the same constructs as the QLQ-C30 scales. Accordingly, the Fatigue-CAT is intended to capture physical and general fatigue., Methods: The EORTC approach to CAT development comprises four phases (literature search, operationalisation, pre-testing, and field testing). Phases I-III are described in detail in this paper. A literature search for fatigue items was performed in major medical databases. After refinement through several expert panels, the remaining items were used as the basis for adapting items and/or formulating new items fitting the EORTC item style. To obtain feedback from patients with cancer, these English items were translated into Danish, French, German, and Spanish and tested in the respective countries., Results: Based on the literature search a list containing 588 items was generated. After a comprehensive item selection procedure focusing on content, redundancy, item clarity and item difficulty a list of 44 fatigue items was generated. Patient interviews (n = 52) resulted in 12 revisions of wording and translations., Discussion: The item list developed in phases I-III will be further investigated within a field-testing phase (IV) to examine psychometric characteristics and to fit an item response theory model. The Fatigue CAT based on this item bank will provide scores that are backward-compatible to the original QLQ-C30 fatigue scale.

Introduction: Differential item functioning (DIF) analyses are commonly used to evaluate health-related quality of life (HRQoL) instruments. There is, however, a lack of consensus as to how to assess the practical impact of statistically significant DIF results., Methods: Using our previously published ordinal logistic regression DIF results for the Fatigue scale of a HRQoL instrument as an example, the practical impact on a particular Norwegian clinical trial was investigated. The results were used to determine the difference in mean Fatigue scores assuming that the same trial was conducted in the UK. The results were then compared with published information on what would be considered a clinically important change in scores., Results: The item with the largest DIF effect resulted in differences between the mean English and Norwegian Fatigue scores that, although small, could be considered clinically important. Sensitivity analyses showed that larger differences were found for shorter scales, and when the proportions in each response category were equal., Discussion: Our scenarios suggest that translation differences in an item can result in small, but clinically important, differences at the scale score level. This is more likely to be problematic for observational studies than for clinical trials, where randomised groups are stratified by centre.

The European Organisation for Research and Treatment of Cancer (EORTC) QLQ-C30 is one of the most widely used quality of life instruments for cancer patients. The aim of this study was to assess whether there were linguistic differences in the way an international sample answered the EORTC QLQ-C30 questionnaire. Thirteen translations of the EORTC QLQ-C30, representing 22 countries, were investigated using a database of 27,891 respondents, incorporating 103 separate studies. Differential item functioning (DIF) analyses were conducted using logistic regression to identify items which, after controlling for subscale, were answered differently by language of administration. Both uniform and non-uniform DIF were assessed. Although most languages showed similar results to English, at least one instance of statistically significant DIF was identified for each translation, and a few of these differences were large. In some cases, the patterns were supported by the results of qualitative interviews with bilingual people. Although, overall, there appeared to be good linguistic equivalence for most of the EORTC QLQ-C30 items, several scales showed strongly discrepant results for some translations. Some of these effects are large enough to impact on the results of clinical trials. Based on our experience in this study, we suggest that validation of translations of health-related quality of life instruments should include exploration of DIF.

Background: The main objective of this study was to investigate the construct validity of the WHOQOL-BREF by use of Rasch and Item Response Theory models and to examine the stability of the model across high/low scoring individuals, gender, education, and depressive illness. Furthermore, the objective of the study was to estimate the reference data for the quality of life questionnaire WHOQOL-BREF in the general Danish population and in subgroups defined by age, gender, and education., Methods: Mail-out-mail-back questionnaires were sent to a randomly selected sample of the Danish general population. The response rate was 68.5%, and the sample reported here contained 1101 respondents: 578 women and 519 men (four respondents did not indicate their genders)., Results: Each of the four domains of the WHOQOL-BREF scale fitted a two-parameter IRT model, but did not fit the Rasch model. Due to multidimensionality, the total score of 26 items fitted neither model. Regression analysis was carried out, showing a level of explained variance of between 10 and 14%. The mean scores of the WHOQOL-BREF are reported as normative data for the general Danish population., Conclusion: The profile of the four WHOQOL-BREF domains is a more adequate expression of quality of life than the total score of all 26 items. Although none of the subscales are statistically sufficient measures of their domains, the profile scores seem to be adequate approximations to the optimal score.

We used general population data (n = 4084) to examine data completeness, response consistency, tests of scaling assumptions, and reliability of the Danish SF-36 Health Survey. We compared traditional multitrait scaling analyses to analyses using polychoric correlations and Spearman correlations. The frequency of missing values was low, except for elderly people and people with lower levels of education. Response consistency was high and compared well with results for the U.S. SF-36. For respondents with computable scales in all eight domains, scaling assumptions (item internal consistency, item discriminant validity, equal item-own scale correlations, and equal variances) were satisfactory in the total sample and in all subgroups. The SF-36 could discriminate between levels of health in all subgroups, but there were skewness, kurtosis, and ceiling effects in many subgroups (elderly people and people with chronic diseases excepted). Concerning correlation methods, we found interesting differences indicating advantages of using methods that do not assume a normal distribution of answers as an addition to traditional methods.

In clinical trials with a quality of life (QoL) component, it is usual to monitor several QoL dimensions at several points in time. Multiple significance tests without formal hypotheses are problematic. It is not always feasible to specify a priori hypotheses for all variables. Can such studies be used to generate hypotheses for testing in later research only? We developed a method which can allow for formal hypothesis testing on a data set collected without a priori hypotheses in the protocol. We surveyed experienced physicians and nurses treating patients, to obtain independent expectations about differences in QoL dimensions. These 'staff expectations' will be used in the analysis of QoL data collected from breast cancer patients taking part in three randomized trials of adjuvant therapy. We propose frameworks for the informal and formal use of the experience of the staff in testing for group differences in patients' QoL scores. The method described here is anticipated to be useful for QoL studies in general, even when a priori hypotheses were specified before the studies were initiated.

Quality of Life (QOL) questionnaires contain two different types of items. Some items, such as assessments of symptoms of disease, may be called causal indicators because the occurrence of these symptoms can cause a change in QOL. A severe state of even a single symptom may suffice to cause impairment of QOL, although a poor QOL need not necessarily imply that a patient suffers from all the symptoms. Other items, for example anxiety and depression, can be regarded as effect indicators which reflect the level of QOL. These indicators usually have a more uniform relationship with QOL, and therefore a patient with poor QOL is likely to have low scores on all effect indicators. In extreme cases it may seem intuitively obvious which items are causal and which are effect indicators, but often it is less clear. We propose a model which includes these two types of indicators and show that they behave in markedly different ways. Formal quantitative methods are developed for distinguishing them. We also discuss the impact of this distinction upon instrument validation and the design and analysis of summary subscales.

Background: Cancer patients may experience a decrease in cognitive functioning before, during and after cancer treatment. So far, the Quality of Life Group of the European Organisation for Research and Treatment of Cancer (EORTC QLG) developed an item bank to assess self-reported memory and attention within a single, cognitive functioning scale (CF) using computerized adaptive testing (EORTC CAT Core CF item bank). However, the distinction between different cognitive functions might be important to assess the patients' functional status appropriately and to determine treatment impact. To allow for such assessment, the aim of this study was to develop and psychometrically evaluate separate item banks for memory and attention based on the EORTC CAT Core CF item bank. Methods: In a multistep process including an expert-based content analysis, we assigned 44 items from the EORTC CAT Core CF item bank to the memory or attention domain. Then, we conducted psychometric analyses based on a sample used within the development of the EORTC CAT Core CF item bank. The sample consisted of 1030 cancer patients from Denmark, France, Poland, and the United Kingdom. We evaluated measurement properties of the newly developed item banks using confirmatory factor analysis (CFA) and item response theory model calibration. Results: Item assignment resulted in 31 memory and 13 attention items. Conducted CFAs suggested good fit to a 1-factor model for each domain and no violations of monotonicity or indications of differential item functioning. Evaluation of CATs for both memory and attention confirmed well-functioning item banks with increased power/reduced sample size requirements (for CATs ≥ 4 items and up to 40% reduction in sample size requirements in comparison to non-CAT format). Conclusion: Two well-functioning and psychometrically robust item banks for memory and attention were formed from the existing EORTC CAT Core CF item bank. These findings could support further research on self-reported cognitive functioning in cancer patients in clinical trials as well as for real-word-evidence. A more precise assessment of attention and memory deficits in cancer patients will strengthen the evidence on the effects of cancer treatment for different cancer entities, and therefore contribute to shared and informed clinical decision-making. [ABSTRACT FROM AUTHOR]

The article presents a response to the comment on comparing translations of the European Organization for Research in the Treatment of Cancer questionnaire-C30 using differential item functioning (DIF) analysis. The author responds to three intriguing issues. First of the issue is the proposal that DIF analysis might have been better to condition on scale scores derived from Item Response Theory scoring; second, the issue of the choices of reference group; and third, issues that confounding and effect modification are challenging DIF analyses.