Differential item functioning impact in a modified version of the Roland–Morris Disability Questionnaire
ABSTRACT To evaluate a modified version of the Roland-Morris Disability Questionnaire for differential item functioning (DIF) related to several covariates.
DIF occurs in an item when, after controlling for the underlying trait measured by the test, the probability of endorsing the item varies across groups.
Secondary data analysis of two studies of participants with back pain (total n = 875). We used a hybrid item response theory/ logistic regression approach for detecting DIF. We obtained scores that accounted for DIF. We evaluated the impact of DIF on individual and group scores, and compared scores that ignored or accounted for DIF in terms of the strength of association with SF-36 subscale scores.
DIF was found in 18/23 items. Salient scale-level differential functioning was found related to age, education, and employment. Overall 24 participants (3%) had salient scale-level differential functioning. Mean scores across demographic groups differed minimally when accounting for DIF. The strength of association of scores with SF-36 scores was similar for scores that ignored and scores that accounted for DIF.
The modified version of the Roland-Morris Disability Questionnaire appears to have largely negligible DIF related to the covariates assessed here.
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ABSTRACT: To evaluate psychometric properties of a widely used patient experience survey. English-language responses to the Clinician & Group Consumer Assessment of Healthcare Providers and Systems (CG-CAHPS®) survey (n = 12,244) from a 2008 quality improvement initiative involving eight southern California medical groups. We used an iterative hybrid ordinal logistic regression/item response theory differential item functioning (DIF) algorithm to identify items with DIF related to patient sociodemographic characteristics, duration of the physician-patient relationship, number of physician visits, and self-rated physical and mental health. We accounted for all sources of DIF and determined its cumulative impact. The upper end of the CG-CAHPS® performance range is measured with low precision. With sensitive settings, some items were found to have DIF. However, overall DIF impact was negligible, as 0.14 percent of participants had salient DIF impact. Latinos who spoke predominantly English at home had the highest prevalence of salient DIF impact at 0.26 percent. The CG-CAHPS® functions similarly across commercially insured respondents from diverse backgrounds. Consequently, previously documented racial and ethnic group differences likely reflect true differences rather than measurement bias. The impact of low precision at the upper end of the scale should be clarified.Health Services Research 12/2011; 46(6pt1):1778-802. DOI:10.1111/j.1475-6773.2011.01299.x · 2.49 Impact Factor
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ABSTRACT: A post hoc simulation of a computer adaptive administration of the items of a modified version of the Roland-Morris Disability Questionnaire. To evaluate the effectiveness of adaptive administration of back pain-related disability items compared with a fixed 11-item short form. Short form versions of the Roland-Morris Disability Questionnaire have been developed. An alternative to paper-and-pencil short forms is to administer items adaptively so that items are presented based on a person's responses to previous items. Theoretically, this allows precise estimation of back pain disability with administration of only a few items. Data were gathered from 2 previously conducted studies of persons with back pain. An item response theory model was used to calibrate scores based on all items, items of a paper-and-pencil short form, and several computer adaptive tests (CATs). Correlations between each CAT condition and scores based on a 23-item version of the Roland-Morris Disability Questionnaire ranged from 0.93 to 0.98. Compared with an 11-item short form, an 11-item CAT produced scores that were significantly more highly correlated with scores based on the 23-item scale. CATs with even fewer items also produced scores that were highly correlated with scores based on all items. For example, scores from a 5-item CAT had a correlation of 0.93 with full scale scores. Seven- and 9-item CATs correlated at 0.95 and 0.97, respectively. A CAT with a standard-error-based stopping rule produced scores that correlated at 0.95 with full scale scores. A CAT-based back pain-related disability measure may be a valuable tool for use in clinical and research contexts. Use of CAT for other common measures in back pain research, such as other functional scales or measures of psychological distress, may offer similar advantages.Spine 06/2008; 33(12):1378-83. DOI:10.1097/BRS.0b013e3181732acb · 2.45 Impact Factor
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ABSTRACT: Outcome assessment normally used in research can support the therapeutic process by tracking patient symptoms and function and offering a common language to clinicians and researchers. This study's objectives were to (1) identify patient-based outcomes assessments used in published chiropractic studies, (2) describe a framework for identifying appropriate sets of measures, and (3) address the challenges associated with these measures relevant to chiropractic. This literature review identified and evaluated the most commonly used to outcome measures in chiropractic research. Instruments were evaluated in terms of feasibility, practicality, economy, reliability, validity, and responsiveness to clinical change. A search of PubMed and Index to Chiropractic Literature (from inception to June 2006) was performed. A total of 1166 citations were identified. Of these, 629 were selected as relevant. The most common patient-based outcomes assessments instruments identified were the Oswestry Pain/Disability Index, Visual Analog Scale, and Short Form 36. The integration of outcome measures is consistent with current national initiatives to enhance health care quality through performance measurement and can also be used to further the field of chiropractic health care research. Outcome measures are both a research tool and a means by which providers can consistently measure health care quality. Based upon this review, there is a wide range of outcome measures available for use in chiropractic care. Those most commonly cited in the literature are the numeric rating scale, Visual Analog Scale, Oswestry Pain/Disability Index, Roland-Morris Low Back Pain and Disability Questionnaire, and Short Form 36.Journal of manipulative and physiological therapeutics 07/2008; 31(5):355-75. DOI:10.1016/j.jmpt.2008.04.007 · 1.25 Impact Factor