The factor structure of the Revised Illness Perception Questionnaire (IPQ-R) in end-stage renal disease patients.
ABSTRACT The purpose of this study was to examine the factor structure of the Revised Illness Perceptions Questionnaire (IPQ-R) in a sample of 374 end-stage renal disease (ESRD) patients. A confirmatory factor analysis of the IPQ-R, including the illness identity subscale, demonstrated adequate model fit for the factor structure as originally defined by (Moss-Morris, R., Weinman, J., Petrie, K. J., Horne, R., Cameron, L. D., & Buick, D. (2002). The revised Illness Perception Questionnaire (IPQ-R). Psychology & Health, 17 (1), 1-16.) Modifying the a-priori IPQ-R factor structure by removing two items with low factor loadings and specifying a path between personal control and item 23 had marginally better fit. A separate exploratory factor analysis of the causal items indicated three factors relating to Biological, Psychological and Behavioural causes. These findings provide evidence towards the validity and reliability of the IPQ-R as a suitable measure of illness perceptions in the context of ESRD.
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ABSTRACT: To provide new insights into the psychometrics of the revised Illness Perception Questionnaire (IPQ-R) in cancer patients. To undertake, for the first time using data from breast, colorectal and prostate cancer patients, a confirmatory factor analysis (CFA) to assess the validity of the IPQ-R's core seven-factor structure. Also, for the first time in any illness group, to undertake Rasch analysis to explore the extent to which the IPQ-R factors form unidimensional scales, with linear measurement properties and no Differential Item Functioning (DIF). Patients with potentially curable breast, colorectal or prostate cancer, within 6months post-diagnosis, completed the IPQ-R online (N=531). CFA was conducted, including multi-sample analysis, and for each IPQ-R factor fit to the Rasch model was assessed by examining, amongst other things, item fit, DIF and unidimensionality. The CFA showed a moderate fit of the data to the IPQ-R model, and stability across diagnosis, although fit was significantly improved following the removal of selected items. All seven factors achieved fit to the Rasch model, and exhibited unidimensionality and minimal DIF, although in most cases this was after some item rescoring and/or deletion. In both analyses, IPQ-R items 12, 18 and 24 were indicated as misfitting and removed. Given the rigorous standard of Rasch measurement, and the generic nature of the IPQ-R, it stood up well to the demands of the Rasch model in this study. Importantly, the results show that with some relatively minor, pragmatic modifications the IPQ-R could possess Rasch-standard measurement in cancer patients.Journal of psychosomatic research 12/2013; 75(6):556-62. · 2.91 Impact Factor
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ABSTRACT: Concerns are present on the limited value of renal function alone in defining the optimal moment to start dialysis. Disease-related symptoms and health-related quality of life (HRQOL) may have additional clinical value in defining this moment, but little is known about how these parameters change during pre-dialysis care. The aims of our study were to describe the course of symptoms and HRQOL during pre-dialysis care and to investigate their association with poor health outcomes. In the prospective PREPARE-2 cohort, incident patients starting specialized pre-dialysis care were included when referred to one of the 25 participating Dutch outpatient clinics (2004-2011). In the present analysis, 436 patients with data available on symptoms and HRQOL were included. Clinical data, symptoms (revised illness perception questionnaire), and HRQOL (short form-36 questionnaire; physical and mental summary score) were collected every 6-month interval. A time-dependent Cox proportional hazard model was used to associate symptoms and HRQOL with the combined poor health outcome (i.e. starting dialysis, receiving a kidney transplant, and death). All symptoms increased, especially fatigue and loss of strength, and both the physical and mental summary score decreased over time, with the most pronounced change during the last 6-12 months of follow-up. Furthermore, each additional symptom (adjusted HR 1.04 (95% CI, 1.00-1.09)) and each 3-point lower physical and mental summary score (adjusted HR 1.04 (1.02-1.06) and 1.04 (1.02-1.06) respectively) were associated with a higher risk of reaching the combined poor health outcome within the subsequent 6 months. The number of symptoms increased and both the physical and mental HRQOL score decreased during pre-dialysis care and these changes were associated with starting dialysis, receiving a kidney transplant, and death. These results may indicate that symptoms and HRQOL are good markers for the medical condition and disease stage of pre-dialysis patients.PLoS ONE 01/2014; 9(4):e93069. · 3.53 Impact Factor
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ABSTRACT: BACKGROUND: The Revised Illness Perception Questionnaire (IPQ-R) has been used extensively in the study of illness perceptions across different populations. Only few confirmatory factor analytic (CFA) studies of the questionnaire are available. This study examines the construct and discriminant validity of the Turkish IPQ-R in patients with diabetes and cardiovascular disease focusing on the hypothesized seven dimensions of personal controllability, treatment controllability, timeline acute/chronic, timeline cyclical, coherence, consequences and emotional representations. METHODS: 302 patients (60.6% women) with a medically confirmed diagnosis of diabetes or cardiovascular disease and a mean age of 53.9 years were recruited from out-patient clinics in Turkey and surveyed by means of standardized interviews. Direct maximum likelihood confirmatory factor analysis was conducted. RESULTS: Several areas of ill-fit were identified in the original measurement model of the IPQ-R. Four items (items 17, 19, 20, and 31) were deleted because of poor factor loadings. Also, two error covariances (between items 33 and 34 and between items 7 and 8) were added and item 6 respecified to obtain a good model fit. The modified 34-item model showed good reliability and discriminant validity. CONCLUSION: In accordance with studies on other language adaptations of the questionnaire, we identified certain items of the IPQ-R as potential sources of poor model fit. Their inclusion should be reconsidered in future applications of the questionnaire and researchers should examine whether our reduced set of items is stable across different populations. Our modified 34-item model showed a good reliability and discriminant validity and hence could be a valuable instrument in the assessment of illness perceptions in the Turkish health care setting, provided that the model is confirmed in subsequent research.BMC Public Health 10/2012; 12(1):852. · 2.08 Impact Factor