Using the rasch model to validate and enhance the interpretation of the functional assessment of cancer therapy-kidney symptom index - Disease-related symptoms scale Journal Article


Authors: Luo, X.; Cappelleri, J. C.; Cella, D.; Li, J. Z.; Charbonneau, C.; Kim, S. T.; Chen, I.; Motzer, R. J.
Article Title: Using the rasch model to validate and enhance the interpretation of the functional assessment of cancer therapy-kidney symptom index - Disease-related symptoms scale
Abstract: Objectives: The Functional Assessment of Cancer Therapy-Kidney Symptom Index - Disease-Related Symptoms (FKSI-DRS) was developed to assess patients' kidney-cancer-related symptoms. The Rasch rating scale, a one-parameter logistic item response model, may enhance FKSI-DRS interpretation and validate its measurement properties. Methods: We applied the Rasch model to FKSI-DRS data from a randomized phase 3 trial in which first-line sunitinib therapy showed superiority to interferon-alfa in patients with metastatic renal cell carcinoma. Of 750 enrolled patients, 668 patients completed the questionnaire on cycle 1, day 28 and were evaluated in the current study. The nine FKSI-DRS items were analyzed to enhance interpretation of the summary score by using an item characteristic curve that related score to probability of reporting specific symptoms. Results: The Rasch model fitted the FKSI-DRS well: 8 of 9 items had acceptable infit and outfit statistics (<1.5, >0.5); item difficulty spanned a wide range (-3.23 to 1.64 logits); and the five response categories performed adequately. The item characteristic curve offered enhanced interpretation of FKSI-DRS: For example, an FKSI-DRS score of 27 (mean baseline score for total sample) indicated a 47% chance of reporting "no" to "lack of energy," although a two-point difference between sunitinib and interferon-alfa, averaged across all assessments (29 vs. 27), corresponded to sunitinib achieving a 28% increase (13% absolute difference) in the probability of reporting "no" to "lack of energy" (60% vs. 47%). Conclusions: Data suggest that the FKSI-DRS is an adequate measure of symptom status in patients with metastatic renal cell carcinoma. The Rasch model supports its validation and enhances its interpretation. © 2008, International Society for Pharmacoeconomics and Outcomes Research (ISPOR).
Keywords: adult; controlled study; aged; major clinical study; clinical trial; sunitinib; validation process; alpha interferon; controlled clinical trial; randomized controlled trial; validation study; cancer therapy; kidney carcinoma; questionnaire; statistical analysis; multicenter study; rating scale; phase 3 clinical trial; statistical model; fksi-drs; mrcc; rasch model; symptom status; functional assessment of cancer therapy kidney symptom index disease related symptoms scale; rasch analysis
Journal Title: Value in Health
Volume: 12
Issue: 4
ISSN: 1098-3015
Publisher: Elsevier Science, Inc.  
Date Published: 2009-06-01
Start Page: 580
End Page: 586
Language: English
DOI: 10.1111/j.1524-4733.2008.00473.x
PROVIDER: scopus
PUBMED: 19900256
DOI/URL:
Notes: --- - "Export Date: 30 November 2010" - "CODEN: VIHLF" - "Source: Scopus"
Altmetric
Citation Impact
MSK Authors
  1. Robert Motzer
    950 Motzer