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Item-Level Assessment of the Irritable Bowel Syndrome Quality of Life Questionnaire in Patients with Diarrheal Irritable Bowel Syndrome



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  • Personal Author:
  • Description:
    Background: In previous studies, the Irritable Bowel Syndrome Quality of Life (IBS-QOL) instrument has been determined to have good measurement properties for general irritable bowel syndrome (IBS) and the diarrheal IBS (IBS-d) subtype in clinical trials. Objective: This article aims to extend the true-score analyses that have been previously conducted to evaluate the IBS-QOL in IBS-d patients. Methods: Item response theory analysis was conducted by fitting models to responses from 753 patients with severe IBS-d from a recent clinical trial. Three item response theory models, the constrained graded response model (CGRM), the unconstrained GRM (UGRM), and the testlet response model (TRM), were fit to the 34 items of the IBS-QOL questionnaire. Subsequently, differential item functioning (DIF) for patient sex was assessed by fitting nested models by applying likelihood ratio tests. Model latent trait estimates were then compared with the IBS-QOL score and the IBS Symptom Severity Score. Results: Model fits improved with complexity, with the TRM model fitting best compared with the CGRM and UGRM. The DIF evaluation for patient sex flagged 17 items for the CGRM and 9 items for the UGRM; however, these items were not found to have much effect on the overall estimation of the latent trait. Differential testlet functioning was not indicated, and no items exhibited potential DIF under the TRM because likelihood ratio tests were not statistically significant. Comparison of latent trait estimates to the IBS Symptom Severity Score and IBS-QOL questionnaire revealed high Spearman correlations (0.47 and =0.99, respectively). Conclusion: Previous true-score approach results were supported by the IBS-QOL item-level analysis. Further, the IBS-QOL total score was found to be a valid measure of perceived quality of life for IBS-d patients when compared with more sophisticated model-based estimates of perceived quality of life. [Description provided by NIOSH]
  • Subjects:
  • Keywords:
  • ISSN:
    0149-2918
  • Document Type:
    Text
  • Funding:
    Grant
  • Genre:
    Journal Article
  • Place as Subject:
  • CIO:
    National Institute for Occupational Safety and Health (NIOSH)
  • Topic:
    Workplace Safety & Health
  • Location:
    North America
  • Volume:
    36
  • Issue:
    5
  • NIOSHTIC Number:
    nn:20055412
  • Citation:
    Clin Ther 2014 May; 36(5):663-679
  • Contact Point Address:
    David A. Andrae, PhD, Furiex Pharmaceuticals Inc, 3900 Paramount Pkwy, Suite 150, Morrisville, NC 27560
  • Email:
    david.andrae@furiex.com
  • Federal Fiscal Year:
    2014
  • Performing Organization:
    University of Washington
  • Peer Reviewed:
    True
  • Start Date:
    20050701
  • Source Full Name:
    Clinical Therapeutics
  • End Date:
    20250630
  • Collection(s):
  • Main Document Checksum:
    urn:sha-512:fc5b5ebb9712ea48884a54aba05cb02b64dcb49105827a2ec0305a223514d5ba2702b4a878d6a0ec685b1714b973504d52e251610a1e946f8929d87da4e1f4f9
  • Download URL:
  • File Type:
    Filetype[PDF - 1.88 MB ]
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