Andrae David A, Covington Paul S, Patrick Donald L
Furiex Pharmaceuticals Inc, Morrisville, North Carolina.
Furiex Pharmaceuticals Inc, Morrisville, North Carolina.
Clin Ther. 2014 May;36(5):663-79. doi: 10.1016/j.clinthera.2014.04.009. Epub 2014 May 9.
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.
This article aims to extend the true-score analyses that have been previously conducted to evaluate the IBS-QOL in IBS-d patients.
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.
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).
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. ClinicalTrials.gov identifier: NCT01130272.
在以往的研究中，肠易激综合征生活质量（IBS-QOL）工具已被确定在临床试验中对一般肠易激综合征（IBS）和腹泻型IBS（IBS-d）亚型具有良好的测量属性。
本文旨在扩展先前进行的真实分数分析，以评估IBS-d患者的IBS-QOL。
通过将模型拟合到最近一项临床试验中753例重度IBS-d患者的反应，进行项目反应理论分析。将三个项目反应理论模型，即约束等级反应模型（CGRM）、无约束GRM（UGRM）和测验组反应模型（TRM），拟合到IBS-QOL问卷的34个项目上。随后，通过应用似然比检验拟合嵌套模型，评估患者性别的项目功能差异（DIF）。然后将模型潜在特质估计值与IBS-QOL得分和IBS症状严重程度得分进行比较。
模型拟合随着复杂性的增加而改善，与CGRM和UGRM相比，TRM模型拟合最佳。对患者性别的DIF评估为CGRM标记了17个项目，为UGRM标记了9个项目；然而，这些项目对潜在特质的总体估计没有太大影响。未显示测验组功能差异，并且在TRM下没有项目表现出潜在的DIF，因为似然比检验在统计学上不显著。潜在特质估计值与IBS症状严重程度得分和IBS-QOL问卷的比较显示出高Spearman相关性（分别为0.47和≥0.99）。
IBS-QOL项目水平分析支持了先前的真实分数方法结果。此外，与基于更复杂模型的生活质量感知估计相比，IBS-QOL总分被发现是IBS-d患者生活质量感知的有效测量指标。ClinicalTrials.gov标识符：NCT01130272。
