PIH66 - Development Of A Medication-Problem Coping Scale (Mpcs) And Items Calibration Using One-Parameter Logistic (1pl) And Two-Parameter Logistic (2pl) Models

Abstract

Adverse drug problems (ADPs) have caused significant morbidity and mortality to patients. The objective of this study was to develop a medication-problem coping scale (MPCS) to measure patients’ coping responses to their ADP and calibrate the developed items using one-parameter logistic (1PL) and two-parameter logistic (2PL) models. A comprehensive literature review was conducted to identify candidate items to measure patient’s coping strategies when dealing with perceived ADPs. Supplementary items were then added to fill in the content gaps. The items were administered to patients in the community pharmacies which are incorporated into the Minnesota practice-based research network (PBRN). After collecting data from 140 patients, eleven items which met the assumptions of item response theory were calibrated using the 1PL and 2PL models respectively to determine which model is favored. The 1PL and 2PL model were compared by taking goodness-of-fit statistics, reliability of the estimated person scores, and standard error of measurement (SEM) into account. First, the chi-squared difference test was highly significant (X2(41.61, 10), P<0.0001) indicating that the 2PL model provided a better fit to the item responses compared to the 1PL model. This result was supported by the information-theoretic fit index (AIC) and the RMSEA value, all of which favored the 2PL model. In addition, the 2PL model was preferred with a higher value of score reliability estimate (0.82) compared to that of the 1PL model (0.79). Finally, the 2PL model had much more information and much lower SEM over most of the coping behavior range. Our findings indicated that the 2PL model was preferred than the 1PL model. It suggests that the 2PL model be used to obtain item parameters and to assess information function.