Analysis on items of general module of quality of life instrument for chronic diseases by item response theory

ObjectiveTo analyze items of the general module of the quality of life instrument for chronic diseases (QLICD-GM)for selection of items with more information using item response theory(IRT).MethodsA total of 602 inpatients with one of the 7 different chronic diseases were measured by QLICD-GM.With MULTILOG,Samejima's Graded Response Model was used to calculate parameters of discrimination and difficulty,information function,and to get item characteristic curve.ResultsAmong the 29 items,the discrimination parameters of all items were between 1.2-1.9 and the difficulty parameters of each item increased monotonically for all items with a range from -3.05 to 2.18.Twenty-four items were selected as good ones by average information and item characteristics.ConclusionEach item of the QLICD-GM has good discrimination,suitable item choice and moderate difficulty.The item analysis based on item response theory can select good items with more information and refined characteristics to overcome weakness of classical test theory