We performed IRT by low versus high CKD stage, diabetes versus no diabetes and high (>3 diagnoses) versus low medical comorbidity burden.
IRT models of each rating scale were affected in a limited way by CKD stage, diabetes and medical comorbidity burden. Sleep disturbances on the QIDS-SR16 were more discriminatory for depression in diabetics and those with high comorbidity burden. Pessimism and guilt from the BDI compared to QIDS-SR16 were more discriminatory of depression in the high CKD and high comorbidity groups, respectively.
Overall item differences were modest, and chronic disease severity by CKD stage, diabetes mellitus or other medical comorbidities did not appreciably contribute to differences in scale performance.