Analysis of Overlapping Symptoms in Co-Occurring Conditions
*Douglas Gunzler, Case Western Reserve University
Keywords: structural equation modeling, factor analysis, multiple indicator multiple cause model, differential item functioning, measurement invariance, patient reported outcomes
Symptoms or test findings may be common to two or more conditions. As a result of such overlap, diagnoses, treatment decisions, and inferences about the effectiveness of treatments for these conditions can be biased. Structural equation modeling methods provide flexibility in handling this type of differential item functioning and disentangling the overlap. Scales and scoring approaches can be revised to be free of this overlap, leading to better care. We discuss an example of depression screening in multiple sclerosis patients in which depressive symptoms overlap with other symptoms, such as fatigue, cognitive impairment, and physical impairment.