Criterion contamination of depression scales in patients with rheumatoid arthritis: the need for interpretation of patient questionnaires (as all clinical measures) in the context of all information about the patient.

The validity of information on a patient questionnaire may not necessarily be generalizable to all individuals and situations, and may depend on the context in which a person provides the information. Examples may be seen in responses of people with rheumatoid arthritis on the Minnesota Multiphasic Personality Inventory (MMPI), on the original Beck Depression Inventory (BDI), and on the Centers for Epidemiologic Studies Depression Scale (CES-D). Several reports have indicated tendencies toward hypochondriasis, depression, and/or hysteria on the MMPI, and tendencies toward depression on the original BDI and CES-D. However, these interpretations were based in large part on responses to such statements as "I am in just as good physical health as most of my friends," "I can work about as well as before," and "I could not get going." These responses would suggest psychological concerns in people who have no somatic disease, the type of subjects in whom these scales were validated, but would also appear appropriate for people with rheumatoid arthritis, including those with no psychological problems. Rheumatologists confirmed independently the likelihood that people with rheumatoid arthritis would respond differently from the general population in responding to these and other statements. This phenomenon, known as criterion contamination, would explain much, but not all, of elevations in scores on these scales in patients with rheumatoid arthritis. The BDI was revised in 1996, as the Beck Depression Inventory-II (BDI-II), to eliminate the items reflecting somatic disease.