A clinician-administered severity rating scale for illness anxiety: development, reliability, and validity of the H-YBOCS-M.

Background: Clinician-administered measures to assess severity of illness anxiety and response to treatment are few. The authors evaluated a modified version of the hypochondriasis-Y-BOCS (H-YBOCS-M), a 19-item, semistructured, clinician-administered instrument designed to rate severity of illness-related thoughts, behaviors, and avoidance.

Methods: The scale was administered to 195 treatment-seeking adults with DSM-IV hypochondriasis. Test-retest reliability was assessed in a subsample of 20 patients. Interrater reliability was assessed by 27 interviews independently rated by four raters. Sensitivity to change was evaluated in a subsample of 149 patients. Convergent and discriminant validity was examined by comparing H-YBOCS-M scores to other measures administered. Item clustering was examined with confirmatory and exploratory factor analyses.

Results: The H-YBOCS-M demonstrated good internal consistency, interrater and test-retest reliability, and sensitivity to symptom change with treatment. Construct validity was supported by significant higher correlations with scores on other measures of hypochondriasis than with nonhypochondriacal measures. Improvement over time in response to treatment correlated with improvement both on measures of hypochondriasis and on measures of somatization, depression, anxiety, and functional status. Confirmatory factor analysis did not show adequate fit for a three-factor model. Exploratory factor analysis revealed a five-factor solution with the first two factors consistent with the separation of the H-YBOCS-M items into the subscales of illness-related avoidance and compulsions.

Conclusions: H-YBOCS-M appears to be valid, reliable, and appropriate as an outcome measure for treatment studies of illness anxiety. Study results highlight "avoidance" as a key feature of illness anxiety-with potentially important nosologic and treatment implications.