RESUMEN
OBJECTIVE: To develop and validate parallel short forms for the assessment of general anxiety in cardiovascular rehabilitation patients, that facilitate repeated measurement over time without contamination from residual practice effect variance. DESIGN: Development of the parallel short forms using Rasch analysis. Validation study. SETTING: Cardiac rehabilitation centres in Germany. SUBJECTS: Cardiovascular rehabilitation patients. INTERVENTIONS: Not applicable. MAIN MEASURES: Parallel short forms PaSA-cardio, Hospital Anxiety and Depression Scale, Short Form Health Survey SF-12 and Structured Clinical Interview for DSM-IV Axis I Disorders. RESULTS: Each version of the parallel short forms (PaSA-cardio-I and PaSA-cardio-II) comprises ten items. The two forms fitted to the Rasch model with a non-significant item-trait interaction (PaSA-cardio-I: chi-square = 39.49, degrees of freedom = 30, probability = 0.12; PaSA-cardio-II: chi-square = 26.56, degrees of freedom = 30, probability = 0.65). Person-separation reliability was 0.75/0.76. Unidimensionality could be verified. Correlation between the two models was 0.94 and 0.95, and correlations with the underlying item bank were 0.95 and 0.93. Validity could be confirmed. The area under the curve was between 0.88 and 0.97 for PaSA-cardio-I and between 0.92 and 0.95 for PaSA-cardio-II. CONCLUSIONS: Assessment of general anxiety in cardiovascular rehabilitation patients with the PaSA-cardio was valid, economical and accurate. The two forms of the PaSA-cardio are equivalent and allow retest without contamination from residual practice effect variance.