Objective: To compare the reliability, validity and change in patient clinical status over time with treatment for six potential outcome questionnaires in a defined population of patients.
Setting: Physician based, multidoctor teaching practice.
Patients: Three hundred thirty-five consecutive patients presenting with new complaints were solicited. One hundred eighty-six agreed to participate.
Interventions: The six questionnaires being studied were administered to each of the participants on three separate occasions. They were: a) prior to clinical evaluation for their chief complaint, b) immediately after clinical evaluation and before treatment and c) 6 wk later.
Measurements: Each instrument was scored following the prescribed methods of interpretation from the original literature describing it. Results were submitted for analysis by Pearson correlation and two-way analysis of variance as appropriate.
Main results: Differences were found in the mean value of the modified Zung with respect to both gender and time. An unexpected drop in patients' somatic perceptions in association with the process of clinical evaluation was found for the Modified Somatic Pain Questionnaire. Overall, the Oswestry and Visual Analogue Pain Scale were the most reliable and responsive to clinical change for musculoskeletal disorders.
Conclusions: This investigation demonstrated substantial differences in the validity and reliability of commonly referenced self-administered instruments for quantifying patient perceptions of pain and disability. The Oswestry and Visual Analogue Pain Scale were both more reliable and valid than other instruments.