Measuring health status in older patients. The SF-36 in practice.

OBJECTIVE To examine the use of the Medical Outcomes Study short form 36-item (SF-36) health status measure in older patients receiving health care; to explore the influence of age and physical and cognitive status on response to and completion of the SF-36 questionnaire. DESIGN Prospective observational study. SETTINGS Hospital and ambulatory patients aged 65 years and over in the medical and surgical wards and outpatient department of a teaching hospital and a local general practitioner's surgery. SUBJECTS 1014 hospital inpatients, 80 hospital outpatients and 40 patients attending their general practitioner's surgery. MAIN OUTCOME MEASURES Response rates, overall rates of completion (sufficient to calculate a valid SF-36 score) and completion of individual questions. RESULTS 37 out of 40 ambulatory patients in general practice (93%) and 71 out of 80 outpatients (89%) returned a self-completed questionnaire. In hospital inpatients the overall response rate was only 46% (369 of 802). This was improved by interview administration to 77.4% (164 of 212). Logistic regression analysis revealed that self-completion, cognitive dysfunction, disability and age were all independently associated with poor overall response rates. Among those patients who returned a completed questionnaire, completion of individual questions sufficient to calculate a valid score was variable. Only 62.5% of inpatients who self-completed a questionnaire gave sufficient response to calculate a score on the mental health subscale, compared with 93.7% of general practice patients. CONCLUSION The self-administered questionnaire is unacceptable for older hospital inpatients. Use of an interviewer improves response, but factors which influence health status, such as physical and cognitive dysfunction, have a significant effect on response rates. Therefore the utility of the SF-36 in its present form as a routine health status measure for use in older hospital inpatients is questioned.