Validity of overall self-rated health as an outcome measure in small samples: a pilot study involving a case series James E. Rohrer PhD, 1 David C. Herman MD, 2 Stephen P. Merry MD MPH, 3 James M. Naessens ScD 4 and Margaret S. Houston, MD MPH 5 1 Professor, Department of Family Medicine, Mayo Clinic-Rochester, Rochester, MN, USA 2 Consultant, Department of Employee and Community Health, Mayo Clinic-Rochester, Rochester, MN, USA 3 Consultant, Department of Family Medicine, Mayo Clinic-Rochester, Rochester, MN, USA 4 Research Consultant, Division of Health Care Policy & Research, Mayo Clinic, Rochester, MN, USA 5 Consultant, Department of Family Medicine, Mayo Clinic-Rochester, Rochester, MN, USA Keywords evaluation methods, lifestyle coaching, motivational interviewing, obesity counseling, self-rated health, weight loss Correspondence James Rohrer Mayo Clinic-Rochester Department of Family Medicine 200 First St SW Rochester MN 55905 USA E-mail: rohrer.james@mayo.edu Accepted for publication: 25 February 2008 doi:10.1111/j.1365-2753.2008.01017.x Abstract Objective A single-item measure of overall self-rated health (SRH) commonly is used in population surveys, but has not been used in small pilot projects. The purpose of this study was to assess the validity of SRH in small samples. Design We used data from a prospective, observational weight-loss project to compare change in SRH with change in body weight and physical activity (PA) (minutes) over 30 days (n = 34). Body mass index at baseline ranged from 25.5 to 50.4 (mean = 36.1, median = 34.6). SRH was self-assessed using the following question: How would you rate your health overall? Results An increase in weight was associated with a reduction in SRH (r = 0.37, P = 0.03). An increase in PA was associated with improved SRH (r = 0.39, P = 0.02). Conclusions A single-item SRH measure may be an efficient method for measuring programme outcomes, and may also be useful for comparing the relative effectiveness of different programmes in pilot projects and quality improvement studies. Introduction Overall subjective health is an important outcome, from the patient’s point of view. It also is a valid summary measure for overall health status. A single-item measure of overall self-rated health (SRH) commonly is used in both cross-sectional and pro- spective population surveys [1–9]. Less commonly, it has been used in surveys of clinic populations [10–12]. In randomized clini- cal trials, much longer instruments are used to measure health- related quality of life; the single item is not used in these studies or in small pilot projects or quality improvement projects. Investigators undertaking small projects often operate on limited budgets, and thus, the single-item measure could be very convenient for them. Quality improvement projects face the addi- tional requirement of disrupting practice as little as possible so that investigators can be optimistic that successful innovations will remain effective when translated into in general use. Furthermore, if the single-item measure of overall health is sufficiently sensitive for use in small studies, then it could serve as a common yardstick for comparisons across studies targeting different clinical issues. The purpose of this study was to assess the validity of a single- item measure of overall SRH in a small prospective weight-loss project by comparing change in SRH with change in body weight. If short-term reductions in body weight are associated with sig- nificant improvements in SRH, then the validity of the measure is supported, and SRH might be useful in a variety of small clinic projects. Methods Forty-two patients were enrolled in a weight-loss project between April 18 and October 30 of 2007. Information was obtained in an initial motivational interview and 30 days later. Two patients omitted assessment of SRH at baseline, and so were dropped from this analysis. Six were lost to follow-up. A case series of 34 patients remained for analysis. Body mass index at baseline ranged from 25.5 to 50.36 (mean = 36.1, median = 34.6). The study was approved by the Institutional Review Board in the Mayo Clinic-Rochester. Journal of Evaluation in Clinical Practice ISSN 1356-1294 © 2009 The Authors. Journal compilation © 2009 Blackwell Publishing Ltd, Journal of Evaluation in Clinical Practice 15 (2009) 366–369 366