Positive Health Online

Abstract

VICKERS, Integrative Medicine Service, Memorial Sloane-Kettering Cancer Center, New York, New York 10021, USA, vickersa@mskcc.org, shows how to reduce the number of patients needed for randomized trials.

Background

In a typical trial, patients are assessed for symptom severity at baseline, randomized to treatment or control and reassessed after a suitable follow-up period.

Methodology

Medical statistics.

Results

It can be shown that when patients with chronic conditions are used, as is often the case with complementary therapies, the sample size can be reduced by two ways: repeat measurement and analysis of co-variance (ANCOVA). An example is given of a trial of acupuncture for back pain. Administering a pain questionnaire twice at baseline and four times at follow-up reduces the number of patients required by about 20%. A further 10% reduction is obtained by the use of ANCOVA.

Conclusion

It is desirable to reduce the number of patients required for a randomized controlled trial by a third; however ANCOVA is complex and expert statistical help is needed.

References

Vickers A. How to reduce the number of patients needed for randomized trials: a basic introduction. Complementary Therapies in Medicine 9 (4): 234-236, Dec 2001.