INTEROBSERVER REPRODUCIBILITY AND BIOLOGICAL VARIABILITY OF THE SURGICUTT-II BLEEDING-TIME

The bleeding time is a readily and easily performed clinical test with immediate results, but there is a degree of subjectivity in its perfo rmance and interpretation. We performed a study on 27 volunteers desig ned to determine the normal range, interobserver reproducibility, and biological variability of the test. Bleeding times in these normal sub jects ranged from as low as 129 seconds to as high as 803 seconds. The interobserver variability was 106 seconds (2 standard deviations of t he mean of the differences of paired results of repeated measurements) , and the coefficient of variation was 18%. For bleeding times taken o n the same subjects 6 weeks apart, when the same nurse performed the t est at both visits, the difference was 150 seconds (2 standard deviati ons of the mean of the differences of paired samples) and the coeffici ent of variation was 27%, and they were essentially the same if a diff erent nurse performed the tests at each visit. There is a wide range i n the bleeding times among subjects. However, within individuals there is little biological variability, and most of the difference over tim e is due to interobserver variability This suggests that changes in bl eeding time are clinically useful in predicting platelet responsivenes s in individual patients.