Thymol turbidity and thymol flocculation tests as a screening technic to detect blood donors carrying the hepatitis virus. I. The results of screening 52,662 consecutive blood donors

Abstract

The thymol turbidity test was done by the Shank‐Hoagland (pH 7.55) method and flocculation tests were done on all lipemic serum over 5.0 T.T. units. The mean for the readings on clear (nonlipemic) sera (87%) was 3.8 units, and the standard deviation 2.1. The screening level of abnormality at the 95% confidence level was 8.0 T.T. units in clear sera (or 8.0 T.T. units with positive flocculation in lipema sera), and 10.1 T.T. units (also with T.F. in lipemic sera) at the 99% confidence level. There were 5.4% and 1.7% “abnormal” bloods, respectively. The values for all sera, including lipemic, were: mean 4.4, S.D. 2.7, or 9.9 T.T. units at the 95% confidence level and 12.5 at 99%. A parallel study of the use of inactivated sera for the T.T. test is discussed. It lowered the T.T. values an average of 3.7 units but producd a more abnormal distribution of test results. Since the donors were healthy adults representing a good cross section of the adult population and the levels of abnormality (95 and 99% confidence) found for the test were considerably higher than that reported by most authors, the validity of the use of lower levels to screen blood donors is questioned. The use of large numbers of acceptable blood donors may be a better way to establish normal and abnormal values for clinical laboratory tests. The incidence of hepatitis in transfused patients, followed for six months, is reported in Part II.