Analysis of variability in lymphocyte transformation tests.

To estimate the importance of a number of variables influencing the results of the lymphocyte transformation test (LTT), we analysed retrospectively the results of 250 LTTs on healthy control lymphocytes tested during the last 5 years as part of the routine LTT program. Prospectively, frozen cells from 3 donors were tested together on 5 different occasions. Differences in day-to-day test conditions had only minor influence. The influence of biologic variables was also negligible. The 2 most important factors were intrinsic cell differences, most probably due to damage during freezing, and genetic influences. To demonstrate minor differences between donors or between bleeding dates, repeated testing is necessary to eliminate these intrinsic variables and to allow statistical analysis.