A Study of Antithrombin III Levels in Healthy Male and Female Subjects Tested Monthly for Eleven Months by Four Methods
Because of the increased interest in the role of Antithrombin III as a physiologic coagulation inhibitor and because of some previous problems we encountered in sequential measurement of this protein, the present study was designed to answer 3 questions: 1) Which of four methods (2 functional activity methods and 2 immunologic methods) is the most practical, accurate and reproducible? 2) Do normal subjects have relatively constant levels when tested sequentially by these methods? 3) What is the range of Antithrombin III levels in young healthy male and female subjects? A serum pool was tested by each of the 3 serum methods at least 20 different times throughout the study. The von Kaulla functional activity method gave the lowest standard deviation and coefficient of variation. In the group of 29 subjects this method proved to be the most practical and also gave very low coefficients of variation for individual subjects when they were tested from 11 to 16 times (range .023-.054). The other methods did not give such low coefficients of variation for individual subjects. The range of levels was 77 to 110% on 344 samples tested by the von Kaulla method With a mean of 92.8% and a standard deviation of 6.4%. The standard deviations for the pool and for individual subjects were greater but quite satisfactory for all methods.