Clinical Interpretation of Plasma Glucose Values

Abstract

The use of plasma instead of whole blood for glucose determinations has become increasingly frequent. Since the values obtained differ significantly, it is necessary to establish new standards for the interpretation of plasma glucose levels. Both whole blood and plasma glucose concentrations were determined simultaneously on 480 blood samples from 120 glucose tolerance tests. From these determinations, a mathematical formula for the interconversion of plasma and whole blood glucose values was established: Whole blood glucose equals .0925 + .8543 plasma glucose. From this formula, normal upper limits were derived for the interpretation of the oral glucose tolerance test using plasma glucose values: 185 mg per 100 ml at one hour and 140 mg per 100 ml at two hours. Applying these levels, interpretations from simultaneous plasma and whole blood glucose values of the 120 glucose tolerance tests were compared and the results agreed well.