STABILITY OF PROTEIN, ENZYME, AND NONPROTEIN CONSTITUENTS OF STORED FROZEN PLASMA

The present study was undertaken primarily to determine the stability of cer­ tain commonly analyzed constituents of frozen plasma over a 6-month period of storage. If stable, such plasma would have a number of practical uses in the clinical laboratory. Among these we include (1) the construction of quality control charts for maintaining precision of routine chemical methods, (2) the standardization of procedures, and (3) the determination of the statistical devia­ tion of each method. The employment of quality control charts in the laboratory has been illus­ trated by Levey and Jennings, 17 Henry and Segalove, 15 and Benenson and asso­ ciates. 3 Briefly this method consists of running daily determinations on aliquots of a large pooled source of material (plasma) and of subjecting a series of these daily determinations to statistical analysis. The average value and range of values are calculated. Thenceforth the daily aliquots serve as a sensitive indica­ tion of the precision and reliability of routine determinations. When the result on an aliquot falls outside the range, the test may be out of control. The use of quality control makes available a large volume of material (plasma) the chemical composition of which is precisely known, at least for a number of constituents. The use of such material in place of a "pure" standard has received some discussion. 1 • 15 • 17 Stable frozen plasma would also be a convenient substance with which to obtain and compare the standard deviations of chemical methods. Such information is helpful in evaluating a result as it applies to a single deter­ mination on an individual patient. The above factors hinge upon the chemical stability of frozen plasma. Infor­ mation is available regarding the stability of only a limited number of constitu­ ents of frozen plasma. 7 ' 12 ' "• 21