An interlaboratory evaluation of the IFCC method for aspartate aminotransferase with use of purified enzyme materials
Sampson, E.J.; Whitner, V.S.; Burtis, C.A.; McKneally, S.S.; Fast, D.M.; Bayse, D.D.
Clinical Chemistry 26(8): 1156-1164
1980
ISSN/ISBN: 0009-9147 PMID: 7389087 Document Number: 160572
The preparation and characterization of 4 materials and their uses in an interlaboratory evaluation of the proposed IFCC method for aspartate aminotransferase are described. The cytoplasmic isoenzyme of aspartate aminotransferase was purified from human erythrocytes to a high specific activity (230 kU). Each of 16 laboratories measured duplicate specimens from the 4 pools on 3 days. (Techniques and equipment they used are described.) The among-laboratory variance component was consistently greater than either the within-day within-laboratory or the among-day within-laboratory variance components. Estimates of among-laboratory performance were not improved by treating individual laboratory data in 3 different ways; by not subtracting blank measurements; by subtracting specimen matrix blank; or by excluding 5 laboratories with the worst within-laboratory performances. Possible inadequacies of the proposed method are described.