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The long‐term within‐ and between‐laboratory variability for assay of antithrombin, and proteins C and S: results derived from the external quality assessment program for thrombophilia screening of the ECAT Foundation
Author(s) -
Meijer P.,
Kluft C.,
Haverkate F.,
De Maat M. P. M.
Publication year - 2003
Publication title -
journal of thrombosis and haemostasis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.947
H-Index - 178
eISSN - 1538-7836
pISSN - 1538-7933
DOI - 10.1046/j.1538-7836.2003.00141.x
Subject(s) - antithrombin , analyte , protein s , reference range , medicine , bradford protein assay , chemistry , protein c , chromatography , heparin
Summary. A stable laboratory performance is important for comparability and transferability of laboratory data both within and between laboratories. The lack of a reference system within hemostasis hampers laboratories in establishing their laboratory performance over a prolonged period of time. Therefore, based on data from an external quality assessment program, we evaluated the between laboratory variation (CV BETWEEN ) and the long‐term within‐laboratory variation (LCV a ) for antithrombin, and proteins C and S. We evaluated the CV BETWEEN for the period 1996–2001, including the results of 64–240 laboratories from 23 different surveys (protein S activity 15 surveys). We observed a quite high CV BETWEEN and a broad range for each analyte. The CV BETWEEN was significantly higher for antithrombin and protein S for samples with low levels similar to heterozygous deficiencies. We also evaluated the LCV a , including the results of 136 laboratories. The lowest LCV a [median and 95% content interval (CI)] was observed for antithrombin (7.6%; 3.6–35.5%), intermediate values for protein C activity and antigen (8.6%; 3.5–25.3% and 10.8%; 4.8–33.1%, respectively) and highest values for the protein S variables (13.4%; 6.4–50.6% for total protein S antigen, 14.1%; 6.5–79.1% for free protein S antigen and 17.2%; 7.2–84.3% for protein S activity). We concluded that the main reason for the high CV BETWEEN is the long‐term within‐laboratory variability. Application of linear regression on data of an external quality assessment program is a useful model to demonstrate per analyte per laboratory the long‐term variability (LCV a ). It is concluded that improvement of the long‐term within‐laboratory test performance is the first priority in hemostasis to yield important improvements in the comparability and transferability of laboratory data.