Preanalytical Variables in Coagulation Testing: Setting the Stage for Accurate Results

Abstract

Many preanalytical variables may affect the results of routine coagulation assays. While advances in laboratory instrumentation have partially addressed the laboratory's ability to recognize some of these variables, there remains an increased reliance on laboratory personnel to recognize the three potential areas where coagulation testing preanalytical issues may arise: (1) specimen collection (including patient selection), (2) specimen transportation and stability, and (3) specimen processing and storage. The purpose of this article is to identify the preanalytical variables associated with coagulation-related testing and provide laboratory practice recommendations in an effort to improve the quality of coagulation testing and accuracy of result reporting.

Recommendations for clinical laboratory testing for protein C deficiency, for the subcommittee on plasma coagulation inhibitors of the ISTH

“…Blood for PC assays should be taken into standard coagulation blood draw tubes and maintained at room temperature, and plasma prepared using good laboratory practice . Plasma can be tested fresh, within 4 hours of venipuncture, or must be frozen within the 4‐hour window if testing is to be postponed.…”

“…Plasma can be tested fresh, within 4 hours of venipuncture, or must be frozen within the 4‐hour window if testing is to be postponed. The 4‐hour window can be extended for a particular assay if there is in‐house validation . Samples can be frozen below −20°C for up to 2 weeks (not in a self‐defrosting freezer) or up to 18 months below −70°C.…”

Editorial Compilation VIII

“…Thus, this report should be of interest to laboratory personnel who otherwise may struggle on the number of "acceptable" freeze-thaw cycles for hemostasis testing, and this report provides specific insight into other preanalytical variables in coagulation testing. 29 We again thank all the authors of this latest issue of "Editorial Compilations" for their original and comprehensive contributions, and we hope our readership enjoys this new installment in this series.…”

Effect of Multiple Freeze–Thaw Cycles on Coagulation Testing

“…A recent publication in this journal identified numerous potential sources of variables that may alter the results of coagulation testing. 1 Storage of blood samples is one identified area where potential sources of test bias may occur, especially when storage is compromised or not optimal. For freshly collected samples that cannot be tested within the recommended time frame for measurand stability, plasma is separated by centrifugation (ideally with double centrifugation to ensure depletion of platelets 2 ), stored in capped polypropylene storage vials, and maintained frozen, preferably at À70°C or colder.…”