Clinical and Laboratory Standards Institute H21—Collection, Transport, and Processing of Blood Specimens for Testing Plasma-Based Coagulation Assays provides procedures for the collection, transport, and processing of blood specimens for plasma-based coagulation testing. Samples referred for coagulation testing are susceptible to preexamination errors, including those resulting from specimen collection and mixing, storage and transportation, various patient factors, and exogenous interferences. Thus, attention to these errors is important. CLSI H21 is primarily for laboratory and/or clinical personnel responsible for performing and interpreting plasma-based coagulation assays.

This guideline replaces CLSI H21-A5, published in 2008. Several changes were made to this edition. One of the most prominent changes involved reorganizing the content into a process with multiple procedures, which is consistent with CLSI instilling QMS principles into its documents. CLSI H21 articulates a sequence of chronological procedures that comprise the process of successful collection, transport, and processing of human specimens for plasma-based coagulation testing. The quality system essentials (QSEs) are foundational building blocks that function effectively to support the laboratory’s path of workflow. Although not all aspects of the QSEs may be mandatory, adherence to the QSEs ensures that the specimen collection, transport, and processing for plasma-based coagulation testing is performed at a higher level of overall quality. Other changes include: • Removing guidelines for molecular hemostasis assays • Adding a discussion of preexamination patient factors that may affect coagulation tests (Subchapter 2.3) • Adding a list of specimen collection issues of particular relevance to plasma-based coagulation testing (Subchapter 3.2) • Adding a discussion of unconventional samples sent for coagulation testing (Subchapter 3.2.2) • Removing the recommendation for 129 mmol/L, 3.8% dehydrate form of trisodium citrate • Adding recommendations for the stability of whole blood samples when stored at room temperature (Chapter 4) • Adding a discussion of sample preexamination issues (eg, hemolysis, icterus, lipemia) and interferences (eg, anticoagulants, coagulation factor concentrates) (Subchapter 5.4) • Updating the recommendation for the stability of fresh and frozen plasma samples (Chapters 6 and 7) • Updating the list of specimen rejection criteria (Chapter 8) • Adding a discussion on troubleshooting preexamination issues (Subchapter 8.2) • Updating references • Adding Appendix A for commonly misordered coagulation tests

CLSI H21 discusses procedures for the collection, transport, and processing of human specimens for plasma-based coagulation testing. The intended audience includes laboratory and clinical personnel responsible for performing and interpreting plasma-based coagulation testing and manufacturers of products involved in specimen collection, storage, and preparation, as well as testing of plasma-based coagulation assays. CLSI H21 does not cover whole blood coagulation assays, platelet function tests, thrombin generation assays, point-of-care coagulation testing, or molecular coagulation assays. CLSI H21 also does not provide general guidelines for performing coagulation testing. Guidelines for performing specific coagulation assays are provided in other CLSI documents that cover prothrombin time (PT) and activated partial thromboplastin time (APTT) assays (CLSI H47, CLSI H54), factor activity assays (CLSI H48), fibrinogen assays (CLSI H30), D-dimer assays (CLSI H59), lupus anticoagulant (LA) assays (CLSI H60), and point-of-care coagulation testing (CLSI POCT14).