CLSI H47
One-Stage Prothrombin Time (PT) Test and Activated Partial Thromboplastin Time (APTT) Test
This guideline outlines standardized procedures for performing and interpreting PT (Prothrombin Time) and APTT (Activated Partial Thromboplastin Time) tests using citrated plasma. It ensures accuracy in coagulation testing by addressing preanalytical and analytical variables, method standardization, and clinical relevance, including international PT normalization.
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{{FormatPrice(nonMemberPrice)}} List PriceClinical and Laboratory Standards Institute document H47—One-Stage Prothrombin Time (PT) Test and Activated Partial Thromboplastin Time (APTT) Test describes the principles and procedures necessary for the routine performance of the PT and APTT by conventional techniques using citrated plasma. Each of the two tests measures the time for a fibrin clot to develop in test plasma after activation. The chemical reactions are complex and, characteristically, results are affected by preexamination (preanalytical) and examination (analytical) variables. The PT and APTT are important screening tests used in laboratory evaluation of patients suspected to have disorders of blood coagulation, including the presence of circulating coagulation inhibitors. The PT measures the extrinsic or tissue factor pathway of the coagulation system and is used to monitor vitamin K antagonist therapy. The APTT measures the intrinsic coagulation pathway and is used in monitoring heparin therapy, as well as parenteral direct thrombin inhibitor anticoagulant therapy such as argatroban and lepirudin. The objective of this guideline is to improve test reproducibility through standardization of technique and ensure clinical relevance by setting test performance goals. The document also highlights the international effort for standardization of the PT through the use of the international normalized ratio.
This guideline was revised in 2023 under the Limited Revision Process and replaces the second edition of the guideline, which was published in 2008.
Several changes were made in this edition, including:
• Adding new anticoagulants
• Adding effect of hemophilia therapies on APTT
• Adding new references
H47 provides general guidelines for performing PT and APTT tests with the conventional method of using citrated, platelet-poor plasma. It does not cover alternative methods of using citrated whole blood or capillary blood obtained by the fingerstick method. Nonclotting-based, end-point–detection tests, such as chromogenic substrate assays, are also not discussed.
This document is available in electronic format only.
Clinical and Laboratory Standards Institute document H47—One-Stage Prothrombin Time (PT) Test and Activated Partial Thromboplastin Time (APTT) Test describes the principles and procedures necessary for the routine performance of the PT and APTT by conventional techniques using citrated plasma. Each of the two tests measures the time for a fibrin clot to develop in test plasma after activation. The chemical reactions are complex and, characteristically, results are affected by preexamination (preanalytical) and examination (analytical) variables. The PT and APTT are important screening tests used in laboratory evaluation of patients suspected to have disorders of blood coagulation, including the presence of circulating coagulation inhibitors. The PT measures the extrinsic or tissue factor pathway of the coagulation system and is used to monitor vitamin K antagonist therapy. The APTT measures the intrinsic coagulation pathway and is used in monitoring heparin therapy, as well as parenteral direct thrombin inhibitor anticoagulant therapy such as argatroban and lepirudin. The objective of this guideline is to improve test reproducibility through standardization of technique and ensure clinical relevance by setting test performance goals. The document also highlights the international effort for standardization of the PT through the use of the international normalized ratio.
This guideline was revised in 2023 under the Limited Revision Process and replaces the second edition of the guideline, which was published in 2008.
Several changes were made in this edition, including:
• Adding new anticoagulants
• Adding effect of hemophilia therapies on APTT
• Adding new references
H47 provides general guidelines for performing PT and APTT tests with the conventional method of using citrated, platelet-poor plasma. It does not cover alternative methods of using citrated whole blood or capillary blood obtained by the fingerstick method. Nonclotting-based, end-point–detection tests, such as chromogenic substrate assays, are also not discussed.
This document is available in electronic format only.