2022 Volume 71 Issue 2 Pages 330-334
The activated partial thromboplastin time (APTT) test is one of the laboratory tests for screening for coagulation disorders, and it is known that coagulation tests including the APTT test are affected by blood collection and centrifugation conditions. Therefore, it is recommended that clotting time assays be performed in accordance with the “Consensus on standardization of sample preparation for clotting time assays” proposed by the Japanese Society of Laboratory Hematology-organized Working Group for Standardization of Sample Preparation for clotting time assays. In our case, the prolongation of APTT was frequently observed, and most patients did not have anticoagulant therapy or a condition that could cause the prolongation of APTT. Since there was no abnormality in the reagents or equipment, and the sample preparation was in accordance with the consensus, the possibility of a defective blood collection tube was considered, and APTT prolongation was not observed when a different lot of blood collection tubes was used. We inquired from the manufacturer and they replied that the citric acid concentration was more than twice the normal level due to human error during the manufacturing process. In conclusion, it is necessary to consider not only abnormalities in reagents and equipment but also unexpected tube failure when APTT prolongation is frequently observed. Furthermore, thorough adherence to the consensus on the standardization of sample preparation for clotting time assays will lead to early resolution when an unexplained abnormal clotting time is encountered.
