The aPTT test evaluates how long it takes for blood to clot by measuring the functionality of certain coagulation factors such as Factors VIII, IX, XI, and XII. It is a crucial test used in conjunction with the prothrombin time (PT) to understand the complete coagulation profile of an individual. During the test, a blood sample is mixed with reagents, including a partial thromboplastin and calcium, and the time taken for the formation of a clot is recorded.
