Prothrombin time (PT) and/or activated partial Thromboplastin time (aPTT) are commonly performed in the cases of prolonged clotting time to evaluate further

Depending on the technology available , there are factor specific assays that use factor deficient plasma ( PT or APTT based ) , patient samples are compared to a calibration curve. Mixing tests with normal pool can assist in suggesting inhibitor vs deficiency.

Bleeding disorders are usually cost by

1) low platelet concentration

2) platelet integrity

3) factor deficiency

4) DIC

5) Accident etc

All these have the cause of such condition which I can't discuss here.

mixing studies are used to determine the specific clotting factor deficiency

Generally, Prothrombin Time (PT) and Partial Thromboplastin Time (PTT) can identify the clotting factors that belongs to each pathways. For PT, it can assess the Extrinsic and Common Pathway. On the other hand, PTT can assess Intrinsic and Common Pathway. In addition, specific mixing studies are used to determine the specific deficient clotting factor on each patient. For example, CFXIII is not assessed by PT and PTT. In order to assess CFXIII, CFXIII assay can be performed. Same goes with other clotting factors.

Clotting time (CT) is typically done to find bleeding disorder, most likely due to clotting factors deficiency. However, prolonged CT may also signify that there could be liver disorders, presence of circulating anticoagulants or lupus anticoagulants, tumors, or hypofibrinogenemia (< 100 mg/dL) present in the circulation. To further identify the cause of prolonged CT, specimen can be subjected to the following:

A. Tests to evaluate Intrinsic and Common Pathway

B. Tests to evaluate Extrinsic and Common Pathway

C. Tests for Fibrin Formation

D. Other Tests

E. Mixing Studies

F. Tests for Detection of Circulating and Lupus Anticoagulants

Since there are many factors that can affect these laboratory tests, a series of tests must be done to further identify the cause of these abnormal results. Correlating it with patient presentations can also help.

After a prolonged clotting time, multiple tests are needed to narrow down to a specific clotting factor or clotting factors a patient is deficient in. The secondary hemostasis involves a total of 15 clotting factors divided into 3 pathways- the intrinsic, extrinsic, and common. Although it may seem tedious to identify the problem in the secondary hemostasis, the tests commonly available in the laboratory are capable of isolating the specific deficiency without having to do unnecessary procedures.

Initially, physicians will request Activated Partial Thromboplastin Time (aPTT) and Prothrombin Time (PT) to isolate the pathway to which the deficient clotting factor belongs. A prolonged aPTT with normal PT is indicative of a deficiency in the intrinsic pathway; this involves clotting factors VIII, IX, XI, XII, Prekallikrein, and High Molecular Weight Kininogen. PT on the other hand tests only for one clotting factor, which is clotting factor VII of the extrinsic pathway. Hence, a prolonged PT and a normal aPTT immediately suggest a clotting factor VII deficiency. Lastly, a prolonged PT and aPTT is indicative of a deficiency in the common pathway; this involves clotting factors I, II, V, and X. After identifying the specific pathway the deficient clotting factor belongs to, a procedure known as mixing studies is performed. This procedure utilizes different preparation or mixture of plasma or serum to specifically identify the deficient clotting factor. Nevertheless, mixing studies is not the endpoint procedure and it may require further testing in some cases.

Identifying the specific clotting factor deficient in a patient is crucial in determining which treatment to give. Blood products such as cryoprecipitate or fresh frozen plasma (FFP) are some of the blood products processed and given in cases of clotting factor deficiency.

Good day, Lyka Janielle!

There are multiple tests that can be performed in order to identify deficient clotting factors. In addition, abnormal clotting time (CT) does not necessarily indicate deficiencies, it may also be caused by inhibitors.

Usually, initial tests performed are PT and PTT to identify which pathway the supposed deficient clotting factor belongs to. From there, mixing studies are performed to sift through the clotting factors.

You may read my reference to your question if you wish for a deeper understanding of coagulation tests:

Raber MN. Coagulation Tests. In: Walker HK, Hall WD, Hurst JW, editors. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition. Boston: Butterworths; 1990. Chapter 157. Available from: https://www.ncbi.nlm.nih.gov/books/NBK265/

After confirming that the PT or PTTK is prolong you go ahead and do a mixing studies, sometimes it could be an inbitor, but from the mixing studies you should be able to know the line of action.