Blood clotting tests (aka coagulation tests, coagulation screen, coags) are lab tests used to Dx hemostasis. A coagulometer makes analytics based on diffrent methods of activation and observation of development of blood clots in blood [or its plasma].

• The coagulation cascade results from injury to a blood vessel's endothelial lining, causing activation, adhesion, and aggregation of platelets, resulting ultimately to deposition and maturation of fibrin
• Although in the lab, the pathway can begin either with the intrinsic or extrinsic pathways, in real life, it can only do so from the extrinsic arm. During the cascade, the extrinsic arm is turned off, as there is sufficient thrombin to continue propagating the intrinsic arm

• Platelet count
• Bleeding time for platelet function
• PR (prothrombin ratio) for the tissue factor pathway (extrinsic pathway). PTT (prothrombin time test, aka internationalized normalized ratio, INR) is a ratio of a Pt's PT (prothrombin time) to the PT of a normal sample of blood. Thus, a result of 1-1.5 is considered normal. A result <1 means blood is too thick (clots too easily), or if >1 means blood is too thin (doesn't clot enough). It is primarily used to monitor warfarin therapy, where the aim is to maintain an elevated INR within a certain range, e.g. 2-3. The TG's (publishd Dec 2019), INR indicates the extent of anticoagulation for Pt's taking warfarin, and depends on indication for threapy; it shouldn't be sloely used to determine bleeding risk
• aPTT (activated partial thromboplastin time), which tests the contact activation pathway (intrinsic pathway)
• TCT or fibrinogen assay for the final common pathway (thrombin time)

More detailed and specific coagulation tests, include:

• Specific factor assays, including:
  • Fibrin degradation products
  • D-dimer, indicating possibility of completed thrombosis
  • Thrombin time
  • Platelet aggregation
• Specific factor inhibitor assays, including:
  • Protein C
  • TFPI
  • Antithrombin

• Blood count (often performed together, to detect other hematological abnormalities)
• LFT's (to exclude liver disease, as a cause of coagulation factor deficiency)