Screening Tests: Summary
Summary
The following table provides a summary of the results obtained using the PT, APTT, Fibrinogen and Thrombin Time in various disorders.
| Platelet Count | PT | APTT | TT | Fibrinogen | Interpretation |
|---|---|---|---|---|---|
| Normal | Normal | Normal | Normal | Normal | Normal profile Factor XIII deficiency Mild VWD Qualitative platelet disorder Connective tissue problem e.g. Ehlers Danlos Mild coagulation factor deficiency |
| Normal | ↑ | Normal | Normal | Normal | FVII deficiency |
| Normal | Normal | ↑ | Normal | Normal | FVIII, FIX, FXI or FXII deficiency VWD - if the FVIII level is reduced Lupus anticoagulant [Occasionally a very strong lupus anticoagulant or a lupus anticoagulant that has anti-prothrombin activity can result in a prolonged PT. Similarly a lupus anticoagulant can also be associated with thrombocytopaenia.] Other contact factor deficiency |
| Normal | ↑ | ↑ | Normal | Normal | 'Common pathway' deficiency i.e. FII, FV or FX deficiency Multiple clotting factor deficiencies e.g. combined FV and FVIII deficiency Warfarin or vitamin K antagonist Vitamin K deficiency or a mutation within one of the genes encoding key enzymes involved in VK metabolism. Occasionally a very strong Lupus anticoagulant can cause these findings but it is unusual to see a prolongation of the PT with a LA due to the high concentration of PL used in the PT test. |
| ↓ | ↑ | ↑ | ↑ | ↓ | DIC Massive transfusion Liver disease |
| ↓ | Normal | Normal | Normal | Normal | Primary platelet problem e.g. ITP. The Mean Platelet Volume [MPV] can be helpful in establishing the causes of thrombocytopaenia. A raised MPV is often associated with increased peripheral destruction e.g. ITP - whereas a reduced MPV is often seen in association with bone marrow failure. Changes in the MPV are also seen in patients with various inherited platelet disorders e.g. Wiskott Aldrich syndrome |
Data Interpretation
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