Which factor deficiency correlates with a PT of 22 seconds, aPTT of 79 seconds, and a fibrinogen level of 0.5 g/L?

The scenario presented indicates a prolonged prothrombin time (PT) of 22 seconds, an activated partial thromboplastin time (aPTT) of 79 seconds, and a significantly low fibrinogen level of 0.5 g/L. In this context, the most relevant factor deficiency is related to fibrinogen, which is also known as Factor I.

Fibrinogen plays a crucial role in the coagulation cascade, as it is the soluble precursor to fibrin, which is essential for clot formation. A low fibrinogen level can lead to impaired coagulation, resulting in prolonged PT and aPTT. The PT measures the extrinsic and common pathways of coagulation involving factors like I, II, V, VII, and X, while the aPTT assesses the intrinsic and common pathways, involving factors I, II, V, VIII, IX, X, XI, and XII.

In the case of a severe fibrinogen deficiency, both PT and aPTT can be prolonged due to the direct impact on the formation of a stable fibrin clot. The extreme reduction in fibrinogen level (0.5 g/L) suggests a significant deficiency, consistent with the laboratory findings.

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