Given the laboratory results of a patient admitted after an accident, which factor deficiency is most likely indicated by the tests results: Platelet count 200,000/mm³, PT 19.2 sec (control 14.8 sec), PTT 28.4 sec (control 27.6 sec)?

The laboratory results indicate a prolonged prothrombin time (PT) while the activated partial thromboplastin time (PTT) remains within normal limits. PT is primarily affected by the extrinsic pathway of coagulation, which involves factors such as Factor VII. Since the PT is significantly longer than the control value, this suggests a deficiency or dysfunction in one of the factors involved in the extrinsic pathway, and Factor VII is the key factor responsible for the PT.

While factors V, X, and XIII may influence coagulation, they do not primarily affect PT to this degree. Factor V and Factor X are involved in the common pathway, which would typically prolong both PT and PTT if deficient. Factor XIII is essential for crosslinking fibrin but does not have a direct effect on PT or PTT measurement, hence it would not be responsible for the isolated PT prolongation observed in this scenario.

Thus, the test results strongly indicate a deficiency in Factor VII, aligning with the prolonged PT while the PTT remains relatively normal. This is characteristic of issues in the extrinsic pathway and underscores why Factor VII deficiency is the most likely conclusion based on the provided data.