A patient's aPTT is prolonged. On 1:1 mixing with pooled normal plasma, the aPTT corrects immediately. After incubating the mixture at 37 degrees Celsius for 60 minutes, the aPTT prolongs again. This pattern indicates:
- A A time-dependent factor VIII inhibitor ✓
- B A specific factor inhibitor such as factor VIII antibody
- C Simple factor VIII deficiency
- D Heparin contamination of the sample
Correct answer: A. A time-dependent factor VIII inhibitor
Explanation
Immediate correction on mixing indicates absence of an immediate-acting inhibitor, while reappearance of prolongation after incubation is characteristic of a time-dependent inhibitor, classically a factor VIII antibody seen in acquired hemophilia. Simple factor deficiency corrects fully and stays corrected. Heparin contamination would not show this time-dependent pattern and is excluded by a thrombin time test.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.