A coagulation sample drawn from a line shows a normal PT, prolonged aPTT, and prolonged thrombin time. What testing step is most appropriate first?

A coagulation sample drawn from a line shows a normal PT, prolonged aPTT, and prolonged thrombin time. What testing step is most appropriate first?

• A. Factor assays testing
• B. Mixing study
• C. Heparin neutralization
• D. Inhibitor assay

Answer: (C)

When a coagulation screen shows a normal PT with prolonged aPTT and prolonged thrombin time, the most likely culprit is heparin contamination in the sample. Thrombin time is very sensitive to even small amounts of heparin, so seeing TT prolonged alongside aPTT strongly points to the presence of heparin rather than a straightforward intrinsic-factor deficiency or inhibitor. The appropriate first step is to neutralize any heparin in the specimen and repeat the tests. If, after neutralization, the aPTT and TT normalize, you’ve confirmed that the prolongations were due to heparin contamination rather than an inherent clotting factor problem. If the prolongations persist despite neutralization, then proceed to other investigations to identify intrinsic pathway deficiencies or inhibitors, such as a mixing study to distinguish factor deficiency from inhibitors, followed by specific factor assays or inhibitor testing as indicated.

When a coagulation screen shows a normal PT with prolonged aPTT and prolonged thrombin time, the most likely culprit is heparin contamination in the sample. Thrombin time is very sensitive to even small amounts of heparin, so seeing TT prolonged alongside aPTT strongly points to the presence of heparin rather than a straightforward intrinsic-factor deficiency or inhibitor.

The appropriate first step is to neutralize any heparin in the specimen and repeat the tests. If, after neutralization, the aPTT and TT normalize, you’ve confirmed that the prolongations were due to heparin contamination rather than an inherent clotting factor problem. If the prolongations persist despite neutralization, then proceed to other investigations to identify intrinsic pathway deficiencies or inhibitors, such as a mixing study to distinguish factor deficiency from inhibitors, followed by specific factor assays or inhibitor testing as indicated.