A patient admitted to the hospital with thrombosis is given the standard heparin dosage. Twenty-four hours after the heparin is started, the PTT is 38 seconds (reference range, 25 to 37 seconds). Both normal and abnormal controls are within their limits. Which of the following is most likely?

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Quizplus · Accepted Answer

A prolonged PTT can be a sign of inadequate anticoagulation therapy. If both normal and abnormal controls are within their limits, a laboratory error is unlikely. Heparin-induced thrombocytopenia is associated with a decrease in platelet count, but this information is not provided in the question stem. Switching to LMWH may be considered, but the question stem does not provide enough information to make this determination. Low antithrombin levels can lead to a higher heparin requirement, resulting in a longer PTT despite standard dosing.

A Patient Admitted to the Hospital with Thrombosis Is Given