Progressive Care Nursing Certification (PCCN) Practice Exam

What abnormal lab result is indicative of heparin-induced thrombocytopenia (HIT)?

1. A marked increase in creatinine

2. A decrease in platelet count by 50% of baseline

3. An increase in blood urea nitrogen (BUN)

4. An elevated international normalization ratio (INR)

The correct answer is: A decrease in platelet count by 50% of baseline

The correct answer reflects a key indicator of heparin-induced thrombocytopenia (HIT), where a decrease in platelet count by 50% of baseline is specifically associated with this condition. HIT is an immune-mediated reaction to heparin that leads to thrombocytopenia (a low platelet count) due to the formation of antibodies against the heparin-platelet factor 4 complex. This drop in platelet count is a critical diagnostic criterion for HIT and typically occurs 5-14 days after the start of heparin therapy, or sooner in patients who have been previously exposed to heparin. In the context of the other options, a marked increase in creatinine, an increase in blood urea nitrogen (BUN), and an elevated international normalization ratio (INR) do not specifically relate to HIT. While renal impairment (indicated by changes in creatinine and BUN) and coagulation status (as indicated by INR) are significant considerations in the management of patients on anticoagulation therapy, they are not direct diagnostic markers for HIT. Therefore, a significant reduction in platelet count is the distinct observation that points towards this complication, thus making it the correct and relevant choice.