In this episode, I’ll discuss whether D-dimer results can be improved by adjusting cutoffs for renal dysfunction.
Patients with suspected thromboembolic disease who have a low or intermediate pretest probability often have a D-dimer level drawn as part of their workup before a decision to anticoagulate is made. The specificity of D-dimer is low, so when an elevated D-dimer is found this leads to further testing with ultrasound or IV contrast and CT scanning.
D-dimer levels are often elevated in patients with renal dysfunction due to decreased clearance, and this can lead to a false-positive result that would in turn lead to exposure of a patient with renal dysfunction to a CT scan with IV contrast. Acute renal failure is a possible consequence of such exposure.
Researchers in Switzerland conducted a retrospective study in over 15,000 patients using renal function adjusted cutoffs for D-dimer results. The usual positive D-dimer value cutoff of > 500 mcg/L was compared to > 333 mcg/L if GFR was above 60 mL/min, > 1306 mcg/L if GFR was 30-60, and > 1663 mcg/L if GFR was below 30.
When these adjusted cutoffs were applied, the number of false positives decreased by 49.9% in the GFR 30-60 group and by 55.8% in the GFR below 30 group.
Confirmation of these results in a prospective study could lead to reduced exposure to IV contrast media in patients who already have moderate or severe renal dysfunction.
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