Falsely elevated D-dimer partially caused by heterophilic antibodies: A case report.

Plasma D-dimer is a screening marker for thrombosis and hemostasis disorders. Falsely elevated D-dimer may result in misdiagnosis and potentially invasive investigations. Therefore, identifying falsely elevated D-dimer is of great value in laboratory practice. D-dimer is determined by immunoassay and vulnerable to heterophilic antibody interference. Here, we reported a case of falsely elevated D-dimer partially caused by heterophilic antibodies. Dilution test, polyethylene glycol precipitation, heterophilic blocking reagent and method comparison were used to identify the heterophilic antibody interference. All these methods, except for the heterophilic blocking reagent, revealed the existence of heterophilic antibody interference. Polyethylene glycol precipitation failed to reduce the D-dimer to its reference interval. Therefore, we conclude that the falsely elevated D-dimer is partially caused by heterophilic antibody interference.