Clinical laboratory investigation of a patient with an extremely high D-dimer level: A case report.

Background: D-dimer, a soluble degradation product of cross-linked fibrin, is commonly used as an important marker for the diagnosis of disseminated intravascular coagulation and differential diagnosis of thrombosis. Herein, we present a geriatric case with an unusually elevated D-dimer level.

Case Summary: An 82-year-old woman, admitted to the ward with a diagnosis of chronic heart failure, was noted to have a remarkably elevated D-dimer level, beyond the qualified range (> 100 mg/L), utilizing the Innovating D-dimer for Sysmex CS-5100 System™. However, no evidence, including clinical symptoms, radiographic evidence of thromboembolic disease, and parallel fibrinogen degradation product values, suggested that this patient was at high risk of thrombopenia. To confirm the discrepancy, a series of approaches including sample dilution, re-analysis alternative methods, and sample treatment with blockage of specific heterophilic antibodies were performed. A remarkable disappearance of the elevated D-dimer values was observed in the samples after they were subjected to these approaches (4.49, 9.42, 9.06, and 12.58 mg/L, respectively). This confirmed the presence of heterophilic antibodies in this case. In addition, a reduction in cardiac output due to the presence of cardiac failure could also be responsible for the existence of a hypercoagulable state in this case.

Conclusion: In conclusion, the presence of heterophilic antibodies should be considered when an elevated D-dimer value is not in conformity with the clinical evidence, and a viral infection should be considered when interference by a heterophilic antibody exists.