A Case of False Decrease of Plasma D-Dimer

Background: D-dimer, a specific product of cross-linked fibrin degradation, is of great clinical value in the early diagnosis of thrombotic diseases and in monitoring the efficacy of thrombolysis; therefore, the accuracy of D-dimer test results is crucial. Methods: This article reports a case of a patient with disseminated intravascular coagulation (DIC) who experienced a false decrease in D-dimer due to the hook effect. Results: The three D-dimer test results for DIC patients were 1.09 mg/L, 0.93 mg/L, and 1.43 mg/L. After sample dilution, the results were: first time (1:128) 842.24 mg/L, second time (1:128) 1,505.28 mg/L, third time (1:32) 415.68 mg/L. There was a significant difference in the three test results before and after dilution, because the D-dimer concentration was too high, exceeding the detection range and causing the hook effect, which falsely lowered the D-dimer value. Conclusions: When the D-dimer value of DIC patients does not match the clinical situation, the possibility of the hook effect should be considered, and the false decrease can be ruled out by the sample dilution method. In this way, accurate clinical results can be obtained to avoid delaying the diagnosis and treatment of DIC patients. (Clin. Lab. 2024;70:1412-1415. DOI: 10.7754/Clin.Lab.2024.240223)