FDP與D-Dimer報告不相符鑑別與解決之道

Discrepancy between FDP and D-Dimer Reports: Identification and Solutions

D-Dimer是排除栓塞性疾病的重要檢驗指標，但其結果有時會與臨床表現或FDP檢測不一致，導致判讀困難，因此釐清此類不一致結果之原因及其應對方式至關重要。本研究回顧2018至2020年間本院6064筆同時檢測FDP與D-Dimer（INNOVANCE D-Dimer kit，免疫比濁法）之數據，發現有35筆（0.577%）結果不一致。進一步於2022年8月至12月，針對27筆D-Dimer高於臨床閾值（>0.5 mg/L）但FDP正常(≦4.6μg/mL)的檢體，改用VIDAS D-Dimer Exclusion™II kit (酵素結合螢光分析法)複測，結果有8筆小於臨床決策閾值(<0.5 mg/L)，其中1筆經嗜異性抗體拮抗劑處理後，濃度下降達73.3%，顯示干擾可能源自非特異性抗體。研究指出，雖免疫比濁法檢測具便利性，仍可能受干擾產生偽陽性，如:虎克效應、嗜異性抗體及自體免疫抗體。建議當D-Dimer與臨床或FDP結果不一致時，可使用不同平台或拮抗劑進行確認，以提升檢驗準確性。

D-Dimer is an important diagnostic marker for excluding thromboembolic diseases. However, its results may sometimes be inconsistent with clinical presentations or FDP (fibrinogen degradation products) levels, leading to challenges in interpretation. Understanding the causes and management of these inconsistencies is therefore crucial. This study reviewed 6,064 cases from 2018 to 2020 in which both FDP and D-Dimer were tested simultaneously using the INNOVANCE D-Dimer kit (immunoturbidimetric assay) at our hospital, identifying 35 cases (0.577%) with discrepant results.
From August to December 2022, 27 samples with elevated D-Dimer levels (>0.5 mg/L) but normal FDP levels were reanalyzed using the VIDAS D-Dimer Exclusion™II kit (enzyme-linked fluorescent assay). Among them, 8 showed D-Dimer concentrations below the clinical threshold (<0.5 mg/L). One sample, after treatment with a heterophilic antibody blocking reagent, showed a 73.3% reduction in D-Dimer concentration, indicating interference likely due to non-specific antibodies.
The study highlights that while immunoturbidimetric assays offer convenience, they may yield false positives due to interferences such as the hook effect, heterophilic antibodies, or autoantibodies. When D-Dimer results are inconsistent with clinical findings or FDP levels, confirmation using alternative platforms or blocking reagents is recommended to ensure accuracy.