Abstract
IntroductionThe diagnosis of thrombotic microangiopathy (TMA) relies on common biological parameters which diagnostic value is unknown.MethodsThe presence of common biological parameters was assessed in 967 patients with TMA during the 2009-2023 period (ClinicalTrials.gov: NCT05991245).ResultsMedian age was 49 [36-64] and 53.2% were male. All TMA causes were represented (atypical hemolytic uremic syndrome (HUS): 41.6%; drugs: 24.9%; malignancy: 21.4%; auto-immune: 18.8%; infection: 7.6%, complement-mediated HUS (C-HUS): 6.8%, organ transplantation: 5.8%, pregnancy: 3.8%, bone marrow transplantation (BMT): 2.9%, shigatoxin (STEC-HUS): 0.6%, thrombotic thrombocytopenic purpura (TTP) (0.6%).The presence of TMA-related parameters concerned virtually all patients with TTP but varied widely for the other patients: anemia 81.7% (anemia (81.7%), high lactate deshydrogenase (LDH) (75.4%), low haptoglobin (53.7%), thrombocytopenia (40.3%). Their diagnostic performance was accurate only for TTP. Eleven distinct ways were used for schistocyte metrics and reporting. Relying on schistocytes presence as the single diagnostic criterion would lead to missed diagnosis in 23.8% (shigatoxin HUS) to 86.4% (bone marrow transplantation) of patients (for anemia: 8.2% to 22.3%; thrombocytopenia: 31.8% to 67.9%; high LDH: 10.0% to 40.7%, low haptoglobin: 0% to 70.4%, according to the causes of TMA). The overall risk of missed diagnosis using these parameters was ≥ 50% in all TMA, except in TTP.The best diagnostic performances were obtained when fibrinogen levels were <5 g/L, creatinine ≥300 μmol/L, prothrombin time (PT) <90% and when TMA causes were TTP, STEC-HUS, infection or complement-mediated HUS.ConclusionsCommon biological parameters miss the diagnosis in more than 50% of TMA except when fibrinogen is <5 g/L, creatinine ≥300 μmol/L and prothrombin time (PT) <90%. Schistocyte reporting is heterogenous, and its results are usually deceptive in TMA.