Thrombotic thrombocytopenic purpura misdiagnosed as autoimmune cytopenia: Causes of diagnostic errors and consequence on outcome. Experience of the French thrombotic microangiopathies reference centre

Abstract

Thrombotic thrombocytopenic purpura (TTP) has a devastating prognosis without adapted management. Sources of misdiagnosis need to be identified to avoid delayed treatment. We studied 84 patients with a final diagnosis of severe (<10%) acquired ADAMTS13 deficiency-associated TTP from our National database that included 423 patients, who had an initial misdiagnosis (20% of all TTP). Main diagnostic errors were attributed to autoimmune thrombocytopenia, associated (51%) or not (37%) with autoimmune hemolytic anemia. At admission, misdiagnosed patients were more frequently females (P =.034) with a history of autoimmune disorder (P =.017) and had organ involvement in 67% of cases; they had more frequently antinuclear antibodies (P =.035), a low/undetectable schistocyte count (P =.001), a less profound anemia (P =.008), and a positive direct antiglobulin test (DAT) (P =.008). In multivariate analysis, female gender (P =.022), hemoglobin level (P =.028), a positive DAT (P =.004), and a low schistocytes count on diagnosis (P