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

Am J Hematol. 2017 Apr;92(4):381-387. doi: 10.1002/ajh.24665. Epub 2017 Feb 21.


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 < .001) were retained as risk factors of misdiagnosis. Platelet count recovery was significantly longer in the misdiagnosed group (P = .041) without consequence on mortality, exacerbation and relapse. However, patients in the misdiagnosed group had a less severe disease than those in the accurately diagnosed group, as evidenced by less organ involvement at TTP diagnosis (P = .006). TTP is frequently misdiagnosed with autoimmune cytopenias. A low schistocyte count and a positive DAT should not systematically rule out TTP, especially when associated with organ failure.

MeSH terms

  • ADAMTS13 Protein / deficiency
  • Adult
  • Anemia, Hemolytic, Autoimmune / diagnosis
  • Antibodies, Antinuclear / analysis
  • Coombs Test
  • Diagnosis, Differential
  • Diagnostic Errors*
  • Female
  • Hemoglobins / analysis
  • Humans
  • Male
  • Middle Aged
  • Prognosis
  • Purpura, Thrombocytopenic, Idiopathic / diagnosis*
  • Purpura, Thrombotic Thrombocytopenic / diagnosis*
  • Risk Factors
  • Sex Factors


  • Antibodies, Antinuclear
  • Hemoglobins
  • ADAMTS13 Protein

Supplementary concepts

  • Thrombotic thrombocytopenic purpura, acquired