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Presenting ADAMTS13 antibody and antigen levels predict prognosis in immune-mediated thrombotic thrombocytopenic purpura

Ferras Alwan, Chiara Vendramin, Karen Vanhoorelbeke, Katy Langley, Vickie McDonald, Steve Austin, Amanda Clark, William Lester, Richard Gooding, Tina Biss, Tina Dutt, Nichola Cooper, Oliver Chapman, Tanya Cranfield, Kenny Douglas, H. G. Watson, J. J. van Veen, Keith Sibson, William Thomas, Lynn Manson, Quentin A. Hill, Sylvia Benjamin, Debra Ellis, John-Paul Westwood, Mari Thomas and Marie Scully

Key points

  • High anti-ADAMTS13 antibody and low ADAMTS13 antigen levels adversely affect outcome in immune-mediated TTP with greater mortality seen.

  • A raised troponin at presentation confers a six-fold increase and reduced GCS a nine-fold increase in mortality in acute TTP.

Abstract

Immune-mediated Thrombotic Thrombocytopenic Purpura (TTP) is a life-threatening disorder caused by antibodies against ADAMTS13. From the United Kingdom TTP registry we undertook a prospective study investigating the impact of the presenting anti-ADAMTS13 IgG antibody and ADAMTS13 antigen on mortality. 312 episodes involving 292 patients over 87 months were included. 68% were female, median age 46 (range 11-88 years) and median presenting ADAMTS13 of <5% (range <5% – 18%). The mortality rate was 10.3% (n=32). 68% of patients had a raised troponin at presentation conferring a six-fold increase in mortality compared to those with normal troponin levels (12.1% vs. 2.0%, p=0.04). 24% had a reduced Glasgow Coma Score (GCS) at presentation with a nine-fold increase in mortality (20% vs. 2.2% for normal GCS at presentation, p<0.0001). Mortality increased with higher anti-ADAMTS13 antibody levels and lower ADAMTS13 antigen levels. Those with antibody levels in the upper quartile (antibody >77%) had a mortality of 16.9% compared to 5.0% for the lowest quartile (antibody <20%) (p=0.004). Those with an antigen level in the lowest quartile (antigen <1.5%) had a mortality of 18% compared to 3.8% for the highest quartile (antigen >11%) (p=0.005). The synergistic effect of anti ADAMTS13 IgG antibody in the upper quartile and ADAMTS13 antigen in the lowest quartile had the highest mortality of 27.3%. We conclude that both anti-ADAMTS13 IgG antibody and ADAMTS13 antigen levels correlate with outcome in TTP with increased cardiac and neurological involvement and increased mortality.

  • Submitted December 27, 2016.
  • Accepted May 2, 2017.