Incidence of thrombotic microangiopathies in Quebec: insight from a laboratory centralizing ADAMTS-13 testing

Abstract

Background: Thrombotic microangiopathies (TMA) are serious medical conditions requiring a prompt diagnosis to adapt treatment. The determination of ADAMTS-13 activity enables discriminating thrombotic thrombocytopenic purpura (TTP) from other forms of TMA. The purpose of this study was to provide an estimate of the incidence of TTP and TMA in the Canadian Quebec province using data collected from a laboratory centralizing ADAMTS-13 testing for the whole province.

Results: From 2012 to 2019, 846 patients were evaluated for plasma ADAMTS-13 activity due to a suspicion of TMA. TTP was identified in 147 patients. Of these, 118 patients with a median age of 51.5 years and a male-female ratio of 1:1.4 had their first episode of TTP during the study period. The number of ADAMTS-13 tests performed and the number of patients with suspected TMA increased annually by 19% and 21% respectively. While the incidence of non-TTP TMA increased annually, that for TTP remained unchanged. This averaged 10.2 (95% CI 5.9-14.4) per million persons per year for suspected non-TTP TMA and 1.8 (95% CI 1.3-2.4) for confirmed TTP. The incidence rate of TMA other than TTP was higher in the age group 70-79 years (21.8; 95% CI 5.4-38.1) for females and in the age group 80-89 years (24.4; 95% CI 7.2-41.7) for males compared to other age groups. The incidence rate of TTP was higher in the age group 40-49 years (4.0; 95% CI 2.0-5.9) for women and in the age group 60-69 years (3.4; 95% CI 1.1-5.6) for men compared to other age groups.

Conclusion: The analysis of centralized data measuring ADAMTS-13 activity allowed us to adequately establish the incidence rate and demographic characteristics of TMA, particularly TTP, in Quebec. TTP incidence remained stable while suspected non-TTP TMA steadily increased from 2012 to 2019.

Keywords: ADAMTS-13; Epidemiology; Incidence; Prevalence; Thrombotic microangiopathies; Thrombotic thrombocytopenic purpura.

Fig. 1

Flow chart of the study and patient categorization. ADAMTS-13 a disintegrin and metalloprotease with thrombospondin type 1 repeats, member 13, TMA thrombotic microangiopathy, TTP thrombotic thrombocytopenic purpura

Fig. 2

Trends in ADAMTS-13 testing and number of patients with clinically suspected thrombotic microangiopathy according to year. a Number of ADAMTS13 activity requests by year. b Number of patients with thrombotic microangiopathy other than TTP (non-TTP TMA) suspicion (white) and with TTP (grey) by year

Fig. 3

Age distribution of patients tested for ADAMTS-13 activity from 2012 to 2019 according to gender. a Patients with thrombotic microangiopathy other than TTP (non-TTP TMA). b Patients with TTP

Fig. 4

Mean annual incidence rate by age group and gender. a Clinically suspected thrombotic microangiopathy other than TTP (non-TTP TMA) (n = 666). b Confirmed TTP (n = 118). The incidence rate has been extrapolated for year 2012