Background
Low ADAMTS-13 levels have been repeatedly associated with an increased risk of ischemic stroke, but results concerning the risk of myocardial infarction are inconclusive.

Objectives
To perform an individual patient data meta-analysis from observational studies investigating the association between ADAMTS-13 levels and myocardial infarction.

Methods
A one-step meta-analytic approach with random treatment effects was used to estimate pooled odds ratios (ORs) and corresponding 95% confidence intervals (CIs) adjusted for confounding. Analyses were based on dichotomous exposures, with the 5th and 1st percentiles of ADAMTS-13 antigen levels as cut-off values. Quartile analyses, with the highest quartile as a reference category, were used to assess a graded association between levels and risk (‘dose’ relationship). Additionally, we assessed the risk of the combined presence of low ADAMTS-13 and high von Willebrand factor (VWF) levels.

Results
Five studies were included, yielding individual data on 1501 cases and 2258 controls (mean age of 49 years). Low ADAMTS-13 levels were associated with myocardial infarction risk, with an OR of 1.89 (95% CI 1.15–3.12) for values below the 5th percentile versus above, and an OR of 4.21 (95% CI 1.73–10.21) for values below the 1st percentile versus above. Risk appeared to be restricted to these extreme levels, as there was no graded association between ADAMTS-13 levels and myocardial infarction risk over quartiles. Finally, there was only a minor synergistic effect for the combination of low ADAMTS-13 and high VWF levels.

Conclusions
Low ADAMTS-13 levels are associated with an increased risk of myocardial infarction.