Concerning the cut-off value of 3·3 μm for MPD, it had 66·9% (95% CI 58·1–74·9) specificity and 75·5% (95% CI 61·1–86·7) sensitivity in differentiating MYH9-RD and monoallelic or biallelic BSS from ITP. This evidence concerns the gene MYH9 and autoimmune thrombocytopenic purpura.