D‐dimer level > 4000 mcg/L FEU but one other criterion not met (i.e. either timing, thrombosis, thrombocytopenia, anti‐PF4 antibodies) or D‐dimer level 2000–4000 mcg/L FEU/unknown with all other criteria present. The gene discussed is PF4; the disease is Thrombocytopenia.