In the individual San Diego, Phoenix and Boston cohorts (Table 1), the mean serum NOTCH3-ECD levels were similar between individuals with IPAH (mean ± s.d., 19.2 ± 5.0 ng ml−1, 20.3 ± 5.9 ng ml−1 and 20.2 ± 7.0 ng ml−1, respectively; P = 0.33) (Fig. 1b). Here, NOTCH3 is linked to idiopathic pulmonary arterial hypertension.