Furthermore, transplant-free survival estimation was performed based on the cutoff values introduced by ROC analysis of single proteins and for all the possible combinations (Methods and Extended Data Fig. 9), in which we confirmed NID1 and SPARCL1 can discriminate PAH participants with poorer transplant-free survival (log-rank P value = 0.007 and 0.002, respectively), while NID1 in combination with each of the other proteins (SPARCL1, C1QTNF1 or MEGF9) remained significantly predictive. This evidence concerns the gene SPARCL1 and pulmonary arterial hypertension.