The results showed that the sensitivity and specificity were 95.8 and 70%, respectively, when the plasma CNP level was >32.55 pg/mL (117); 76.9 and 91.7%, respectively, with a plasma norepinephrine level >3.59 pg/mL in upright position (38); and 90.5 and 78.6%, respectively, with a plasma copeptin level <10.2 pmol/L in predicting the efficacy of metoprolol in children with POTS (118). Here, CNP is linked to postural orthostatic tachycardia syndrome.