Plasma free metanephrine and normetanephrine levels are increased in patients with chronic kidney disease.

OBJECTIVE

Patients with impaired renal function, particularly those on dialysis, frequently exhibit high blood pressure and hemodynamic instability, which often lead to pheochromocytoma assessment. Our objective was to assess plasma free metanephrine (MN) and normetanephrine (NMN) in chronic kidney disease patients (CKD) with or without dialysis.

METHODS

In this prospective observational study we performed enzyme-linked immunosorbent assays (ELISAs) to evaluate plasma free MN and NMN in 48 CKD patients (15 with stage 3-5 CKD without dialysis, 26 on hemodialysis [HD], and 7 continuous ambulatory peritoneal dialysis [CAPD]), 30 patients with histologically proven pheochromocytoma, and 43 hypertensive patients. Adrenal masses were ruled out by abdominal computed tomography (CT) scans in all CKD and control hypertensive patients.

RESULTS

All 3 CKD groups (HD, CAPD, and CKD without dialysis) had significantly higher plasma free MN and NMN levels than the control hypertensive group (P<.0055). HD and CAPD patients had significantly lower plasma free NMN (P<.0055), but free MN levels were not significantly different than those observed in pheochromocytoma patients. In patients with HD, CAPD, and CKD without dialysis, plasma free MN and NMN were higher than manufacturer's upper limits of normal in 57.7% and 28.5%, 13.3% and 61.5%, and 85.7% and 26.6%, respectively. Regression models showed that the number of dialysis years was significantly correlated with plasma free MN (r = 0.615, P<.001) but not free NMN.

CONCLUSION

Plasma free MN and NMN levels are frequently elevated in CKD patients, particularly in those on dialysis. Plasma free MN levels significantly overlap with the range in pheochromocytoma patients and correlate with the number of years on dialysis.