Biochemical diagnosis strategy in pheochromocytoma
Ana-Maria Stefanescu1, Sorina Schipor1, Diana-Loreta Paun1, Constantin Dumitrache2 & Corin-Virgil Badiu2
Objective: The best biochemical strategy to follow in pheochromocytoma clinical diagnosis.
Patients and methods: We selected two groups of patients: 24 pheochromocytomas (further diagnosed by CT): 20 women and 4 men aged 2068 years and a normotensive group: 100 subjects without endocrine disfunction: 83 women and 17 men aged 1970 years. In both groups we tested five parameters: plasma normetanephrines/metanephrines (NMNp/MNp); urine normetanephrines/metanephrines (NMNu/MNu) and chromogranin A (CgA) by Elisa and established median values as it follows: NMNp: 688 vs 31.5 pg/ml; MNp: 224.5 vs 15 pg/ml; NMNu: 1526 vs 311 μg/24 h; MNu: 307 vs 88 μg/24 h; CgA: 269.5 vs 74.5 ng/ml. Then we applied the analysis of receiver operating characteristic curves (ROC) with a statistical comparison between ROC curves. The software relies on a non-parametric test for the difference of the area under the ROC curve (AUC). For each parameter assayed we calculated optimal threshold values corresponding to the maximal accuracy: NMNp: 100 pg/ml; MNp: 89 pg/ml; NMNu: 741 μg/ml; MNu: 486 μg/ml; CgA: 117 ng/ml. AUC values were established for each parameter in decreased order: NMNp: 0.9783; NMNu: 0.9521; MNp: 0.9285;CgA: 0.8733; MNu: 0.8490. AUC differences between different parameters and the confidence intervals (95% CI) were also calculated: NMNp/MNp: 0.0498 (−0.03404, 0.13363); NMNp/NMNu: 0.0263 (−0.03404, 0.13363); NMNp/MNu: 0.1294 (0.02400, 0.23475), NMNp/CgA: 0.1050 (0.01374, 0.19626), MNp/NMNu: −0.0235 (−0.11494, 0.06785); MNp/MNu: 0.0796 (−0.03630, 0.19547), MNp/CgA: 0.0552 (−0.06270, 0.17312); NMNu/MNu: 0.1031 (−0.00818, 0.21444); NMNu/CgA: 0.0788 (−0.01197, 0.16947); MNu/CgA: −0.0244(−0.16229, 0.11354). Significant AUC differences were established between NMNp/CgA: P=0.0241 and between NMNp/MNu: P=0.0161.Our statistics revealed NMNp as the best diagnosis marker for pheochromocytoma, followed in decreased order by NMNu, CgA, MNp, MNu.
Conclusions: Plasma NMNp proved to be the best biochemical test for clinical diagnosis of pheochromocytoma.