Session: OR29-Adrenal Tumors & Pheochromocytoma
Room 134 (Moscone Center)
Design and Methods: P-NMN/MN/MTY were measured by liquid chromatography with tandem mass spectrometry in 765 patients at six centers, two of which complied with requirements for supine sampling after an overnight fast and four of which did not. Pheochromocytomas were found in 130 patients (67 non-compliant, 63 compliant) and not in 635 patients (195 non-compliant, 440 compliant).
Results: Sampling under non-compliant compared to compliant conditions resulted in 49%, 14% and 51% higher (P<0.001) median plasma concentrations of NMN (84.3 vs 56.5 pg/mL), MN (38.3 vs 33.5 pg/ml) and MTY (18.7 vs 12.4 pg/mL) in patients in whom pheochromocytomas were not found. Upper cutoffs were also higher under non-compliant compared to compliant conditions for NMN (237 vs 144 pg/mL), MN (95.7 vs 80.4 pg/ml) and MTY (70.7 vs 31.0 pg/mL). In contrast, plasma concentrations for NMN, MN and MTY were not higher when sampled under non-compliant versus compliant conditions in patients with pheochromocytoma. Use of upper-cut-offs calculated from data in patients without tumors sampled under non-compliant compared to compliant conditions resulted in substantially decreased diagnostic sensitivity (85.4% vs 97.7%). Use of upper-cut-offs calculated for compliant conditions was associated with a diagnostic specificity of only 71.3% for sampling under non-compliant conditions compared to 93.9% under compliant conditions.
Conclusions: High diagnostic sensitivity of P-NMN/MN/MTY for detection of PPGLs can only be guaranteed using upper-cut-offs of reference intervals appropriately calculated under supine fasting conditions. With appropriately estimated upper-cut-offs, sampling under seated non-fasting conditions can lead to a more than 4-fold increase in false-positive results necessitating repeat sampling under supine fasting conditions.
Nothing to Disclose: RD, MP, CP, KM, AP, MF, FB, AS, SRB, HPN, AJ, JWML, GE
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