Measurements of plasma metanephrines by immunoassay vs liquid chromatography with tandem mass spectrometry for diagnosis of pheochromocytoma

Abstract

Background: Reports conflict concerning measurements of plasma metanephrines (MNs) for diagnosis of pheochromocytomas/paragangliomas (PPGLs) by immunoassays compared with other methods. We aimed to compare the performance of a commercially available enzyme-linked immunoassay (EIA) kit with liquid chromatography-tandem mass spectrometric (LC-MS/MS) measurements of MNs to diagnose PPGLs. Methods: In a substudy of a prospective, multicenter trial to study the biochemical profiles of monoamine-producing tumors, we included 341 patients (174 males and 167 females) with suspected PPGLs (median age 54 years), of whom 54 had confirmed PPGLs. Plasma MNs were measured by EIA and LC-MS/MS, each in a specialized laboratory. Results: Plasma normetanephrine (NMN) and MN were measured 60 and 39% lower by EIA than by LC-MS/MS. Using upper cut-offs stipulated for the EIA, diagnostic sensitivity was only 74.1% at a specificity of 99.3%. In contrast, use of similar cut-offs for MN and overall lower age-adjusted cut-offs for NMN measured by LC-MS/MS returned a diagnostic sensitivity and specificity of 98.1 and 99.7%. Areas under receiver-operating characteristic curves, nevertheless, indicated comparable diagnostic performance of the EIA (0.993) and LC-MS/MS (0.985). Diagnostic sensitivity for the EIA increased to 96.2% with a minimal loss in specificity (95.1%) following use of cut-offs for the EIA adapted to correct for the negative bias. Conclusions: The EIA underestimates plasma MNs and diagnostic sensitivity is poor using commonly stipulated cut-offs, resulting in a high risk for missing patients with PPGLs. Correction of this shortcoming can be achieved by appropriately determined cut-offs resulting in comparable diagnostic performance of EIA and LC-MS/MS assays.

Accuracy of recommended sampling and assay methods for the determination of plasma-free and urinary fractionated metanephrines in the diagnosis of pheochromocytoma and paraganglioma: a systematic review

“…Key strengths are the number and quality of the included studies and the balanced distribution of the different test procedures between these studies. Important limitations are that only 2 studies used age-adjusted diagnostic cutoff levels for pMNs [10,11], and only 3 studies examined the effect of the additional measurement of MTY on test performance [9–11]. Results of the present analysis accordingly allow no conclusions with respect to the diagnostic benefit of these measures.…”

“…Simultaneous measurement of the 3-O-methylated metabolite of dopamine, methoxytyramine (MTY), has been advocated in particular for the diagnosis of P/PGL due to an underlying mutation of the succinate dehydrogenase B (SDHB) gene which is associated with an increased rate of metastatic disease [8]. However, the added value of MTY for identifying P/PGL in an unselected screening population is less clear [9,10], and in fact, the vast majority of studies on the diagnostic efficiency of pMNs or uMNs have not included MTY, apart from a few exceptions [9,11,10]. …”

Longitudinal plasma metanephrines preceding pheochromocytoma diagnosis: a retrospective case–control serum repository study

“…The DoDSR then sent the oldest, second-to-last, and most recent 0.5 ml samples prior to pheochromocytoma diagnosis along with matching control samples to Quest Diagnostics Nichols Institute (Chantilly, VA, USA) for measurement of PMN. PMN measurements were made by liquid chromatography and tandem mass spectrometry which is more accurate than enzyme immunoassay (EIA) (28). The upper limit of normal for metanephrine (MN) and normetanephrine (NMN) were 57 and 144 ng/ml respectively.…”

Blood sampling for metanephrines: to stick or stick and wait?

“…The same has already been established with the use of inappropriately high upper cut-offs of reference intervals for plasma metanephrines, where this leads to missed diagnoses in patients with pheochromocytoma or paraganglioma [2,10]. Thus, as outlined in the Endocrine Society guidelines [1], reference intervals for plasma-free metanephrines should be established for supine sampling conditions.…”

“…In essence, any preanalytical influence that reduces the difference in results of a diagnostic test between patients with and without disease will negatively impact the diagnostic performance of that test. While use of higher upper cut-offs established in populations with sampling in seated or non-fasting conditions -or as now outlined with venipuncture instead of an indwelling intravenous line -may certainly improve specificity and minimize numbers of false-positive results, the invariable result is also reduced diagnostic sensitivity and increased potential for missed diagnoses [2,10].…”