Chromogranin A as a diagnostic marker of pheochromocytoma and paraganglioma: A systematic review and meta-analysis.

OBJECTIVES: This work aims to assess the diagnostic value of chromogranin A (CgA) in the laboratory diagnosis of neuroendocrine tumors classified as pheochromocytoma and paraganglioma (PPGL). METHODS: A comprehensive search was performed in PubMed, Embase, the Cochrane Library, and Web of Science databases to obtain relevant studies reporting the diagnostic accuracy of CgA in patients with PPGL. The search involved studies written in English between the time of library inception and May 1, 2023. We computed the pooled sensitivity, specificity, and diagnostic odds ratio (DOR). Additionally, the receiver operating characteristic curve and area under the curve (AUC) were determined. The heterogeneity was assessed using the Chi-square test and the I2 test. The subgroup analyses were performed to investigate the origins of heterogeneity. Stata 15.1 statistical software was used in all data analyses. RESULTS: This meta-analysis included 13 studies involving 1470 patients. CgA had a pooled diagnostic sensitivity of 0.86 (95% CI 0.81-0.91), a specificity of 0.90 (95% CI 0.81-0.95), and a DOR of 57 (95% CI 23-142). CgA had an AUC of 0.93. The studies did not reveal any threshold effect (r = -0.165; p > 0.05). The subgroup analyses revealed that the control group category and the detection method caused the overall heterogeneity. CONCLUSIONS: Our study suggests that CgA is a helpful PPGL biomarker. However, relying solely on CgA for diagnosis is not advisable. A comprehensive approach is essential for accurate diagnosis. Future large-scale research is needed to refine CgA's clinical application.

Study of stability and interference for catecholamines and metanephrines, 3-methoxytyramine: key point of an accurate diagnosis for pheochromocytoma and paraganglioma.

BACKGROUND: Accurate diagnosis of pheochromocytoma and paraganglioma (PPGLs) is highly dependent on the detection of metanephrines and catecholamines. However, the systematic investigation on influencing factors including specimen (plasma or whole blood), anticoagulant, storage conditions, and interference factors need further confirmation. METHODS: Blood with heparin-lithium or EDTA-K2 were collected, stability of epinephrine (EPI), norepinephrine (NE), dopamine (DA), metanephrine (MN), normetanephrine (NMN), 3-methoxytyramine (3-MT) in whole blood and plasma at room temperature and 4 °C for different storage times, stability of plasma MN, NMN and 3-MT at -20 °C and -80 °C were investigated. Plasma with hemoglobin (1 g/L, 2 g/L, 3 g/L, 4 g/L, 6 g/L), TG (<5 mmol/L, 5-8 mmol/L, >8 mmol/L) were prepared. RESULTS: EPI, NE, DA were prone to degrade at room temperature, samples should be centrifuged at 4 °C. EPI and NE were stable in whole blood at 4 °C for 4 h and in plasma for 2 h. For MN, NMN, 3-MT, plasma can be stable at room temperature and 4 °C for at least 6 h, which is better than whole blood; there was no significant difference when stored at -20 °C and -80 °C for 7 days. Heparin-lithium had a slight advantage over EDTA-K2. EPI, NE, DA should not be performed when Hb > 1 g/L or TG > 5 mmol/L. MN, NMN, 3-MT should not be performed when Hb > 2 g/L, whereas TG had no interference. CONCLUSIONS: According to the actual clinical application scenario, this study provided a reliable basis for the accurate diagnosis of PPGLs.

Intrarenal hemodynamics and kidney function in pheochromocytoma and paraganglioma before and after surgical treatment.

PURPOSE: Current evidence regarding renal involvement in pheochromocytoma and paraganglioma (PPGL) is scant. More accurate diagnostic methods, such as renal Doppler ultrasound for intrarenal hemodynamic studies, may provide more detailed information on renal function. It might be postulated that renal function in PPGL patients might be altered by high blood pressure and excess secretion of catecholamines. The aim of this prospective study was to assess intrarenal blood flow parameters in PPGL patients included in the prospective monoamine-producing tumour (PMT) study and to evaluate the effects of normalisation of catecholamine production after surgical treatment on long-term renal function. MATERIALS AND METHODS: Seventy consecutive patients (aged 46.5 ± 14.0 years) with PPGL were included. Forty-eight patients from the PMT study cohort, matched for age, gender, blood pressure level and presence of hypertension, served as a control group. Renal artery doppler ultrasound spectral analysis included mean resistance index (RRI) and pulsatility index (PI). Forty-seven patients completed 12 months follow-up. RESULTS: There were no differences in renal parameters such as RRI, PI and kidney function between PPGL and non-PPGL patients as assessed by renal ultrasound, serum creatinine, eGFR and albumin excretion rate. No correlations between kidney function parameters, intrarenal doppler flow parameters and plasma catecholamines were observed in PPGL patients. At 12 months after surgery, no differences in creatinine level, eGFR, albumin excretion rate, RI and PI were found as compared to baseline results. CONCLUSIONS: In contrast to patients with other forms of secondary hypertension, our study did not show differences in intrarenal blood flow parameters and renal function between PPGL and non-PPGL subjects. Intrarenal hemodynamics and renal function did not change after normalisation of catecholamine levels by surgical treatment.

MicroRNA-210 May Be a Preoperative Biomarker of Malignant Pheochromocytomas and Paragangliomas.

BACKGROUND: Currently, no reliable predictive clinical or laboratory tests exist that can accurately distinguish between benign and malignant pheochromocytomas or paragangliomas (PPGLs). The aim of this study was to investigate if serum microRNA-210 (miR-210) levels could be a marker of malignancy in patients with PPGLs. METHODS: Preoperative serum from patients with PPGLs was collected on the day of surgery. Clinical demographics, germline mutation status, primary tumor size, postoperative biochemical response, and the development of malignant disease were prospectively collected. Total microRNA was extracted from preoperative serum samples, and miR-210 levels were measured by quantitative real-time reverse transcription-polymerase chain reaction and normalized to miR-16. Prognostic variables were compared using univariable and multivariable analyses. RESULTS: Of the 35 patients, 10 (29%) were diagnosed with malignant PPGLs and 25 patients (71%) were diagnosed with benign PPGLs (median follow-up 72.5 mo). Sixty-nine percent of patients had a pheochromocytoma (n = 24/35) compared with 31% of patients with paraganglioma (n = 11/35). The most common germline mutation was succinate dehydrogenase complex subunit B (SDHB) (n = 10). On univariable analysis, lower serum miR-210 expression level (2.3 ± 0.5 versus 3.1 ± 1.2, P = 0.013) and larger primary tumor size (6.7 ± 5.0 cm versus 4.1 ± 2.3 cm, P = 0.043) were significantly associated with malignant disease. No significant prognostic variables were found on multivariable analysis. CONCLUSIONS: In this pilot study, low serum miR-210 expression levels and large primary tumors were identified to be markers of PPGL malignancy on univariable analysis. Given the initial encouraging results in a small cohort, further investigation is warranted to determine if serum miR-210 levels are prognostic.

Biochemical Diagnosis of Chromaffin Cell Tumors in Patients at High and Low Risk of Disease: Plasma versus Urinary Free or Deconjugated O-Methylated Catecholamine Metabolites.

BACKGROUND: Measurements of plasma or urinary metanephrines are recommended for diagnosis of pheochromocytoma and paraganglioma (PPGL). What test offers optimal diagnostic accuracy for patients at high and low risk of disease, whether urinary free metanephrines offer advantages over deconjugated metanephrines, and what advantages are offered by including methoxytyramine in panels all remain unclear. METHODS: A population of 2056 patients with suspected PPGLs underwent prospective screening for disease using mass spectrometric-based measurements of plasma free, urinary deconjugated, and urinary free metanephrines and methoxytyramine. PPGLs were confirmed in 236 patients and were excluded in others on follow-up evaluation. RESULTS: Measurements of plasma free metabolites offered higher (P < 0.01) diagnostic sensitivity (97.9%) than urinary free (93.4%) and deconjugated (92.9%) metabolites at identical specificities for plasma and urinary free metabolites (94.2%) but at a lower (P < 0.005) specificity for deconjugated metabolites (92.1%). The addition of methoxytyramine offered little value for urinary panels but provided higher (P < 0.005) diagnostic performance for plasma measurements than either urinary panel according to areas under ROC curves (0.991 vs 0.972 and 0.964). Diagnostic performance of urinary and plasma tests was similar for patients at low risk of disease, whereas plasma measurements were superior to both urinary panels for high-risk patients. CONCLUSIONS: Diagnosis of PPGLs using plasma or urinary free metabolites provides advantages of fewer false-positive results compared with commonly measured deconjugated metabolites. The plasma panel offers better diagnostic performance than either urinary panel for patients at high risk of disease and, with appropriate preanalytics, provides the test of choice. Measurements of methoxytyramine in urine show limited diagnostic utility compared with plasma.

ACCURACY OF PLASMA FREE METANEPHRINES IN THE DIAGNOSIS OF PHEOCHROMOCYTOMA AND PARAGANGLIOMA: A SYSTEMATIC REVIEW AND META-ANALYSIS.

OBJECTIVE: Various studies have validated plasma free metanephrines (MNs) as biomarkers for pheochromocytoma and paraganglioma (PPGL). This meta-analysis aimed to estimate the overall diagnostic accuracy of this biochemical test for PPGL. METHODS: We searched the PubMed, the Cochrane Library, Web of Science, Embase, Scopus, OvidSP, and ProQuest Dissertations & Theses databases from January 1, 1995 to December 2, 2016 and selected studies written in English that assessed plasma free MNs in the diagnosis of PPGL. Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) was used to evaluate the quality of the included studies. We calculated pooled sensitivities, specificities, positive and negative likelihood ratios, diagnostic odds ratios (DORs) and areas under curve (AUCs) with their 95% confidence intervals (95% CIs). Heterogeneity was assessed by I2. To identify the source of heterogeneity, we evaluated the threshold effect and performed a meta-regression. Deeks' funnel plot was selected for investigating any potential publication bias. RESULTS: Although the combination of metanephrine (MN) and normetanephrine (NMN) carried lower specificity (0.94, 95% CI 0.90-0.97) than NMN (0.97, 95% CI 0.92-0.99), NMN was generally more accurate than individual tests, with the highest AUC (0.99, 95% CI 0.97-0.99), DOR (443.35, 95% CI 216.9-906.23), and pooled sensitivity (0.97, 95% CI 0.94-0.98) values. Threshold effect and meta-regression analyses showed that different cut-offs, blood sampling positions, study types and test methods contributed to heterogeneity. CONCLUSION: This meta-analysis suggested an effective value for combined plasma free MNs for the diagnosis of PPGL, but testing for MNs requires more standardization using tightly regulated studies. ABBREVIATIONS: AUC = area under curve; CI = confidence interval; DOR = diagnostic odds ratio; EIA = enzyme immunoassay; LC-ECD = liquid chromatography-electrochemical detection; LC-MS/MS = liquid chromatography-tandem mass spectrometry; MN = metanephrine; NMN = normetaneprhine; PPGL = pheochromocytoma and paraganglioma; QUADAS-2 = Quality Assessment of Diagnostic Accuracy Studies 2.

Dopamine concentration in blood platelets is elevated in patients with head and neck paragangliomas.

BACKGROUND: Plasma 3-methoxytyramine (3-MT), a metabolite of dopamine, is elevated in up to 28% of patients with head and neck paragangliomas (HNPGLs). As free dopamine is incorporated in circulating platelets, we determined dopamine concentration in platelets in patients with a HNPGL. METHODS: A single center cohort study was performed between 2012 and 2014. Thirty-six patients with a HNPGL were compared to healthy controls (68 for dopamine in platelets and 120 for plasma 3-MT). RESULTS: Dopamine concentration in platelets was elevated in HNPGL patients compared to healthy controls (median [interquartile ranges] 0.48 [0.32-0.82] pmol/109 platelets vs. 0.31 [0.24-0.47] pmol/109 platelets; p<0.05), whereas plasma 3-MT concentration did not differ between both groups (0.06 [0.06-0.08] nmol/L vs. 0.06 [0.06-0.06] nmol/L; p=0.119). Based on 68 healthy controls, the reference interval for dopamine concentration in platelets was 0.12-0.97 pmol/109 platelets. Six (16.7%) patients with a HNPGL demonstrated an increased dopamine concentration in platelets compared to three (8.3%) patients with an increased plasma 3-MT level (p=0.053). The sensitivity and specificity were 16.7% and 98.5% for platelet dopamine and 8.3% and 97.5% for plasma 3-MT concentration (p=0.37). CONCLUSIONS: Dopamine concentration in platelets is elevated in patients with a HNPGL compared to healthy subjects, and may be a novel biomarker for dopamine producing paraganglioma.

Somatic HIF2A gain-of-function mutations in paraganglioma with polycythemia.

Hypoxia-inducible factors are transcription factors controlling energy, iron metabolism, erythropoiesis, and development. When these proteins are dysregulated, they contribute to tumorigenesis and cancer progression. However, mutations in genes encoding α subunits of hypoxia-inducible factors (HIF-α) have not previously been identified in any cancer. Here we report two novel somatic gain-of-function mutations in the gene encoding hypoxia-inducible factor 2α (HIF2A) in two patients, one presenting with paraganglioma and the other with paraganglioma and somatostatinoma, both of whom had polycythemia. The two mutations were associated with increased HIF-2α activity and increased protein half-life.

Diagnosing phaeochromocytoma/paraganglioma in a patient presenting with critical illness: biochemistry versus imaging.

Phaeochromocytomas and paragangliomas (PPGLs) are revealed by acute cardiovascular complications involving end-organ damage in up to 20% of cases, a presentation associated with particularly high risk for mortality. Among such cases, PPGLs should be considered in patients with unexplained left ventricular failure, multi-organ failure, hypertensive crises or shock. The diagnosis of PPGL commonly relies on measurements of metanephrines in plasma or urine. However, acute critical illness is usually associated with sympathoadrenal activation. Thus, levels of metanephrines in patients in an acute emergency or intensive care setting, whether treated or not with vasoactive drugs, usually cannot be used to reliably diagnose PPGL. Delays in provision of diagnostic test results, particularly when these require 24-h urine collections, may also be incompatible for any need for rapid decisions on patient management or therapeutic interventions. The acute emergency situation therefore represents one exception to the rule where imaging studies to search for a PPGL may be undertaken without biochemical evidence of a catecholamine-producing tumour.

Laboratory evaluation of pheochromocytoma and paraganglioma.

BACKGROUND: Pheochromocytomas and paragangliomas (PPGLs) are potentially lethal yet usually surgically curable causes of endocrine hypertension; therefore, once clinical suspicion is aroused it is imperative that clinicians choose the most appropriate laboratory tests to identify the tumors. CONTENT: Compelling evidence now indicates that initial screening for PPGLs should include measurements of plasma free metanephrines or urine fractionated metanephrines. LC-MS/MS offers numerous advantages over other analytical methods and is the method of choice when measurements include methoxytyramine, the O-methylated metabolite of dopamine. The plasma test offers advantages over the urine test, although it is rarely implemented correctly, rendering the urine test preferable for mainstream use. To ensure optimum diagnostic sensitivity for the plasma test, reference intervals must be established for blood samples collected after 30 min of supine rest and after an overnight fast when measurements include methoxytyramine. Similarly collected blood samples during screening, together with use of age-adjusted reference intervals, further minimize false-positive results. Extents and patterns of increases in plasma normetanephrine, metanephrine, and methoxytyramine can additionally help predict size and adrenal vs extraadrenal locations of tumors, as well as presence of metastases and underlying germline mutations of tumor susceptibility genes. SUMMARY: Carried out correctly at specialist endocrine centers, collection of blood for measurements of plasma normetanephrine, metanephrine, and methoxytyramine not only provides high accuracy for diagnosis of PPGLs, but can also guide clinical decision-making about follow-up imaging strategies, genetic testing, and therapeutic options. At other centers, measurements of urine fractionated metanephrines will identify most PPGLs.

Radioimmunoassay of free plasma metanephrines for the diagnosis of catecholamine-producing tumors.

BACKGROUND: The determination of plasma metanephrines (MNs) provides a highly sensitive test for the diagnosis of catecholamine producing tumors. Chromatographic determinations with electrochemical or mass spectrometric detections are the methods of choice, but immunological assays have been developed. This study evaluated the clinical performances of a radioimmunoassay for free MNs in plasma. METHODS: MNs, normetanephrine (NMN) and metanephrine (MN) and catecholamines, norepinephrine (NE) and epinephrine (E) were determined in plasma and urine of 533 patients suspected of catecholamine producing tumor. Urinary and plasma catecholamines and urinary MNs were determined by HPLC using amperometric detection. Plasma MNs were purified by solid phase chromatography and quantified by a specific radioimmunoassay. RESULTS: Fifty-nine patients had tumors (13 paraganglioma and 46 pheochromocytoma) and the diagnosis was excluded in 474 patients. Receiver operator characteristic curves have identified optimal thresholds at 100 pg/mL for plasma NMN (sensitivity 96.6% and specificity 95.8%) and 70 pg/mL for plasma MN (sensitivity 61.0% and specificity 96.8%). These cut-off values were lower than those suggested by the manufacturer (170 and 100 pg/mL, respectively). The sensitivity of combined MNs was similar in plasma (100%) and urine (98%) but higher than that of urinary catecholamines (85%, p<0.001). The specificity of combined MNs in plasma (95%) was higher than urinary MNs (85%, p<0.001) and plasma catecholamines (75%, p<0.001). CONCLUSIONS: Plasma-free and urinary-total MNs have a better discriminative power than catecholamines in the diagnosis of catecholamines producing tumors. Using these established cut-offs, measurement of plasma-free MN by radioimmunoassay represents an effective alternative to chromatographic methods.

Plasma chromogranin A levels are increased in a small portion of patients with hereditary head and neck paragangliomas.

CONTEXT: The majority of patients with head and neck paragangliomas (HNPGL) have biochemically silent tumours. Chromogranin A (CgA) is a tumour marker for neuroendocrine tumours. OBJECTIVE: To assess the role of CgA as a tumour marker in patients with hereditary HNPGL. PATIENTS AND METHODS: We included 95 consecutive patients with hereditary HNPGL for screening of plasma CgA levels and catecholamine excess by measurement of 24-h urinary excretion of (nor)metanephrine, (nor)adrenaline, VMA, dopamine and 3-methoxytyramine. In all patients with catecholamine excess, abdominal/intrathoracic paragangliomas were excluded by (123) I-MIBG scintigraphy, MRI and/or CT. RESULTS: Plasma CgA levels were increased in only 15 of 95 patients (16%). Thirty-three of the 95 patients (35%) had increased urinary excretion rates of catecholamines. Six of these 33 patients (18%) had increased plasma CgA levels. Nine of the 62 patients (15%) with a biochemically silent tumour, i.e. no increased urinary excretion of catecholamines or their metabolites, had increased CgA levels. Increased plasma CgA levels were positively correlated with urinary excretion rates of noradrenaline (r = 0·68, P = 0·005) and normetanephrine (r = 0·68, P = 0·005). There was a positive correlation between maximal HNPGL diameter and plasma CgA levels in the 57 patients with a single HNPGL (r = 0·57, P = 0·001). CONCLUSIONS: Plasma CgA levels are increased in only a small portion of patients with hereditary HNPGL and have limited additional value to the combination of radiological and routine biochemical assessment of patients with HNPGL. Increased plasma CgA levels are associated with increased noradrenergic activity and tumour size in patients with a single HNPGL.

Comparison of plasma metanephrines measured by a commercial immunoassay and urinary catecholamines in the diagnosis of pheochromocytoma.

BACKGROUND: The diagnosis of pheochromocytomas requires consideration among patients suffering from hypertension, unexplained spells, incidental adrenal masses, or a family history of pheochromocytoma. Accordingly, the diagnosis requires a biochemical test with high sensitivity and specificity. AIM: To compare plasma free metanephrines as measured by a commercial immunoassay and the 24-hour urinary excretion of catecholamines. METHOD: Plasma free metanephrines were measured in 185 patients suspected of pheochromocytoma. Concomitant measurements of urinary catecholamines were performed in 115 patients. Based on clinical findings, imaging and biochemistry 11 cases were found; 9 were diagnosed with pheochromocytoma, one patient with paraganglioma and one patient with ganglioneuroma. RESULTS: All patients with pheochromocytoma/paraganglioma had abnormally elevated concentrations of either plasma metanephrine or normetanephrine. The patient with ganglioneuroma had normal plasma metanephrine levels, corresponding to a sensitivity of 91%. In two patients where pheochromocytoma was excluded, plasma metanephrin or normetanephrine was above the reference level, corresponding to a specificity of 99%. Urinary catecholamines were determined in 10 of 11 patients with a positive diagnosis, and all 10 showed elevated levels of either urinary epinephrine or norepinephrine, including the patient with ganglioneuroma (equivalent to a sensitivity of 100%). Seven patients, in whom pheochromocytoma was excluded, had elevated urinary catecholamines (equivalent to a specificity of 94%). CONCLUSION: Measurement of plasma free metanephrines by immunoassay appears to be a useful diagnostic test in patients suspected of pheochromocytoma, with a high specificity as compared with urinary catecholamines. The latter may result in fewer false-positive findings, an outcome which may be particularly troublesome.

Optimized procedures for testing plasma metanephrines in patients on hemodialysis.

Diagnosis of pheochromocytomas and paragangliomas in patients receiving hemodialysis is troublesome. The aim of the study was to establish optimal conditions for blood sampling for mass spectrometric measurements of normetanephrine, metanephrine and 3-methoxytyramine in patients on hemodialysis and specific reference intervals for plasma metanephrines under the most optimal sampling conditions. Blood was sampled before and near the end of dialysis, including different sampling sites in 170 patients on hemodialysis. Plasma normetanephrine concentrations were lower (P < 0.0001) and metanephrine concentrations higher (P < 0.0001) in shunt than in venous blood, with no differences for 3-methoxytyramine. Normetanephrine, metanephrine and 3-methoxytyramine concentrations in shunt and venous blood were lower (P < 0.0001) near the end than before hemodialysis. Upper cut-offs for normetanephrine were 34% lower when the blood was drawn from the shunt and near the end of hemodialysis compared to blood drawn before hemodialysis. This study establishes optimal sampling conditions using blood from the dialysis shunt near the end of hemodialysis with optimal reference intervals for plasma metanephrines for the diagnosis of pheochromocytomas/paragangliomas among patients on hemodialysis.

Plasma Metabolome Profiling for the Diagnosis of Catecholamine Producing Tumors.

Context: Pheochromocytomas and paragangliomas (PPGL) cause catecholamine excess leading to a characteristic clinical phenotype. Intra-individual changes at metabolome level have been described after surgical PPGL removal. The value of metabolomics for the diagnosis of PPGL has not been studied yet. Objective: Evaluation of quantitative metabolomics as a diagnostic tool for PPGL. Design: Targeted metabolomics by liquid chromatography-tandem mass spectrometry of plasma specimens and statistical modeling using ML-based feature selection approaches in a clinically well characterized cohort study. Patients: Prospectively enrolled patients (n=36, 17 female) from the Prospective Monoamine-producing Tumor Study (PMT) with hormonally active PPGL and 36 matched controls in whom PPGL was rigorously excluded. Results: Among 188 measured metabolites, only without considering false discovery rate, 4 exhibited statistically significant differences between patients with PPGL and controls (histidine p=0.004, threonine p=0.008, lyso PC a C28:0 p=0.044, sum of hexoses p=0.018). Weak, but significant correlations for histidine, threonine and lyso PC a C28:0 with total urine catecholamine levels were identified. Only the sum of hexoses (reflecting glucose) showed significant correlations with plasma metanephrines.By using ML-based feature selection approaches, we identified diagnostic signatures which all exhibited low accuracy and sensitivity. The best predictive value (sensitivity 87.5%, accuracy 67.3%) was obtained by using Gradient Boosting Machine Modelling. Conclusions: The diabetogenic effect of catecholamine excess dominates the plasma metabolome in PPGL patients. While curative surgery for PPGL led to normalization of catecholamine-induced alterations of metabolomics in individual patients, plasma metabolomics are not useful for diagnostic purposes, most likely due to inter-individual variability.

A 3-min UPLC-MS/MS method for the simultaneous determination of plasma catecholamines and their metabolites: Method verification and diagnostic efficiency.

OBJECTIVE: To verify a rapid and sensitive ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the quantification of catecholamines and their metabolites, and to validate its efficiency for the diagnosis of phaeochromocytomas and paragangliomas (PPGLs). METHODS: Plasma samples were pretreated with solid-phase extraction, followed by a 3-min UPLC-MS/MS analysis to quantify epinephrine (E), norepinephrine (NE), dopamine (DA), metanephrine (MN), normetanephrine (NMN) and 3-methoxytyramine (3-MT), simultaneously. The UPLC-MS/MS method was comprehensively verified and its diagnostic efficiency on PPGLs was tested using 7 PPGLs and 408 non-PPGLs patient plasma samples. RESULTS: Using the developed method, the limit of detections (LODs) of the 6 analytes ranged from 0.0002 nmol/L (MN) to 0.0250 nmol/L (NE), while the lower limit of measuring intervals (LLMIs) ranged from 0.05 nmol/L (E, MN and NMN) to 0.10 nmol/L (NE and DA). The reportable ranges were 0.05-30.00 nmol/L for E, MN and NMN, 0.10-30.00 nmol/L for NE and DA, 1.00-300.00 pg/mL for 3-MT. No significant matrix effect was detected after correcting using internal standard. Besides, intra-day and inter-day precision were also within acceptance criteria with coefficient of variations (CVs) ≤ 15% and recoveries ranged from 95% to 115% for all the 6 analytes. The carryover effect was lower than 10%. Its diagnostic efficiency for PPGLs was significantly increased, the areas under the receiver operating characteristic (ROC) curves were increased from 68.7% to 89.1% (using E, NE and DA) to 75.2%-99.9% (using MN, NMN and 3-MT). CONCLUSION: This study verified a rapid UPLC-MS/MS method for the determination of catecholamines and their metabolites in human plasma. It showed high diagnostic efficiency and will serve as an important tool to avoid the risk for missing patients with PPGLs.

Properly Collected Plasma Metanephrines Excludes PPGL After False-Positive Screening Tests.

CONTEXT: False-positive results are common for pheochromocytoma/paraganglioma (PPGL) real-world screening. OBJECTIVE: Determine the correlation between screening urine and seated plasma metanephrines in outpatients where PPGL was absent, compared to meticulously prepared and supine-collected plasma metanephrines with age-adjusted references. DESIGN: Retrospective cohort study. SETTING: Databases from a single-provider provincial laboratory (2012-2018), a validated PPGL registry, and a manual chart review from a specialized endocrine testing unit. PATIENTS: PPGL registry data excluded known PPGL cases from the laboratory database. Outpatients having both urine and plasma metanephrines <90 days apart. METHODS: The correlation between urine and seated plasma measures along with the total positivity rate. All cases of plasma metanephrines drawn in the endocrine unit were reviewed for test indication and test positivity rate. RESULTS: There were 810 non-PPGL pairs of urine and plasma metanephrines in the laboratory database; 46.1% of urine metanephrines were reported high. Of seated outpatient plasma metanephrines drawn a median of 5.9 days later, 19.2% were also high (r = 0.33 and 0.50 for normetanephrine and metanephrine, respectively). In contrast, the meticulously prepared and supine collected patients (n = 139, 51% prior high urine metanephrines) had <3% rate of abnormal high results in patients without known PPGL/adrenal mass. CONCLUSIONS: There was a poor-to-moderate correlation between urine and seated plasma metanephrines. Up to 20% of those with high urine measures also had high seated plasma metanephrines in the absence of PPGL. Properly prepared and collected supine plasma metanephrines had a false-positive rate of <3% in the absence of known PPGL/adrenal mass.