A UK national audit of the laboratory investigation of phaeochromocytoma and paraganglioma

BACKGROUND

Phaeochromocytomas and paragangliomas (PPGL) are catecholamine secreting tumours associated with significant morbidity and mortality. Timely diagnosis and management are essential. A range of laboratory tests can be utilised in the investigation of PPGL. There is scope for significant variation in practice between centres. We aimed to investigate how the laboratory investigation of PPGL is performed in laboratories across the United Kingdom.

METHODS

A questionnaire consisting of 21 questions was circulated to Clinical Biochemistry laboratories in the United Kingdom via the Association for Clinical Biochemistry and Laboratory Medicine office. The survey was designed to allow audit against Endocrine Society Guidelines on the Investigation and Management of PPGL and to obtain information on other important aspects not included in these guidelines.

RESULTS

Responses were received from 58 laboratories and the data were compiled. The majority of laboratories use either urine or plasma metanephrines in first-line testing for PPGL, although a number of different combinations of biochemistry tests are utilised in different centres. All laboratories measuring metanephrines or catecholamines in-house use LC or LC-MS/MS methods. There are some marked differences between laboratories in urine metanephrines reference ranges used and sample requirements.

CONCLUSIONS

There is evidence of good practice in UK laboratories (as assessed against Endocrine Society Guidelines) such as widespread use of urine/plasma metanephrines and appropriate analytical methodologies used. However, there is also evidence of variations in practice in some areas that should be addressed.

Dilute, derivatise and shoot: Measurement of urinary free metanephrines and catecholamines as ethyl derivatives by LC-MSMS

Background

The measurement of catecholamines and their metabolites in either urine or plasma is an important diagnostic test used to exclude the presence of neuroendocrine tumours. Because of weak chromatographic retention and potential ion-suppression, reverse-phase LC-MSMS is not ideal for analysis of these polar molecules. Here, we investigate derivatisation by ethylation as an alternative approach.

Methods

A simple and rapid method involving acetaldehyde and a reducing agent was used to convert urine free metanephrines and catecholamines, and their deuterated analogues as internal standards, to mono-ethyl or diethyl- derivatives. Using an Agilent 6460 triple-quadrupole mass spectrometer, precursor and product ion mass spectra were recorded to allow comparison of multiple reaction monitoring methods for both derivatised and non-derivatised analytes under reverse-phase LC-MSMS conditions with positive electrospray ionization.

Results

Conversion of biogenic amines to less polar ethyl derivatives increased their mass and enhanced the intensity of their molecular ions and fragments. Ethylation also improved the chromatographic properties of the amines, with greater retention and elution from reverse-phase HPLC columns with a methanol or acetonitrile gradient. The signal response of tandem mass spectrometric detection was increased up to 50-fold for ethyl metanephrines compared to non-derivatised compounds. This increase allowed for the omission of solid-phase extraction of urine as a clean-up step prior to analysis. The 'dilute-derivatise-shoot' method maintained analytical performance with respect to between-run imprecision (CV < 6%) and accuracy in an external quality assurance program. Gender-related ranges for free metanephrines in early-morning spot urines, collected from adult patients, were similar using either derivatised or non-derivatised samples.

Conclusions

The LC-MSMS detection of free urine biogenic amines can be greatly enhanced by ethyl derivatisation, which is easy and rapid to perform. Advantages include improved chromatography and lower limits of quantitation, that negate the requirement for solid-phase clean-up of urine prior to analysis. A disadvantage is the potential toxicity of the derivatising agents used if they are not handled appropriately.

Hypertension: The role of biochemistry in the diagnosis and management

Hypertension is defined as a persistently elevated blood pressure ≥140/90mmHg. It is an important treatable risk factor for cardiovascular disease, with a high prevalence in the general population. The most common cause, essential hypertension, is a widespread disease - however, secondary hypertension is under investigated and under diagnosed. Collectively, hypertension is referred to as a "silent killer" - frequently it displays no overt symptomatology. It is a leading risk factor for death and disability globally, with >40% of persons aged over 25 having hypertension. A vast spectrum of conditions result in hypertension spanning essential through resistant, to patients with an overt endocrine cause. A significant number of patients with hypertension have multiple cardiovascular risk factors at the time of presentation. Both routine and specialised biochemical investigations are paramount for the evaluation of these patients and their subsequent management. Biochemical testing serves to identify those hypertensive individuals who are at higher risk on the basis of evidence of dysglycaemia, dyslipidaemia, renal impairment, or target organ damage and to exclude identifiable causes of hypertension. The main target of biochemical testing is the identification of patients with a specific and treatable aetiology of hypertension. Information gleaned from biochemical investigation is used to risk stratify patients and tailor the type and intensity of subsequent management and treatment. We review the approach to the biochemical investigation of patients presenting with hypertension and propose a diagnostic algorithm for work-up.

Single-centre study of the diagnostic performance of plasma metanephrines with seated sampling for the diagnosis of phaeochromocytoma/paraganglioma

Background

Measurement of plasma metanephrines is regarded as one of the best screening tests for phaeochromocytoma/paraganglioma. Current guidelines recommend that samples are ideally collected in the supine position after 30 min rest and interpreted using supine reference ranges, in order to optimize the diagnostic performance of the test. Current practice in our centre is to collect samples for plasma metanephrines from seated patients. The aim of the study was to determine, if seated sampling for plasma metanephrines provides acceptable diagnostic performance in our centre.

Methods

Clinical and laboratory data of 113 patients, gathered over a four-year period 2010–2014, were reviewed. All had undergone preoperative plasma metanephrines measurement and had postoperative histopathology confirmation or exclusion of phaeochromocytoma/paraganglioma.

Results

Of 113 patients included in the study, 40 had a histological diagnosis of phaeochromocytoma/paraganglioma. The remaining 73 patients had an alternative adrenal pathology. The diagnostic sensitivity of normetanephrine or metanephrine above the upper limit of our in-house seated reference range was 93%. However, excluding three cases of paraganglioma determined clinically and biochemically to be non-functional raised the sensitivity to 100%. Diagnostic specificity was 90%. Applying published supine reference ranges made no difference to diagnostic sensitivity in this group of patients but decreased diagnostic specificity to 75%.

Conclusions

While these data are derived from a relatively small study population, they demonstrate acceptable diagnostic performance for seated plasma metanephrines as a screening test for phaeochromocytoma/paraganglioma. These data highlight a high diagnostic sensitivity for plasma metanephrines with seated sampling in our centre.

Multiple Reaction Monitoring with Multistage Fragmentation (MRM3) Detection Enhances Selectivity for LC-MS/MS Analysis of Plasma Free Metanephrines

BACKGROUND

LC-MS/MS with multiple reaction monitoring (MRM) is a powerful tool for quantifying target analytes in complex matrices. However, the technique lacks selectivity when plasma free metanephrines are measured. We propose the use of multistage fragmentation (MRM3) to improve the analytical selectivity of plasma free metanephrine measurement.

METHODS

Metanephrines were extracted from plasma with weak cation exchange solid-phase extraction before separation by hydrophilic interaction liquid chromatography. We quantified normetanephrine and metanephrine by either MRM or MRM3 transitions m/z 166→134→79 and m/z 180→149→121, respectively.

RESULTS

Over a 6-month period, approximately 1% (n = 21) of patient samples showed uncharacterized coeluting substances that interfered with the routine assay, resulting in an inability to report results. Quantification with MRM3 removed these interferences and enabled measurement of the target compounds. For patient samples unaffected by interferences, Deming regression analysis demonstrated a correlation between MRM3 and MRM methods of y = 1.00x − 0.00 nmol/L for normetanephrine and y = 0.99x + 0.03 nmol/L for metanephrine. Between the MRM3 method and the median of all LC-MS/MS laboratories enrolled in a quality assurance program, the correlations were y = 0.97x + 0.03 nmol/L for normetanephrine and y = 1.03x − 0.04 nmol/L for metanephrine. Imprecision for the MRM3 method was 6.2%–7.0% for normetanephrine and 6.1%–9.9% for metanephrine (n = 10). The lower limits of quantification for the MRM3 method were 0.20 nmol/L for normetanephrine and 0.16 nmol/L for metanephrine.

CONCLUSIONS

The use of MRM3 technology improves the analytical selectivity of plasma free metanephrine quantification by LC-MS/MS while demonstrating sufficient analytical sensitivity and imprecision.

Determination of catecholamines in plasma and urine

For more than 20 years, measurement of catecholamines in plasma and urine in clinical chemistry laboratories has been the cornerstone of the diagnosis of neuroendocrine tumors deriving from the neural crest such as pheochromocytoma (PHEO) and neuroblastoma (NB), and is still used to assess sympathetic stress function in man and animals. Although assay of catecholamines in urine are still considered the biochemical standard for the diagnosis of NB, they have been progressively abandoned for excluding/confirming PHEOs to the advantage of metanephrines (MNs). Nevertheless, catecholamine determinations are still of interest to improve the biochemical diagnosis of PHEO in difficult cases that usually require a clonidine-suppression test, or to establish whether a patient with PHEO secretes high concentrations of catecholamines in addition to metanephrines. The aim of this chapter is to provide an update about the catecholamine assays in plasma and urine and to show the most common pre-analytical and analytical pitfalls associated with their determination.

Consideration of the degree of increase in urine metadrenalines provides superior specificity in the diagnosis of phaeochromocytoma than additional urine catecholamine measurement

Background

Measurement of fractionated plasma or urine metadrenalines is the recommended screening test in the diagnosis of phaeochromocytoma, with clinical cut-offs geared towards diagnostic sensitivity. Current practice at Salford Royal Hospital is to add urine catecholamines onto samples with raised urine metadrenalines, with the aim of adding specificity to a diagnosis of phaeochromocytoma.

Methods

This practice was reviewed by identifying a series of patients with raised urine metadrenalines who had catecholamines reflectively added. A total of 358 samples were identified from 242 patients, of which 228 had urine catecholamines measured.

Results

A diagnosis of ‘phaeochromocytoma‘ (n = 41) or ‘no phaeochromocytoma‘ (n = 90) was obtained in 131 of 228 patients, giving raised urine metadrenalines a positive predictive value for phaeochromocytoma of 31%. The finding of increased urine catecholamines in samples with raised urine metadrenalines increased specificity for phaeochromocytoma to 70%. However, 95% diagnostic specificity for phaeochromocytoma could be achieved by the introduction of a second cut-off for urine metadrenalines geared towards maximizing specificity.

Conclusions

Consideration of the degree of increase in urine metadrenalines is a superior method of determining the likelihood of phaeochromocytoma than measurement of urine catecholamines.

Reference intervals for plasma free metanephrines with an age adjustment for normetanephrine for optimized laboratory testing of phaeochromocytoma

BACKGROUND

Measurements of plasma normetanephrine and metanephrine provide a useful diagnostic test for phaeochromocytoma, but this depends on appropriate reference intervals. Upper cut-offs set too high compromise diagnostic sensitivity, whereas set too low, false-positives are a problem. This study aimed to establish optimal reference intervals for plasma normetanephrine and metanephrine.

METHODS

Blood samples were collected in the supine position from 1226 subjects, aged 5-84 y, including 116 children, 575 normotensive and hypertensive adults and 535 patients in whom phaeochromocytoma was ruled out. Reference intervals were examined according to age and gender. Various models were examined to optimize upper cut-offs according to estimates of diagnostic sensitivity and specificity in a separate validation group of 3888 patients tested for phaeochromocytoma, including 558 with confirmed disease.

RESULTS

Plasma metanephrine, but not normetanephrine, was higher (P < 0.001) in men than in women, but reference intervals did not differ. Age showed a positive relationship (P < 0.0001) with plasma normetanephrine and a weaker relationship (P = 0.021) with metanephrine. Upper cut-offs of reference intervals for normetanephrine increased from 0.47 nmol/L in children to 1.05 nmol/L in subjects over 60 y. A curvilinear model for age-adjusted compared with fixed upper cut-offs for normetanephrine, together with a higher cut-off for metanephrine (0.45 versus 0.32 nmol/L), resulted in a substantial gain in diagnostic specificity from 88.3% to 96.0% with minimal loss in diagnostic sensitivity from 93.9% to 93.6%.

CONCLUSIONS

These data establish age-adjusted cut-offs of reference intervals for plasma normetanephrine and optimized cut-offs for metanephrine useful for minimizing false-positive results.

Urinary free (unconjugated) metadrenalines in different hereditary forms of catecholamine-secreting phaeochromocytoma/paraganglioma

Background

Catecholamine-producing neuroendocrine tumours are found in chromaffin cells of the adrenal medulla (phaeochromocytoma) or extra-adrenal paraganglia (paraganglioma), known collectively as PPGLs. In approximately a quarter or more of cases of PPGL, these rare tumours arise as a result of germline mutations of several tumour susceptibility genes. At the Crosshouse laboratory, urine tests include free metadrenalines (fMAs) (also known as free metanephrines) which demonstrate superior sensitivity over that obtained by urinary vanillyl mandelic acid, catecholamines or plasma catecholamines in the diagnosis of PPGL. This retrospective audit was to determine if urinary fMAs offered discrimination among the hereditary forms of PPGL.

Methods

Retrospective biochemical and genetic data were gathered from 1997 to 2011. The identified urine specimens were those obtained at the time of first diagnosis or recurrence of PPGL. Results of catecholamines and metabolites were standardized as multiples of their respective relevant upper reference limits (URLs).

Results

Results were available for 29 affected patients (15 females and 14 males), median age 26 (range 9–63) years, comprising three mutation groups: succinate dehydrogenase subunit B or D ([SDHB/D] 16 patients), multiple endocrine neoplasia type 2 ([MEN 2] 6 patients) and von Hippel–Lindau disease ([VHL] 7 patients). The parent catecholamines exhibited increased values for noradrenaline (NA) and/or adrenaline (AD) for 25/29 (86.2%) patients. Either or both free normetadrenaline (fNMA) and fMA were elevated in 29/29 (100%) patients.

Conclusions

The ratio of the multiples of URL for fMA/fNMA displayed a clearer separation of MEN 2 patients from those with SDHB/D or VHL than did the equivalent AD/NA ratio.

Improved plasma free metadrenaline analysis requires mixed mode cation exchange solid-phase extraction prior to liquid chromatography tandem mass spectrometry detection

Background

The investigation and effective management of phaeochromocytoma involves biochemical measurement of either conjugated total urine or plasma free metadrenalines. Current analytical methods include enzyme-linked immunosorbent assays, high-performance liquid chromatography (HPLC) with electrochemical detection (ECD) or liquid chromatography tandem mass spectrometry (LCMS/MS). Since the first two methods are either extremely laborious, necessitate low sample run numbers, result in slow turnaround times or are subject to analytical interference, a robust, routine clinical method is not achievable. We established a novel sample preparation method to measure plasma free metadrenalines using LCMS/MS.

Methods

Three different solid-phase extraction (SPE) methods were compared: hydrophilic–lipophilic balance sorbent (HLB), weak cation exchange (WCX) and mixed mode cation exchange (MCX) and their ability to remove interfering compounds prior to LCMS/MS analysis. Maximum recovery of plasma free metadrenaline and plasma free normetadrenaline were achieved by positively charging compounds prior to SPE application.

Results

Compared with HLB and WCX cartridges, MCX extraction resulted in chromatography without co-eluting interference with superior assay precision and accuracy. Additionally, samples that could not be quantified because of interference using HPLC/ECD could be readily assayed using this new method.

Conclusions

The use of the MCX SPE method with LCMS/MS detection provides an improved assay to measure plasma free metadrenalines in comparison to many available alternative methods.

Pediatric endocrine screening for von Hippel-Lindau disease: benefits and the challenge of compliance

Fifteen children and adolescents (4 male) with a median age of 5.4 yr (range 1.2 -13.6 yr) were entered into a screening protocol to identify lesions of von Hippel-Lindau (VHL) disease. Fourteen had an affected first-degree relative and one had a previous VHL lesion. Screening during the period of 2000 to 2008 followed published guidelines and consisted of measurement of urinary catecholamines, adrenal and renal imaging and ophthalmological and central nervous system examinations and imaging. Screening identified 8 VHL lesions in 6 asymptomatic patients with confirmed genetic mutations. Five patients had elevated urinary noradrenaline excretion and in each case the presence of a pheochromocytoma was identified on adrenal magnetic resonance imagin scan. In one patient a left-sided tumor was identified 1 yr after a right-sided tumor had been removed. In a sixth patient a retinal capillary hemangioma and a cerebellar hemangioblastoma were identified. Patient compliance with the screening protocol was variable reflecting its time-intensive nature. A formal screening programme for this at-risk population of pediatric patients, despite being intensive, can identify VHL lesions during a pre-morbid phase and may thus have a beneficial impact on prognosis in this serious disorder.

An audit of management of patients with borderline increased plasma-free metanephrines

Background

Measurement of plasma-free metanephrine plus normetanephrine (PFM) is the best screening test for phaeochromocytoma. While clearly raised levels are diagnostic, borderline increases may be associated with factors such as stress and medications, and should prompt a repeat study after interfering factors are withdrawn.

Methods

PFM results reported by a teaching hospital laboratory over a 12-month period were extracted from the laboratory information system. All borderline raised results were examined for a subsequent repeat test (as recommended by attached interpretative comment) and those not repeated were followed up by examination of case-notes or questionnaires to doctors.

Results

Of 111 patients with borderline increased PFM which did not normalize on repeat measurement, 33 were from the hospital and 78 from outside locations. Hospital notes for 27 out of 33 hospital-patients (82%) could be reviewed, and 49 completed questionnaires (63% of 78 sent out) were received from outside locations. Of these 76 patients thus followed up, the test was not repeated in 55 (72%) cases with borderline increased PFM. Of 10 patients with an adrenal mass and borderline PFM, only three had PFM repeated. Of another nine patients with undetermined final diagnosis and borderline PFM, only three had the test repeated.

Conclusion

Seventy-two per cent of borderline increased PFM results were not followed up with appropriate repeat testing, potentially leading to missed detection of phaeochromocytoma. A stronger interpretative comment may encourage appropriate repeat testing in more cases with borderline increased PFM and suspected phaeochromocytoma.

Measurement of urinary metadrenaline and normetadrenaline by liquid chromatography tandem mass spectrometry for the diagnosis of phaeochromocytoma

BACKGROUND

Measurement of metadrenalines has been recommended in the investigation of phaeochromocytoma. Urinary assays remain the most common; however, drug interference is still one of the main challenges for analytical systems. We have developed a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantification of total urinary normetadrenaline and total urinary metadrenaline, which does not require extraction procedures prior to analysis.

METHOD

Total urinary normetadrenaline and total urinary metadrenaline were individually quantified by electrospray ionization in the multiple-reaction monitoring mode. Deuterated internal standards were used and an acid hydrolysis step was used to convert conjugated metabolites into free metadrenalines. Chromatographic separation was achieved using a Phenomenex Luna 3 micro PFP column followed by analysis on an API 3200 LC-MS/MS.

RESULTS

Linearity was exhibited across the calibration range for both normetadrenaline (r = 1, P < 0.0001) and metadrenaline (r = 1, P < 0.0001) with the limit of quantification of 0.05 and 0.02 micromol/L, respectively. Intra-assay imprecision for both normetadrenaline and metadrenaline was less than 5.5% with % coefficient of variations of less than 4%. Inter-assay imprecision was less than 13%. Neither noradrenaline or adrenaline interfere with the assay as determined by the spiking of samples with high concentrations of noradrenaline or adrenaline (P > 0.05). Acceptable analytical performance was seen with comparison to a high-performance liquid chromatography method and on External Quality Assessment returns.

CONCLUSIONS

An analytically simple and sensitive method has been developed and evaluated for the analysis of total urinary normetadrenaline and total urinary metadrenaline which is now in routine use.

Pilot quality assurance programme for plasma metanephrines

Background

Up to 2007 there was no formal external quality assurance programme for plasma free metanephrines. A pilot programme was conceived by the AACB (Australian Association of Clinical Biochemists) Working Party on biogenic amines. With support from the AACB and Royal College of Pathologists of Australasia Quality Assurance programmes, a pilot study was developed. Data from this study are presented for the first time.

Methods

Twelve lyophilized plasma samples were distributed to 15 centres. Samples were spiked with metanephrine (metadrenaline), normetanephrine (normetadrenaline) and 3-methoxytyramine, all derived from human urine. Concentrations were arranged in a linear relationship. The analytes were present at six levels and samples were duplicated.

Results

High-pressure liquid chromatography and tandem mass spectrometry methods showed acceptable precision but in general enzyme immunoassay displayed a higher degree of imprecision as well as a negative bias.

Conclusions

Differences in calibration and matrix effects are likely to have been responsible for the discrepancy between chromatographic and immunoassay methods. These differences need to be further examined although efforts at standardization between different methods have been hampered by the lack of a universal calibrator for plasma metanephrines. Meanwhile, a laboratory's performance characteristics can be monitored and enhanced by participation in suitable external quality assurance programmes.

Simultaneous measurement of urinary metanephrines and catecholamines by liquid chromatography with tandem mass spectrometric detection

BACKGROUND

The measurement of catecholamines and metanephrines in urine is an important diagnostic test in biochemical screening for phaeochromocytoma. Tandem mass spectrometry (MSMS) has the potential to be used in a profiling method for simultaneous assay of these analytes.

METHODS

Optimal conditions were established for the MSMS detection of catecholamines (noradrenalin, adrenalin and dopamine) and metanephrines (normetanephrine and metanephrine), including commercially available isotopically labelled compounds for use as internal standards. Chromatographic separation of all five polar biogenic amines was achieved under solvent conditions that were compatible with MSMS and multiple reaction monitoring. Several types of solid-phase extraction cartridge were used to investigate clean-up conditions for urine, and acid-hydrolysates of urine, prior to LC-MSMS.

RESULTS

Total catecholamines and metanephrines from acid-hydrolysed urines, or free catecholamines and free metanephrines from native urines, were complexed with diphenyl-boronate and recovered in high yield from polymer cartridges after elution with formic acid. Direct injection of eluates into the LC-MSMS system allowed quantitation of catecholamines and metanephrines with a run time of 6 min per sample. Biogenic amine concentrations for patient urines and quality assurance programme samples, and assay imprecision, were similar to values obtained with high-performance liquid chromatography methods, which used electrochemical detection. In normal urines, the ratio of free to total catecholamines was around three-fold higher than the ratio of free to total metanephrines.

CONCLUSION

The assay of urinary catecholamines and metanephrines can be achieved simultaneously using one LC-MSMS method, which is rapid and reduces labour and consumable costs for routine application.