L-DOPA therapy interferes with urine catecholamine analysis in children with suspected neuroblastoma: a case series.

Neuroblastoma is the most common solid extracranial malignancy diagnosed in childhood. Clinical presentation is variable, and metastatic disease is common at diagnosis. Analyses of urinary catecholamines and their metabolites are commonly requested as a first-line investigation when clinical suspicion exists. Levodopa (L-Dopa) therapy is utilized as a treatment for a number of disorders in childhood, including Dopa-responsive dystonia. Neuroblastoma may mimic some of the clinical features of this disorder. L-Dopa can interfere with analysis of urinary catecholamines and their metabolites and complicate the interpretation of results. We present the cases of three children who were prescribed L-dopa at the time of analysis of urinary catecholamines and metabolites as a screen for neuroblastoma, but who did not have the disease. Comparison of their results with those from cases with true neuroblastoma reveal that it is impossible to reliably distinguish true neuroblastoma from L-Dopa therapy using these tests. We recommend that patients should be off L-dopa therapy, if possible when these tests are performed. These cases illustrate the importance of providing clinical details and drug history to the laboratory in order to avoid diagnostic confusion.

A survey of some pre-analytical errors identified from the Biochemistry Department of a Scottish hospital.

BACKGROUND: It is estimated that 70% of all health care decisions affecting diagnosis or treatment involve laboratory testing. The pre-analytical phase of the testing process shows the highest prevalence of errors accounting for 70% of all mistakes in laboratory diagnostics. It is recommended that laboratories collect statistics on pre-analytical error rates. This survey examined some mistakes in blood collection, i.e. specimen haemolysis, and EDTA contamination. METHODS: Survey was from June 2011 to May 2012. Haemolysis was detected by analysers' automated haemolysis index function. Plasma EDTA was measured by an automated system. Data were captured from our laboratory information management system. RESULTS: For a total workload of 763,577 blood specimens, the overall haemolysis rate was 3.2%. Much higher rates of both specimen haemolysis and EDTA contamination were observed when blood was not collected by trained phlebotomists. CONCLUSIONS: Better training in blood collection, achieving the standard of professional phlebotomists, will improve validity of diagnostic information; reduce risks of dangerous misinterpretation of results, unwanted anaemia and needlestick injury and decrease laboratory supplies costs. This type of audit could be replicated in other Scottish Health Boards with some benefit and thereby better target future training needs.

Detection of creatine kinase macroenzymes.

BACKGROUND: It is vital to detect macroenzymes in patients' plasma or serum since their presence may lead to spurious elevation of enzyme activity, thereby causing diagnostic confusion. Our service for macroenzyme detection has been made available to laboratories throughout the UK. This report describes our laboratory's experience with macro-creatine kinase (CK) detection over a 10-year period. METHODS: In each sample received, the presence of macro-CK was looked for by both polyethylene glycol percent precipitable activity (%PPA) and isoenzyme electrophoresis (IsoEP). The accumulated findings over 10 years were reviewed. RESULTS: Out of a total number of 255 requests received from throughout the UK, 30 patients (11.8%) were found to be positive for macro-CK (28 type 1 and 2 type 2). Among those found to be positive, the total CK elevation was relatively modest and the %PPA positively correlated with macro-CK by IsoEP and densitometry (Spearman r(s) = 0.631). The upper reference limit for %PPA of CK could be increased from 37% to 45% after assessment by both an International Federation of Clinical Chemistry-approved calculation and by receiver operating characteristic curve analysis. CONCLUSIONS: Adoption of this change would allow for a more cost-effective investigation protocol. More than 80% of those positive for macro-CK type 1 (immunoglobulin bound) were female, which conforms to findings in many autoimmune processes.

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.

Age-related medical decision limits for urinary free (unconjugated) metadrenalines, catecholamines and metabolites in random urine specimens from children.

BACKGROUND: Neuroblastoma is the most common extracranial solid tumour in childhood (8% of all childhood cancers), the most frequently diagnosed in infancy, and has one of the highest death rates, while chromaffin tumours rarely present in childhood. Both tumour types produce catecholamines and their metabolites. It is difficult to produce reference ranges for tests in children, and currently, no age-related medical decision limits for free metadrenalines (free metanephrines) in random urine specimens exist in the paediatric literature. METHODS: Results of vanillylmandelic acid (VMA), 5-hydroxyindoleacetic acid, homovanillic acid (HVA), noradrenaline (NA), adrenaline, dopamine (DA), free normetadrenaline (fNMA), free metadrenaline and free 3-methoxytyramine (f3MT) in 1658 random urines obtained from infants, children and young adults were measured by high performance liquid chromatography with electrochemical detection. Specimens were excluded from consideration if obtained from the following categories, i.e. (a) harbouring neuroblastic, chromaffin, carcinoid or other tumours or malignancies; (b) medical conditions having known association with excess catecholamine excretion; (c) patients administered catecholamine or paracetamol; (d) overly dilute urine; and (e) manifesting outlying values following visual inspection. RESULTS: There remained 872 specimens that were grouped into seven age ranges (<1; 1 or 2; 3 or 4; 5-7; 8-10; 11-13; 14-19 y) for which medical decision limits were determined for each analyte. There was no significant difference between the results for boys or girls. In 55 patients harbouring neuroblastic tumours, HVA (54/55), f3MT (14/16), VMA (45/53) and DA (43/53) were the most frequently elevated analytes at time of diagnosis. In 11 patients presenting in childhood with chromaffin tumours, fNMA (11/11) followed by NA (10/11) were the most frequently elevated. Discussion The likely reasons for outlying or missing values, together with the reasons for variation in the distinctive biochemical patterns of analytes exhibited in individuals harbouring either neuroblastic or chromaffin tumours are discussed.

Dietary flavonols contribute to false-positive elevation of homovanillic acid, a marker of catecholamine-secreting tumors.

BACKGROUND: Urinary homovanillic acid (HVA) measurement is used routinely as a marker of the first test for the screening of catecholamine-secreting tumors and dopamine metabolism, but generates a large number of false-positive results. With no guidelines for dietary restrictions prior to the test, we hypothesize that consumption of flavonol-rich foods (such as onions, tomatoes, tea) prior to urinary catecholamine screening could be responsible for false-positive urinary HVA in healthy subjects. METHODS: A randomized, crossover dietary intervention was carried out in healthy subjects (n=17). Volunteers followed either a low or high-flavonol diet, for a duration of 3 days, prior to providing a 24-h urine sample for HVA measurement using a routine, validated liquid chromatography method as well as a gas chromatography-mass spectrometry method. RESULTS: Dietary flavonol intake significantly increased urinary HVA excretion (p < 0.001), with 3 out of 17 volunteers (20%) exceeding the 40 µmol/24 h upper limit of normal for HVA excretion (false-positive result). CONCLUSION: Dietary flavonols commonly found in foodstuff such as tomatoes, onions, and tea, interfered with the routine urinary HVA screening test and should be avoided in the three-day run-up to the test.

Childhood phaeochromocytoma and paraganglioma: 100% incidence of genetic mutations and 100% survival.

INTRODUCTION: The aim is to identify the incidence of genetic mutations and outcome of children presenting with phaeochromocytoma/paraganglioma (PGL) to a single paediatric surgical service to determine the need for genetic counselling in associated kindreds. METHODS: A retrospective case note review was undertaken of all cases treated between 1998 and 2008 with particular reference to presentation, management, and predisposing genetic conditions. RESULTS: Seven cases (4 male, 3 female) were identified (median age, 13 years; interquartile range, 9-16). Three cases had a family history of phaeochromocytoma/PGL. All presented with neurologic symptoms related to hypertension, including headaches (n = 5), hemiparesis (n = 2), facial palsy, and hemianopia. All underwent surgical resection. Five patients had meta-iodobenzylguanidine (MIBG) therapy for apparently malignant features. All cases were found to have a predisposing genetic mutation: von Hippel-Lindau (n = 3), succinate dehydrogenase mutations (n = 3), and multiple endocrine neoplasia (n = 1). All patients are alive after a median follow-up of 5 (interquartile range, 2-7) years. CONCLUSIONS: All 7 cases had a familial genetic mutation identified, and none arose de novo. We advocate genetic counselling for all families of children diagnosed with phaeochromocytoma/PGL with lifelong surveillance tailored to the underlying syndrome because of the increased risk of synchronous and metachronous tumours associated with these genetic syndromes.

Reliability of urine collection pads for routine and metabolic biochemistry in infants and young children.

The aim of our study was to evaluate whether specifically designed urine collection pads give reliable results for routine and metabolic biochemistry tests in paediatric urine. Urine collected by bag or clean-catch from infants and children <2 yrs without metabolic disorders was divided into two aliquots, one of which was added to a collection pad, incubated for 15 min at 37 degrees C (simulating in vivo collection conditions), then recovered by aspiration. Urine from adults with phaeochromocytoma and aqueous solutions of catecholamines were similarly treated. Routine, catecholamine, and metabolic analyses were performed on pad/non-pad aliquots. Selected metabolic analyses were also performed on pad/non-pad urine from patients with diagnosed inborn errors and urine containing added metabolites to simulate metabolic disorders. Routine tests (urea, electrolytes, creatinine, osmolality, calcium:creatinine, phosphate:creatinine, magnesium:creatinine, urate:creatinine [n = 32], oxalate:creatinine [n = 10]), and catecholamines (n = 12) showed good or acceptable concordance with no clinically significant pad/non-pad differences. Metabolic tests in infants and children without metabolic disorders all showed good pad/non-pad concordance for amino acids (n = 10), organic acids (n = 12), and glycosaminoglycans (n = 8). In patients with metabolic disorders (phenylketonuria [n = 1], homozygous/heterozygous cystinuria [n = 3], mucopolysaccharidoses II [n = 2] and III [n = 1], organic acid disorders [n = 6]) and urine containing added orotic acid to simulate urea cycle disorders, there was also good pad/non-pad concordance for diagnostic urinary metabolites. No extraneous organic acids were eluted from the pads. Sugar chromatography showed identical staining intensity in pad/non-pad samples. In conclusion, urine collection pads give reliable results for a wide range of routine and metabolic biochemistry tests in urine from paediatric patients.

Comparison of diagnostic accuracy of urinary free metanephrines, vanillyl mandelic Acid, and catecholamines and plasma catecholamines for diagnosis of pheochromocytoma.

CONTEXT: Recent evidence suggests that plasma-free metanephrines provide a highly sensitive test in patients requiring exclusion of pheochromocytoma. The diagnostic efficacy of urinary free metanephrines, however, has not been evaluated. OBJECTIVE, DESIGN, SETTING, PATIENTS, AND OUTCOME MEASURES: We compared retrospectively the diagnostic efficacy of 24-h urinary free metanephrines with our currently available measurements of 24-h urinary vanillyl mandelic acid (VMA), urinary catecholamines, and plasma catecholamines in 159 outpatients tested in a tertiary referral center for pheochromocytoma over a 4-yr period. RESULTS: The sensitivity of urinary free metanephrines was 100% [25 of 25 patients; 95% confidence interval (CI) 86-100%)] compared with the sensitivity of 84% (21 of 25; 95% CI 64-95%) for urinary catecholamines; 72% (18 of 25; 95% CI 51-88%) for urinary VMA; and 76% (16 of 21; 95% CI 53-92%) for plasma catecholamines. The specificity of urinary free metanephrines was 94% (116 of 123; 95% CI 89-98%), compared with the specificity of 99% (127 of 129; 95% CI 96-100%) for urinary catecholamines; 96% (130 of 134; 95% CI 91-98%) for urinary VMA; and 88% (66 of 75; 95% CI 78-94%) for plasma catecholamines. Receiver operating characteristic curves for all test groups were generated. Pairwise comparisons of the area under the receiver operating characteristic curve for urinary free metanephrines with that of each of the other three test groups individually were: 0.993 (95% CI 0.962-0.999) vs. 0.919 (95% CI 0.862-0.957, P = 0.032) for urine catecholamines; 0.993 (95% CI 0.962-0.999) vs. 0.846 (95% CI 0.778-0.900, P = 0.002) for urine VMA; and 0.992 (95% CI 0.945-0.998) vs. 0.852 (95% CI 0.762-0.918, P = 0.009) for plasma catecholamines. Testing with urinary free metanephrines failed to misidentify a single case of pheochromocytoma, compared with four missed cases for urinary catecholamines, seven missed cases for urinary VMA, and five missed cases for plasma catecholamines. CONCLUSION: Urinary free metanephrines were superior to urinary VMA, urinary catecholamines, and plasma catecholamines and can provide a valuable test for diagnosis of pheochromocytoma in adults.

Outcomes of discretionary laboratory requesting of serum protein electrophoresis.

BACKGROUND: Discretionary laboratory requesting of serum protein electrophoresis (SPE) is widespread throughout the UK despite limited evidence to support clinical usefulness. We aimed to examine the clinical usefulness of discretionary SPE requesting on serum samples with globulins>45 g/L by documenting the number of discretionary tests performed and the number of paraproteins identified in an audit period, by determining if such findings led to further investigation/specialty referral, and by identifying the final diagnosis and subsequent management of these patients. METHODS: A retrospective one-year audit from July 2002 to June 2003 was carried out using information from biochemistry databases and review of medical records. RESULTS: Of 1332 discretionary SPEs performed in one year, 72 paraproteins were identified (5.4%). Further clinical information could be obtained in 66 cases. Appropriate follow-up occurred in 84% of cases. The most common diagnosis was monoclonal gammopathy of undetermined significance (56%). Eighteen percent of patients with an identified paraprotein were diagnosed with B-cell malignancies that warranted treatment. A further 6% progressed to requiring treatment during follow-up. CONCLUSION: Using screening criteria of serum globulins>45 g/L, one in 20 discretionary laboratory requests resulted in a clinically relevant finding. These results suggest such requesting is worthwhile and should aid future debate on the appropriateness of this practice.

Elevated urinary dopamine in adults and children.

BACKGROUND: Information on the significance of an elevated urinary dopamine is limited and can lead to misinterpretation of the cause of such a finding. This laboratory-based study examines the associations with elevated dopamine gathered from a significant number of patients. METHODS: The urine catecholamine and metabolite results of specimens (analysed by HPLC-ECD) from 5933 adults and 467 children were examined retrospectively over a 57-month period. Those with elevated dopamine were identified and the explanation for this finding was sought. RESULTS: In adults, the conditions associated with an elevated dopamine were: urine over-collection; drug effects (including those due to intravenous dopamine, L-dopa, methyldopa, clozapine, antidepressants and metoclopramide); clinical effects (including those due to phaeochromocytoma, carcinoid tumour and pregnancy). In children, high urine dopamine was found in cases of neuroblastoma, Costello syndrome, leukaemia, phaeochromocytoma, Menkes disease and rhabdomyosarcoma of the bladder. CONCLUSIONS: A high urine dopamine was found in <3% of adult urine specimens. It was most commonly associated with: over-collection, probable drug effects and neural crest tumours. Neuroblastoma was the most common cause of elevated dopamine in children's specimens, although other associations are described. Some await explanation.

Macroenzyme detection by polyethylene glycol precipitation.

BACKGROUND: The presence of macroenzymes can cause significant diagnostic confusion and their detection can involve relatively cumbersome analytical procedures. METHODS: Using a simplified polyethylene glycol precipitation technique and isoenzyme electrophoresis, this report describes the construction of reference ranges of precipitable activity for each of seven commonly measured enzymes in plasma. RESULTS: The proposed reference ranges are reported. Since introducing the protocol, 12 cases of macroenzymaemia have been encountered. Three typical case histories are described in some detail. CONCLUSIONS: The polyethylene glycol precipitation method has thus far proved to be a simple and effective additional test for the detection of macroenzymes when the plasma enzyme activity is elevated.

Effects of contamination of blood specimens with liquid potassium-EDTA anticoagulant.

BACKGROUND: Use of the anticoagulant EDTA, in high-concentration liquid form, in blood collection tubes can lead to cross-contamination of routine biochemistry specimens. METHODS: In the present study, tests affected by EDTA in the sample were potassium, calcium, magnesium, unsaturated iron-binding capacity, bicarbonate, aspartate transaminase, alanine transaminase, lactate dehydrogenase, creatine kinase, alkaline phosphatase and amylase. The likely mechanisms are discussed. CONCLUSIONS: In the interests of best practice, the identification of subtle contamination of blood specimens for biochemical analysis requires a sensitive method for measurement of EDTA itself.

Phaeochromocytoma with normal urinary catecholamines: the potential value of urinary free metadrenalines.

BACKGROUND: Normal urine catecholamine values in patients with phaeochromocytoma is an occasional finding and may lead to a missed diagnosis. Additional urinary free metadrenaline analysis may be of value in this situation. METHODS: In addition to vanillylmandelic acid, homovanillic acid and the catecholamines, urinary free normetadrenaline (fNMA) and free metadrenaline (fMA) were measured. This report describes six confirmed cases of phaeochromocytoma showing normal urinary catecholamine output and compares fMA results and tumour size with other confirmed cases where the urine catecholamines were increased. RESULTS: Urine catecholamines in these patients with, on average, smaller tumours, were all normal. Urinary fNMA and fMA were available on five patients, and were increased in three. The data suggest that, unlike the catecholamines, urinary fNMA and fMA could be a useful predictor of tumour size. CONCLUSION: The inclusion of fNMA and fMA in the test profile is likely to be of additional benefit in tumour detection, particularly when catecholamines or other metabolites are normal.