Urinary VMA, dopamine and the likelihood of neuroblastoma: a preferred way of reporting laboratory results?
BACKGROUND
Neuroblastoma patients may be classified as normal or abnormal depending on reference interval and decision points for urine catecholamine metabolites. We therefore evaluated the utility of positive likelihood ratios (LR+) based on data from patients in whom the diagnosis was suspected.


METHODS
Urine samples from 249 patients (122 male, 127 female) suspected of neuroblastoma were assayed for VMA by spectrophotometry and dopamine by HPLC. Ratios of VMA to creatinine (VMA/Cr) and dopamine to creatinine (DA/Cr) were calculated and age-related median scores derived relative to patients without neuroblastoma. Receiver operator characteristic (ROC) curve analysis was undertaken for the ability of median scores to identify neuroblastoma.


RESULTS
Of the 249 patients, there were 20 confirmed cases of neuroblastoma, with ages ranging from 0 (congenital tumour) to 8.4 years. From ROC curves, VMA/Cr was found to have an area under the curve 0.96 (95% confidence interval [CI] 0.92-0.98) compared with 0.72 (95% CI 0.66-0.77) for DA/Cr, P=0.001. At the optimal decision point for VMA/Cr, LR+ was 7.2, identifying cases with a sensitivity of 95% and a specificity of 86%, and comparing favourably with published intervals.


CONCLUSIONS
VMA/Cr is more accurate than DA/Cr for the diagnosis of neuroblastoma. Reporting LR+ may also be more informative than using reference intervals and decision points.
Sies
C W
CW
Clinical Biochemistry Unit, Canterbury Health Laboratories, PO Box 151, Christchurch, New Zealand. Chris.sies@cdhb.govt.nz
Florkowski
C M
CM
Sullivan
M
M
Mackay
R
R
George
P M
PM
D002395:Catecholamines / Q000652:urine; D002624:Chemistry, Clinical / Q000379:methods*; D002648:Child; D002675:Child, Preschool; D004298:Dopamine / Q000652:urine*; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007773:Lactates / Q000652:urine; D008297:Male; D009447:Neuroblastoma / Q000175:diagnosis* / Q000652:urine*; D012372:ROC Curve; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014642:Vanilmandelic Acid / Q000652:urine*
D002395:Catecholamines; D007773:Lactates; C005434:atrolactic acid; D014642:Vanilmandelic Acid; D004298:Dopamine