Lack of uniformity in the clinical approach to the interpretation of urinary catecholamines and their metabolites

A study of the case notes from 101 of the 113 instances where at least one of the results was abnormal from the analysis of 24 hr urinary collections for noradrenaline, adrenaline, and dopamine and their metabolites 4-hydroxy-3-methoxy-mandelic acid (HMMA) and homovanillic acid (HVA) in screening for phaeochromocytomas in hospitals affiliated to the Royal College of Surgeons in Ireland Medical School from a total of 199 false positives from all sources shows that 51% had a second sample, 33% had ultra sound, 12% had a CT scan, 6% had an¹³¹I metaiodobenzylguanadine (MIBG) scan, 40% had no imaging performed and in 5% the reports were not received by the referring medical team. The 12 sets of data where case notes could not be retrieved were disregarded. Of the 22 patients with one or more biochemical value greater than twice the upper reference range, 8 had not, by our criteria had a phaeochromocytoma positively excluded. The sensitivity and specificity for phaeochromocytoma diagnosis for the free catecholamines together was 82% and 88.4%; for HMMA 60% and 95.8%; and for catecholamines and HMMA together 82% and 93.2% respectively. A protocol which includes repeat samples where results are abnormal and the appropriate use of diagnostic imaging should be systematically pursued to minimise false negative diagnoses.