Objective: To investigate the positive predictive value (PPV) of urinary vanillylmandelic acid (VMA) testing in the diagnosis of phaeochromocytoma and to describe the features associated with phaeochromocytoma at the University Hospital of the West Indies (UHWI).
Subjects and Methods: There were 551 VMA tests performed from January 2003 to June 2009 and 122 tests in 85 patients were elevated (ie ≥ 35 μmol/24 hr). The study patients were categorized as: (i) ‘surgical’ (5 patients who underwent surgery) or (ii) ‘non-surgical’ (remaining 80 patients). Forty medical charts (out of 85) were reviewed using a standardized data extraction form.
Results: The median age for patients in the non-surgical group (with charts reviewed, n = 35) was 36 years (range 9–70) and the median VMA was 43 μmol/24 hr (IQR 38–51). Of these patients, 83% had one or no symptom typical of phaeochromocytoma. In the surgical group the median VMA was 58 μmol/24 hr (IQR 44-101); phaeochromocytoma was confirmed histologically in 3 patients, all of whom had several symptoms typical of catecholamine excess. VMA testing had a PPV of 8%, specificity of 79% and sensitivity of 100%.
Conclusions: VMA testing at UHWI has poor specificity and high sensitivity. These results contrast with international data showing that VMA testing is poorly sensitive but highly specific. The use of assays with higher specificity (eg plasma or urinary metanephrines) may represent a more cost-effective approach to biochemical screening at UHWI.