Study of the La Brosse Spot Test for 3-Methoxy-4-hydroxymandelic Acid (VMA)

The object of this paper is to compare the La Brosse test with the quantitative urinary VMA measurement (Pisano's technique). Substances whose breakdown products appear in the urine and give false positive results were eliminated from the diet. Seven hundred 24-hr urine samples belonging to 580 patients were studied. Fifty-six patients had sympathoblastomas, 15 pheochromocytomas; the remaining several pathologies were not related to a catecholamine increase. Four hundred twelve negative, 132 intermediate, and 156 positive reactions were obtained. The negative tests had normal VMA in all cases except in five urine samples (false negative) belonging to three patients with pheochromocytoma who had increased VMA (between 15.4 and 38.6 mg/24 hr). The intermediate results had normal VMA in all cases except one patient with pheochromocytoma (VMA 18.4 mg/24 hr). Among the positive tests, 70 showed increased VMA and 86 normal VMA (false positive FP). The former results belonged to 55 samples from sympathoblastoma patients and to 15 from pheochromocytoma patients. The FP occurred in 15 patients treated for sympathoblastoma and in 71 patients without any pathology associated with a catecholamine increase. Of the sympathoblastoma patients, 30 were studied before any treatment (group I) and 26 after treatment (group II). In group I, all but 1 yielded positive tests: 28 had increased VMA and 2 had normal VMA. From this group, 16 patients were followed during treatment: 11 continued with positive tests and increased VMA excretions and 5 converted to negative tests and normal VMA. In group II, 19 were negative, 4 were intermediate, and 3, all with normal VMA, were positive. Only one patient persisted with positive tests in the subsequent evaluations. In conclusion, the La Brosse test is a practical screening test to detect and follow the course of treatment in patients with sympathoblastoma who initially had positive tests and increased VMA. All these results must be interpreted with caution because there are false positive results and a 15% of sympathoblastoma patients have normal VMA. The false negative results (1.2%) were observed in 17% of pheochromocytoma patients. The intermediate reactions were associated with normal VMA excretions except in one pheochromocytoma patient.