Screening procedures for neuroblastoma: false-negative results.

Since elevation of 3-methoxy-4-hydroxymandelic acid (VMA) excretion frequently occurs in patients with neuroblastoma, simpler methods have been developed to differentiate between high and low levels of VMA in the urine, namely the LaBrosse spot test and VMA test strips. Sensitivity of these two procedures depends upon the concentration of VMA in the urine rather than total amount of VMA excreted. VMA excretion data from patients with neuroblastoma show that even though the total amount of VMA excreted in a 24-hour period may definitely be elevated, the concentration of VMA in the 24-hour urine samples may vary greatly from one day to the next and from one patient to another. Therefore, these rapid screening methods for urinary VMA would appear to be too insensitive to use as the sole means of detection or follow-up of patients with neuroblastoma since these techniques require a high concentration of VMA.