Seasonal variations in vanillylmandelic acid and homovanillic acid in infants' urine.

Seasonal variations in urinary levels of vanillylmandelic acid (VMA) and homovanillic acid (HVA) have been investigated over a two-year period, using 31,466 filter-paper specimens of urine from infants of 6 months of age who underwent Sapporo City's screening for neuroblastoma. Levels of both VMA and HVA (micrograms/mg creatinine) were significantly higher in summer (11.48 +/- 7.40, n = 7,569, and 18.70 +/- 8.18, n = 7,582, respectively) than in winter (10.72 +/- 5.76, n = 8,143, and 16.46 +/- 7.17, n = 8,148, respectively) throughout the two years (P less than 0.01, t-test). Although the cause of this difference could not be found, its actual clinical relevance was thought to be small since there was no significant relation between monthly rate of re-screened infants and monthly mean levels of VMA or HVA (P greater than 0.05, Spearman-Rank correlation).