Simultaneous measurement of VMA and HVA in 24-hour urine samples

A simple method is described for the simultaneous measurement of vanillylmandelic acid (VMA) and homovanillic acid (HVA) in 24-hour urine samples based upon isocratic high-performance liquid chromatography with electrochemical detection (HPLC-ECD). VMA was measured using VMA-SKREEN kits (Biochemical Diagnostics), a microcolumn diazo method and HPLC-ECD test method. HVA was measured using Bio-Rad HVA HPLC reagent kits (Bio-Rad Laboratories) and the test method. No significant statistical difference was found in mean or variance when this method was compared with the micro-column diazo method for VMA and HPLC-ECD for HVA using the commercial anion-exchange kit. The linear regression equation for VMA was ŷ = 0.92 x + 0.21, and for HVA was ŷ = 1.10 x + 0.06. The Pearson correlation coefficient for VMA was r = 0.896 and for HVA was r = 0.996. This method yields results for 24-hour urinary VMA and HVA that compare well with established commercial methods.