A modified procedure for determining metanephrines in urine

We have modified the procedure for determining total metanephrines in urine described by Gupta, Price and Keane(1) to shorten the time necessary for completion while allowing the technician time to perform other tests. The modification involves the extraction of interfering substances from urine. Instead of having to extract 3 individual tubes for each patient, we have developed an extraction that can be performed in a single tube per sample. This allows the number of tubes handled in the first portion of the procedure to be reduced by 66% and a reduction in analysis time of 25%. Day-to-day precision of the method is 8.7%. The modified procedure was compared to the original procedure by running 38 different patients by each method. The mean for the original and modified method were 1.1 mg/24h and 1.1 mg/24h respectively. The correlation coefficient was 0.9051. The t-test (p = 0.05) indicated that there was no significant difference in the means of the methods and the F-test (p = 0.05) indicated that there was no significant difference in the precision of the methods.