Dietary flavonols contribute to false-positive elevation of homovanillic acid, a marker of catecholamine-secreting tumors

BackgroundUrinary homovanillic acid (HVA) measurement is used routinely as a marker of the first test for the screening of catecholamine-secreting tumors and dopamine metabolism, but generates a large number of false-positive results. With no guidelines for dietary restrictions prior to the test, we hypothesize that consumption of flavonol-rich foods (such as onions, tomatoes, tea) prior to urinary catecholamine screening could be responsible for false-positive urinary HVA in healthy subjects.MethodsA randomized, crossover dietary intervention was carried out in healthy subjects (n = 17). Volunteers followed either a low or high-flavonol diet, for a duration of 3 days, prior to providing a 24-h urine sample for HVA measurement using a routine, validated liquid chromatography method as well as a gas chromatography-mass spectrometry method.ResultsDietary flavonol intake significantly increased urinary HVA excretion (p < 0.001), with 3 out of 17 volunteers (20%) exceeding the 40 μmol/24 h upper limit of normal for HVA excretion (false-positive result).ConclusionDietary flavonols commonly found in foodstuff such as tomatoes, onions, and tea, interfered with the routine urinary HVA screening test and should be avoided in the three-day run-up to the test.