BSAVA Petsavers Article: Validation of an ELISA assay for measurement of the metabolite of serotonin, 5-hydroxyindole acetic acid (5-HIAA), in canine urine.

ELISA validates as reliable non-invasive alternative for measuring canine urinary 5-HIAA.

This study validates a commercially available ELISA assay for measuring 5-hydroxyindole acetic acid (5-HIAA), a urinary metabolite of serotonin, in dogs. Serotonin's short serum half-life makes direct measurement unreliable; therefore, measuring urinary 5-HIAA after an 8-hour fast provides a more stable indicator of circulating serotonin levels, similar to established protocols in human medicine. Urine samples from 26 dogs were analyzed using both ELISA and liquid chromatography-tandem mass spectrometry (the gold standard). The ELISA demonstrated acceptable precision and repeatability with a coefficient of variation below 20%. Bland-Altman and Deming regression analyses showed good agreement between methods, with minimal bias (0.92 μmol/L) and acceptable limits of agreement. However, the assay's reliability at upper analytical measurement range limits was not adequately tested. The authors conclude that ELISA is a reliable, non-invasive alternative to blood sampling, particularly at low concentrations, though high concentrations may exceed acceptable error margins. Further validation in normal and diseased dogs is necessary before clinical implementation.

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