New study validates simple urine test to measure serotonin metabolite in dogs
9 April 2026
A new study, funded by BSAVA PetSavers and published in the Journal of Small Animal Practice, has successfully validated a commercially available ELISA test for measuring 5‑hydroxyindoleacetic acid (5‑HIAA) – the metabolite of serotonin – in the urine of dogs.
Serotonin has been implicated in several canine diseases, including myxomatous mitral valve disease, pulmonary hypertension and dilated cardiomyopathy. Due to the short half-life in the serum, direct measurement of serotonin in blood is challenging, and urinary 5‑HIAA is considered a more accurate marker of serum serotonin concentration in humans. While urine 5-HIAA has previously been measured in dogs using gas chromatography mass spectrometry and high-performance liquid chromatography with electrochemical detection, these techniques are expensive and not widely available.
Researchers from the Queen’s Veterinary School Hospital, University of Cambridge, collected urine samples from 26 dogs undergoing routine diagnostic evaluation at a referral hospital. Each sample was analysed and compared using both a commercially available ELISA testing kit (Ref: BA-E-1900, Immusmol) and the current gold standard method – liquid chromatography-tandem mass spectrometry (LC‑MS).
The ELISA was found to be reliable with acceptable precision and repeatability, particularly at low concentrations, but had a slightly higher observed error at higher concentrations. As it provides a more accessible, less invasive, and relatively low-cost method to assess 5‑HIAA in dogs, this would make the ELISA more widely available for veterinary clinicians than LC-MS, and may be helpful in investigating the role of serotonin in various canine diseases.
The researchers recommend that further validation work be carried out to improve understanding of the various preanalytical factors that may influence the measurement of 5-HIAA concentrations. Further work should also investigate whether measuring urinary 5-HIAA will be a good surrogate marker for physiologically active circulating serotonin in dogs, and whether it will be useful in studying disease pathogenesis.
Dr Penny Watson, senior author of the study, said: “I am very hopeful that, after further validation, this ELISA will prove to be a reliable, simple and cheap test for 5-HIAA in the urine, facilitating further research into the role of serotonin in the pathogenesis of canine diseases.
“We have long suspected that some individual dogs and breeds may have higher circulating serotonin than others and that this might predispose them not only to heart disease but also some common diseases such as chronic pancreatitis and kidney disease. They would also be more susceptible to serotinergic syndrome when medicated with drugs such as tramadol or trazadone. Further research in this area would thus be directly relevant to small animal practitioners.”