Background: 5-Hydroxyindoleacetic acid (5-HIAA) is the main metabolite of serotonin and is measured in all patients newly diagnosed with neuroendocrine tumours both to diagnose carcinoid syndrome and to monitor treatment response for those with an elevated baseline level. Each test requires patients to avoid certain foods and collect urine over a 24 hour period. It is not known to what extent patients adhere to these requirements or find them burdensome. There is now a validated serum 5-HIAA assay available and patients at the Royal Marsden Hospital will be switched to this test which allows an opportunity to assess patient experience of the two methods.
Aim: To determine adherence to dietary restriction prior to 5-HIAA testing, challenges with 24 hour urine testing and patient preference for method of testing.
Methods: A prospective questionnaire was administered to patients after they completed paired tests for urine and plasma 5-HIAA. Responses were entered into an Excel spreadsheet along with data for a cohort of patients who undertook paired samples, and descriptive analysis was performed.
Results: 20 patients completed the questionnaire. 75% of patients were required to test every 3-10 months as part of their monitoring. Two patients (10%) reported incomplete urine collections, but this was less than half of the time. Three patients (15%) reported difficulties in returning the urine bottle to the laboratory. 75% of patients were aware of the dietary requirements associated with 5-HIAA assessment and all followed these requirements. One patient (5%) preferred urine testing, 16 (80%) preferred plasma, and 3 (15%) had no preference. From a cohort of 31 paired samples, there was an 81% concordance rate between urine and plasma 5-HIAA.
Discussion: Our questionnaire results demonstrate that compliance with urinary testing for 5-HIAA was very good in our cohort with infrequent incomplete collections, although many patients did find the requirements impractical and inconvenient. For patients who were aware of the dietary requirements, compliance was 100%. There was a significant positive preference of patients towards plasma testing. Laboratory concordance was very high with increased sensitivity of plasma testing likely to explain most of the discordant results.