Background: The accuracy of homocysteine (Hcy) results is currently compromised by the requirement to separate the plasma within 1 h of sample collection. We studied the effect of temperature on the stability of plasma Hcy over a 72-h time course in blood collected into evacuated tubes containing either EDTA alone or both EDTA and 3-deazaadenosine (3DA). Methods: We recruited 100 volunteers, including both diseased and healthy individuals with a range of baseline plasma Hcy values, from two

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... ers. Blood samples were collected into tubes containing EDTA, and EDTA plus 3DA and stored at ambient temperature (20–25 °C) or refrigerated (2–8 °C). Aliquots of blood were centrifuged at various times up to 72 h, the plasma was removed, and Hcy was measured by HPLC. Results: Plasma Hcy measurement covering the sample collection and storage conditions during the whole time course was possible on samples from 59 of those recruited. One-way ANOVA for repeated measures within subjects revealed that only samples that were collected into tubes containing EDTA plus 3DA and stored refrigerated were stable over 72 h (P = 0.2761). Conclusions: A combination of 3DA and storage at 2–8 °C will allow collection of samples for plasma Hcy measurement outside of the hospital setting and wider population screening.