When evaluating a specimen for DAT testing, our practise has been to accept a specimen up to 24 hours old, refrigerated if not tested within a couple of hours of collection is preferred. Some of us have been taught that older specs may yield a false positive or a false negative; others just a false positive. We would like to clarify our procedure. I would appreciate any guidance on specimen age and impact on DAT results. What is your practise? Can you point me to any references? Thanks!