ABP Operating Guidelines  – Version 9.0 – July 2023  Page 42/91 4.0 Assay Pre -analytical Procedure  − The Laboratory  should (usually) receive refrigerated (not frozeni) “A” and “B” blood Samples , which have been collected in blood tubes containing an inert polymeric serum separator  gel and a clotting activation factor (for example: BD Vacutainer® SSTTM-II Plus  tubes, EU ref 367955; BD Vacutainer® SSTTM-II Plus Advance tubes, EU ref 367954; BD Vacutainer® SSTTM tubes, US ref 367986 ) in accordance with the International Standard  for Testing and Investigation (ISTI) 7;  − Alternatively, if the clotting and centrifugation of the Sample  is performed prior to reception at the Laboratory  (for example, at the site of Sample  collection),  Samples may be received at the Laboratory  as frozen/refrigerated blood Samples  either in the same Sample collection tubes  or as separated serum in new tubes;  − The Laboratory  shall c heck  the status of the Sample(s)  (e.g., evidence of hemolysis) and the integrity of the collection tubes ( e.g., evidence of breakage of the separating gel).