in our lab we collect serum, but I don't know why. Is there any difference to be found while doing ELISA with Serum and Plasma?plasma was collected via EDTA vacutainer tubes or heparin tubes?.
As a general point, the more pure test medium, the more accurate and reliable measurement. Plasma have coagulation proteins plus anticoagulant. These may interfere with assay, especially in competitive elisa and HPLC. Thus serum is more pure than plasma. I faced some problem in enzyme assay and protein quantification when used plasma, but not serum.