Serum gel tubes

Blood samples were obtained while patients were being evaluated in the Diagnostic Outpatient Clinic at Herlev and Gentofte Hospital and before a diagnosis was finally made. Peripheral blood was collected in one K3EDTA tube (1 × 9 ml), two serum gel tubes (2 × 8 ml) and two PAXgene blood RNA tubes (2 × 2.5 ml) (Becton & Dickinson). Samples were processed according to the nationally approved standard operating procedure for blood collection and handling. Whole blood (1 × 1.5 ml) was aliquoted and stored at −80°C. Within 2 h, tubes were centrifuged at 2000g at 4°C for 10 min. After centrifugation, EDTA plasma, buffy coat and serum were aliquoted into two tubes with 2 ml plasma EDTA, one tube with 1.5 ml buffy coat (from the EDTA tubes) and 4 tubes with 2 ml serum. Buffy coat, EDTA plasma and serum were stored at −80°C. The 2.5 ml whole blood in two PAXgene blood RNA tubes was collected and handled according to the manufacturer's instructions. PAXgene blood RNA tubes were kept at room temperature for 2–72 h, then frozen at −20°C for 24–48 h and thereafter stored at −80°C.