 Micro-centrifuge tubes, containing periopaper strips with absorbed GCF sample, were allowed to reach room temperature and eluted using a centrifugal method.17 After centrifugation, the strips were removed and the fluid was assayed by ELISA for N and soluble VCAM-1.The levels of N and sVCAM-1 in serum and GCF samples were measured using ELISA kit , . The ELISA procedures were carried out according to the manufacturers instructions. 