SPP1 and Pleural effusion: Furthermore, syndecan-1 and osteopontin levels correlated in both pleural effusions (r = 0.18, P = 0.019) and sera (r = 0.25, P < 0.0001; see Supplementary Figure S1 in Supplementary Material available online at http://dx.doi.org/10.1155/2014/419853).