SDC1 and cholesteryl ester measurement: Recent studies have used immunohistochemical methods to increase the accuracy of plasma cell counts further; CD138 (Syndecan-1) staining has been used in recent studies; CD-138 staining in 107 RPL patients found a significantly higher prevalence of CE compared to morphology and HE staining alone (56% vs. 13%, P < 0.01) [43].