The prevalence of C4d-positive renal allografts in 134 consecutive biopsies in Thai patients.

Antibody-mediated rejection (AMR) has been recognized recently as an important cause of graft failure. Detection of C4d in renal allograft biopsies is a proven ancillary technique in the diagnosis of AMR. The prevalence of C4d staining in Western countries varies from 17% to 60% among indication biopsies. There are only a few C4d prevalence studies in an Asian population. The objective of this study was to identify prevalence of C4d among Thai renal transplant patients. Consecutive renal allograft biopsies from 99 patients from 1999 to 2007 were stained for C4d by an immunoperoxidase technique. The biopsy slides were evaluated for the diagnosis according to the Banff'07 classification and histological scores. The relevant clinical data were obtained from clinical records. The prevalence of C4d in renal allografts was reported as a percentage using a descriptive analysis. Chi-square and unpaired Student t tests were used to evaluate the association between clinicopathologic findings and C4d positivity. P values less than .05 were considered significant. The prevalence of positive C4d staining was 16.4%. Fourteen biopsies (10.4%) showed diffuse staining while 8 (5.9%) revealed focal staining. Transplant glomerulopathy, glomerulitis, and peritubular capillaritis were associated with C4d positivity. Most inflammatory cells in peritubular capillaritis were mononuclear cells. Banff score elements, including tubulitis, intimal arteritis, interstitial infiltrate, interstitial fibrosis, tubular atrophy, mesangial matrix increase, vascular fibrous thickening, and arteriolar hyaline thickening, were not associated with C4d positivity. Many factors contribute to the varied prevalence of C4d positivity, including immunologic risks for AMR, type of allograft biopsy, and technique of C4d staining. Our study showed no difference in C4d prevalence among Thai renal allograft patients compared to the Western population. The suggestion to use C4d staining on all allograft biopsies should applied to Thai patients as well.