HLA-G and kidney disorder: A limitation of this study was our inability to adjust for biomarkers of renal tubular impairment in the primary analysis and to precisely adjust for Cd-induced tubular kidney damage in the secondary analysis, in which participant-reported physician diagnosis of kidney disease provided a weak surrogate relative to tubular dysfunction biomarkers such as retinol-binding protein (Schutte et al. 2008) and β2-microglobulin (Chen et al. 2006).