Higher anti-HLA Ab NBG ratios are associated with refractoriness among LCA⁺ recipients. Peak class I (A) and class II (B) HLA Ab NBG ratios and normalized maximum absorbance values for HPA Abs (D) were compared between CR⁻ and CR⁺ LCA⁺ recipients. The dashed lines mark the cutoff used to distinguish positive and negative results; mean values were compared using a 1-tailed unpaired t-test. *P < .05. (C) Class I HLA Ab NBG ratios were log₁₀ transformed and plotted against class II HLA Ab NBG ratios, and correlation was evaluated. Error bars display mean and standard error.