Type IV Collagen Variants in CKD: Performance of Computational Predictions for Identifying Pathogenic Variants

Abstract Rationale & Objective: Pathogenic variants in type IV collagen have been reported to account for a significant proportion of chronic kidney disease. Accordingly, genetic testing is increasingly used to diagnose kidney diseases, but testing also may reveal rare missense variants that are of uncertain clinical significance. To aid in interpretation, computational prediction (called in silico) programs may be used to predict whether a variant is clinically important. We evaluate the performance of in silico programs for COL4A3/A4/A5 variants. Study Design, Setting & Participants: Rare missense variants in COL4A3/A4/A5 were identified in disease cohorts, including a local focal segmental glomerulosclerosis (FSGS) cohort and publicly available disease databases, where they are categorized as pathogenic or benign based on clinical criteria. Tests Compared and Outcomes: All rare missense variants identified in the four disease cohorts were subjected to in silico predictions using 12 different programs. Comparisons between the predictions were compared to: 1. variant classification (pathogenic or benign) in the cohorts; and 2. functional characterization in a randomly selected smaller number (17) of pathogenic or uncertain significance variants obtained from the local FSGS cohort. Results: In silico predictions correctly classified 75-97% of pathogenic and 57-100% of benign COL4A3/A4/A5 variants in public disease databases. Congruency of in silico predictions were similar for variants categorized as pathogenic and benign, with the exception of benign COL4A5 variants, in which disease effects were overestimated. By contrast, in silico predictions and functional characterization classified all 9 pathogenic COL4A3/A4/A5 variants correctly that were obtained from a local FSGS cohort. These programs, however, also overestimated the effects of genomic variants of uncertain significance when compared to functional characterization. Each of the 12 in silico programs used yielded similar results. Limitations: Overestimation of in silico program sensitivity given that they may have been used in the categorization of variants labelled as pathogenic in disease repositories. Conclusion: Our results suggest that in silico predictions are sensitive but not specific to assign COL4A3/A4/A5 variant pathogenicity, with misclassification of benign variants and variants of uncertain significance. Thus, we do not recommend in silico programs but instead recommend pursuing more objective levels of evidence suggested by medical genetics guidelines.