Cluster analysis based on changes in creatinine. A: Modified L'Abbé plot showing the results of model-based, unsupervised cluster analysis. Unlike Figure 5A, studies are unweighted for easier visualization. Cluster analysis (see the Methods section) applied to the 22 studies found two distinct populations of trials. Crosshairs and circles denote the mean ± SD of each cluster. B: Aggregate NAC treatment effect and heterogeneity analysis of each cluster. The entire group of 22 studies had unacceptable heterogeneity (I
2 = 37%; p = 0.04) making the summary point estimate unreliable (not shown). Cluster 1 (n = 18; 2445 patients) is homogeneous and shows no benefit (RR = 0.87; 95% CI 0.68–1.12, p = 0.28). Cluster 2 (N = 4; 301 patients) is also homogeneous and indicates that NAC is very beneficial (RR = 0.15; 95% CI 0.07–0.33, p < 0.0001).