Diagnostic accuracy of perforin expression for detecting biallelic PRF1 mutations. (A) Sensitivity/specificity/PPV/NPV of low perforin MCF to distinguish biallelic PRF1 mutations from all other sequencing results. (B) Sensitivity/specificity/PPV/NPV of low perforin MCF to distinguish biallelic PRF1 mutation from patients with normal sequencing results. (C) Distribution of perforin MCF results among patients with no mutations, 1 or more VUCS (including A91V mutations), patients with A91V VUCS, carriers (with or without additional VUCS), and patients with biallelic mutations. (D) ROC curve showing diagnostic accuracy of perforin MCF to distinguish patients with biallelic PRF1 mutations compared with patients with all other sequencing results; sensitivity and specificity are shown at the optimal diagnostic cutoff of perforin MCF ≤ 38.