Quantification of LC3, p62, and TDP-43 positive fibers in the PM and IBM groups. The percentage of LC3- (a), p62- (c), and TDP-43-positive fibers (e) was significantly higher in the IBM group than the PM group. Each subject is represented with a symbol; the open symbols indicate subjects with known IBM clinical presentation. The unbroken lines designate group means, while dotted lines mark 100% sensitivity and 100% specificity cutoffs for each marker derived from ROC analysis. ****, p < 0.0001; **, p < 0.01. ROC analysis (b, d, and f) shows that quantitative immunohistochemistry for each of the three markers successfully differentiates IBM from PM subjects (p ≤ 0.001), although with varying tradeoffs between specificity and sensitivity. Of the three markers examined, only TDP-43 (f) failed to reach 100% sensitivity threshold, indicated by the dotted line in (f).