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Table 2 Predictive algorithm outcomes using the random forest algorithm diagnostic characteristics

From: Protein oxidation, nitration and glycation biomarkers for early-stage diagnosis of osteoarthritis of the knee and typing and progression of arthritic disease

  Algorithm 1 Algorithm 2
Features Hyp and MetSO, DT, NFK, 3-NT, CEL, CMA, G-H1, MG-H1, 3DG-H and pentosidine anti-CCP antibody positivity and MetSO, DT, 3-NT, FL, CML, CEL, CMA, MG-H1, 3DG-H and pentosidine
Comparators Disease versus control eOA eRA non-RA
Training set cross-validation
 Correct, n 44/46 13/13 6/8 8/12
 Sensitivity 0.92 (0.64–1.00) 0.92 (0.64–1.00) 0.80 (0.44 - 0.97) 0.70 (0.35 - 0.93)
 Specificity 0.91 (0.76–0.98) 0.90 (0.68–0.99) 0.78 (0.56–0.93) 0.65 (0.43–0.84)
 AUROC 0.99 (0.97–1.00) 0.98 (0.96–1.00) 0.91 (0.82–1.00) 0.68 (0.49–0.86)
 Positive predictive value 1.0 1.0 0.60 0.80
 Negative predictive value 0.85 1.0 0.84 0.83
 Positive likelihood ratio 10.2 9.2 3.6 2.0
 Negative likelihood ratio 0.09 0.09 0.26 0.46
Test set cross-validation
 Correct, n 119/134 30/31 22/27 27/39
 Sensitivity 0.89 (0.75–0.97) 0.83 (0.65–0.94) 0.77 (0.6–0.9) 0.72 (0.53–0.86)
 Specificity 0.90 (0.82–0.95) 0.84 (0.73–0.92) 0.76 (0.63–0.86) 0.71 (0.58–0.81)
 AUROC 0.96 (0.93–0.99) 0.93 (0.88–0.98) 0.87 (0.8–0.94) 0.77 (0.68–0.86)
 Positive predictive value 0.96 0.97 0.81 0.69
 Negative predictive value 0.75 1.0 0.81 0.91
 Positive likelihood ratio 8.9 5.2 3.2 2.5
 Negative likelihood ratio 0.12 0.20 0.30 0.39
Test set validation
 Correct, n 63/134 18/19 8/35 31/32
 Sensitivity 0.73 (0.56–0.86) 0.83 (0.65–0.94) 0.60 (0.42–0.76) 0.81 (0.64–0.93)
 Specificity 0.72 (0.62–0.81) 0.84 (0.73–0.92) 0.61 (0.46–0.72) 0.80 (0.68–0.89)
 AUROC 0.77 (0.69–0.85) 0.91 (0.84–0.99) 0.62 (0.5–0.75) 0.84 (0.77–0.92)
 Positive predictive value 0.62 0.60 0.23 0.97
 Negative predictive value 0.05 0.99 0.97 0.43
 Positive likelihood ratio 2.6 5.2 1.5 4.1
 Negative likelihood ratio 0.38 0.20 0.67 0.24
  1. The 95 % CI for sensitivity and specificity are given in brackets. eOA early osteoarthritis, aOA advanced osteoarthritis, eRA early rheumatoid arthritis, aRA advanced rheumatoid arthritis, CML Nε-carboxymethyl-lysine, CEL Nε-carboxyethyl-lysine, MetSO methionine sulfoxide, DT dityrosine, FL Nε-fructosyl-lysine, MG-H1 methylglyoxal-derived hydroimidazolone, 3DG-H 3-deoxyglucosone-derived hydroimidazolone isomers, NFK N-formylkynurenine, 3-NT 3-nitrotyrosine, G-H1 glyoxal-derived hydroimidazolone, CMANω-carboxymethylarginine