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Table 1 Performance of serological assays for diagnosing tularemia

From: Performance of seven serological assays for diagnosing tularemia

  In-house ELISA In-house ELISA VIRapid WB Serazym ELISA Serion ELISA Serion ELISA Array
  Cut-off = 0.18 Cut-off = 0.33     IgG IgM  
True positive 129 118 131 126 131 130 128 123
False negative 6 17 4 9 4 5 7 12
False positive 22 12 15 16 8 3 3 2
True negative 72 82 79 78 86 91 91 92
Diagnostic sensitivity [%] 95.6 87.4 97.0 93.3 97.0 96.3 94.8 91.1
Diagnostic specificity [%] 76.6 87.2 84.0 83.0 91.5 96.8 96.8 97.9
PPV [%] 85.4 90.8 89.7 88.7 94.2 97.7 97.7 98.4
NPV [%] 92.3 82.8 95.2 89.7 95.6 94.8 92.9 88.5
Diagnostic accuracy [%] 87.8 87.3 91.7 89.1 94.8 96.5 95.6 93.9
  1. The following tests were evaluated: Western blot (WB); Serion ELISA classic Francisella tularensis IgG/IgM (Institut Virion\Serion GmbH, Würzburg, Germany) (IgG and IgM Serion ELISA); Serazym® Anti-Francisella tularensis (Seramun Diagnostica GmbH, Heidesee OT Wolzig, Germany) (Serazym ELISA); VIRapid® Tularemia (Vircell S.L., Santa Fé, Spain) (VIRapid); antigen microarray (array) and an in-house ELISA. (TP = true positive, TN = true negative, FN = false negative, FP = false positive).
  2. The diagnostic value was determined based on the following parameters: Diagnostic sensitivity = [TP/(TP + FN)] × 100; Diagnostic specificity = [TN/(TN + FP)] × 100; Positive Predictive Value (PPV) = [TP/(TP + FP)] × 100; Negative Predictive Value (NPV) = [TN/(TN + FN)] × 100; Diagnostic accuracy = (TP + TN)/(TP + TN + FP + FN)×100.