Performance of seven serological assays for diagnosing tularemia

BMC Infectious Diseases

Table 1 Performance of 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

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).
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.

ISSN: 1471-2334