Composite testing for ante-mortem diagnosis of Johne’s disease in farmed New Zealand deer: correlations between bacteriological culture, histopathology, serological reactivity and faecal shedding as determined by quantitative PCR

Table 2 Sensitivity and specificity values for Paralisa™ calculated using faecal qPCR as a gold standard

		Shedding Threshold for Positivity (organisms/g)
		≥10²	≥10³	≥10⁴	≥10⁵	≥10⁶	≥10⁷	≥10⁸
Paralisa Overall	Sens.	0.62	0.67	0.78	0.87	0.89	0.96	0.98
	Spec.	0.70	0.68	0.63	0.62	0.61	0.60	0.58
	PPV	0.70	0.61	0.41	0.35	0.31	0.26	0.20
	NPV	0.62	0.74	0.90	0.95	0.97	0.99	1.00
PPD-J EU >50	Sens.	0.46	0.52	0.70	0.82	0.84	0.91	0.94
	Spec.	0.85	0.84	0.81	0.81	0.79	0.78	0.75
	PPV	0.78	0.71	0.55	0.50	0.44	0.37	0.28
	NPV	0.58	0.70	0.89	0.95	0.96	0.98	0.99
PPD-J EU >100	Sens.	0.34	0.40	0.62	0.74	0.78	0.86	0.89
	Spec.	0.94	0.93	0.93	0.92	0.91	0.89	0.86
	PPV	0.87	0.82	0.73	0.67	0.62	0.53	0.40
	NPV	0.55	0.68	0.88	0.94	0.95	0.98	0.99
PPD-J EU >150	Sens.	0.24	0.29	0.48	0.60	0.64	0.75	0.81
	Spec.	0.98	0.98	0.98	0.97	0.96	0.96	0.93
	PPV	0.93	0.92	0.88	0.83	0.78	0.71	0.56
	NPV	0.53	0.65	0.85	0.91	0.93	0.96	0.98

Sensitivity (Sens.), specificity (Spec.), positive and negative predictive values (PPV and NPV, respectively) for Paralisa^TM to predict MAP shedding in deer as determined by qPCR. ‘Paralisa Overall’ indicates the final result when Johnin and Protoplasmic Antigen responses are interpreted in parallel; EU, ELISA Units.

ISSN: 1746-6148