Table 5.

The expected results of a hypothetical screening study for abdominal cystic echinococcosis using the VIRapid^® test alone (+/−), ultrasonography alone (+/−), or the sequential application of ultrasonography followed by the VIRapid test only in individuals with evocative ultrasound imaging.

VIRapid test alone				Ultrasonography alone				Ultrasonography followed by VIRapid test only in individuals with evocative abdominal lesions
Sensitivity		0.76		Sensitivity		0.98		Net sensitivity		0.74
Specificity		0.79		Specificity		0.96		Net specificity		0.99
True prevalence, 5%
	RDT+	RDT–	Total		US+	US–	Total		Test+	Test–	Total
CE pos	190	60	250	CE pos	245	5	250	CE pos	186	64	2,500
CE neg	998	3,753	4,750	CE neg	190	4,560	4,750	CE neg	40	4,710	4,750
Total	1,188	3,813	5,000	Total	435	4,565	5,000	Total	226	4,774	5,000
PPV		0.16 (0.15–0.17)		PPV		0.56 (0.55–0.58)		PPV on US+		0.82 (0.78–0.86)
NPV		0.98 (0.98–0.99)		NPV		0.99 (0.99–1.00)		NPV on US+		0.72 (0.67–0.76)
Estimated prevalence		23.8%		Estimated prevalence		8.7%		Estimated prevalence		4.52%
True prevalence, 1%
	RDT+	RDT–	Total		US+	US–	Total		Test +	Test -	Total
CE pos	38	12	50	CE pos	49	1	50	CE pos	37	13	50
CE neg	1,040	3,911	4,950	CE neg	198	4,752	4,950	CE neg	42	4.908	4.950
Total	1,078	3,923	5,000	Total	247	4,753	5,000	Total	79	4.921	5.000
PPV		0.03 (0.03–0.04)		PPV		0.20 (0.19–0.21)		PPV on US+		0.47 (0.41–0.53)
NPV		1.00 (0.99–1.00)		NPV		1.00 (0.99–1.00)		NPV on US+		0.93 (0.89–0.96)
Estimated prevalence		21.6%		Estimated prevalence		4.94%		Estimated prevalence		1.58%

CE = cystic echinococcosis; neg = negative; NPV = negative predictive value; pos = positive; PPV = positive predictive value; RDT–, negative VIRapid test; RDT+ = positive VIRapid test; US– = negative ultrasonography; Test– = negative evocative ultrasound imaging; Test+ = evocative ultrasound imaging; US+ = positive ultrasonography.