Guideline for the Prevention and Control of Norovirus Gastroenteritis Outbreaks in Healthcare Settings, 2011

GRADE Table Q2 What Are The Best Methods To Identify A Norovirus Outbreak In A Healthcare Setting?

Person characteristics

Demographic characteristics

Comparison	Outcome	Quantity and type of evidence	Findings	Starting grade	Decrease GRADE					GRADE of Evidence for Outcome	Overall GRADE of Evidence Base
					S t u d y   Q u a l i t y **	C o n s i s t e n c y **	D i r e c t n e s s **	P r e c i s i o n **	P u b l i c a t i o n   B i a s **
Kaplan criteria	Sensitivity*	1 DIAG 116	68%	High	0	0	0	−1	0	Moderate	Moderate
	Specificity*	1 DIAG 116	99%	High	0	0	0	−1	0	Moderate
	PPV*	1 DIAG 116	97%	High	0	0	0	−1	0	Moderate
	NPV*	1 DIAG 116	82%	High	0	0	0	−1	0	Moderate
Specimen collection	Number of positive samples needed*	1 DIAG 117	Using ELISA, 1 positive sample for 2-6 samples tested was needed to assign norovirus as the causative agent Using RT-PCR, 1 positive sample for 2-4  samples tested or 2 positive samples for 5-11 samples tested were needed to assign norovirus as the causative agent	High	−1	0	0	−1	0	Low	Low
	Sensitivity*	2 DIAG 117 ,119	ELISA: 2 tested samples – 53-57%; 3 tested samples – 72%; ≥4 tested samples – 69%; 5 tested samples – 88%; 6 tested samples – 92%; ≥6 tested samples – 71% RT-PCR: 2 tested samples – 84%; 3 tested samples – >90%; 5 tested samples – 92%; 6 tested samples – 96%	High	−1	0	0	0	0	Moderate
	Specificity*	1 DIAG 119	ELISA: 2 to ≥6 samples – 100%	High	−1	0	0	−1	0	Low

* These outcomes are considered the most critical by the guideline developers.
** These modifiers can impact the GRADE by 1 or 2 points

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