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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
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P
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B
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**
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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