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

Q2: What are the best methods to identify a norovirus outbreak in a healthcare setting?

Evidence Table Q2 - Specimen collection

Author, Yr (Ref) Study Design Quality Study Objective Population and Setting N Results Comments Ref ID_Data extracted by
Duizer, E; 2007 117 Diagnostic study
 
2,3
To use statistical analysis in determining 1) the minimum number of positive stool samples using RTPCR or ELISA (IDEIA) compared to a hypothetical gold standard needed to declare norovirus as the causative agent of a gastroenteritis outbreak and 2) the probability of finding this minimum number of positive samples for varying numbers of tested samples. N/A # Positive samples needed to assign norovirus as the causative agent
 
ELISA:
1 positive for 2-6 samples tested
 
RT-PCR:
1 positive for 2-4 samples tested
2 positive for 5-11 samples tested
 
Sensitivity (%) for detecting a norovirus outbreak for various numbers of tested samples
ELISA:
57% for 2 tested samples
72% for 3 tested samples
88% for 5 tested samples
92% for 6 tested samples
 
RT-PCR:
84% for 2 tested samples
>90% for 3 tested samples
92% for 5 tested samples
96% sensitivity for 6 tested samples
Parameters
Defined outbreak as caused by norovirus if the prevalence is >8%
Hypothetical gold standard: sensitivity 100%; specificity 100%.
 
RT-PCR: sensitivity 72%; specificity 99%.
 
IDEIA: sensitivity 41%; specificity 98%.
 
Minimum # positive samples needed is the number of positive samples where there is >95% probability of attaining a prevalence ≥8%
 
IDEIA NLV (Dakocytomation Ltd., Ely, UK).
044_IL
Gray, JJ; 2007 118 Diagnostic study
 
2,3
To determine test characteristics for IDEIA and RIDA-SCREEN. Stool samples from patients with symptoms of gastroenteritis collected during the 2004-2005 and 2005-2006 norovirus seasons and evaluated in this European multicenter study.
 
2,254 samples from 273 outbreaks.
 
274 samples collected in sporadic cases.
 
144 samples had other enteric pathogens identified.
Test characteristics
IDEIA:
Sensitivity 58.93% (95% CI 56.12-61.68%)
Specificity 93.91% (95% CI 92.23-95.25%)
PPV 92.30%
NPV 64.90%
 
RIDA-SCREEN:
Sensitivity 43.81% (95% CI 41.01-46.65%)
Specificity 96.27% (95% CI 95.00-97.38%)
PPV 93.70%
NPV 58.20%
 
Sensitivity for differing number of samples tested
The sensitivity for outbreak diagnosis improved when ≥6 samples tested.
IDEIA: 3 vs. 6 samples tested (z=±3.191; p=0.0014) RIDA-SCREEN: 3 vs. 6 samples tested (z=±3.828; p=0.0001)
 
Range of norovirus genotypes detected
All samples: Genotype - IDEIA vs. RIDASCREEN No [(%) samples genotype detected (95% CI)]; p value
GI-1 – 4 [80.00% (37.55-96.36%)] vs. 3 [60.00% (23.07-88.24%)]; 0.49
GI-2 – 11 [84.62% (57.77-95.67%)] vs. 2 [15.38% (4.33-42.23%)]; 0.0002
GI-3 – 12 [42.86% (26.51-60.93%)] vs. 9 [32.14% (17.93-50.66%)]; 0.4
GI-4 – 2 [100.00% (34.24-100.00%)] vs. 0 [0.00% (0.00-65.76%)]; 0.3
GI-5 – 3 [37.50% (13.68-69.43%)] vs. 0 [0.00% (0.00-32.44%)]; 0.2
GI-6 – 5 [71.43% (35.89-91.78%)] vs. 0 [0.00% (0.00-35.43%)]; 0.02
GI-7 – 0 [0.00% (0.00-79.35%)] vs. 0 [0.00% (0.00-79.35%)]; >0.5
GII-1 – 7 [87.50% (52.91-97.76%)] vs. 0 [0.00% (0.00-32.44%)]; 0.0024
GII-2 – 8 [50.00% (28.00-72.00%)] vs. 4 [25.00% (10.18-49.50%)]; 0.2
GII-3 – 30 [57.69% (44.19-70.13%)] vs. 11 [21.15% (12.24-34.03%)]; 0.0003
GII-4 – 203 [67.44% (61.96-72.49%)] vs. 186 [61.79% (56.19-67.10%)]; 0.17
GII-5 – 2 [33.33% (9.68-70.00%)] vs. 3 [16.67% (3.01-56.35%)]; >0.5
GII-6 – 2 [22.22% (6.32-54.74%)] vs. 0 [0.00% (0.00-29.91%)]; 0.4
GII-7 – 20 [68.97% (50.77-82.72%)] vs. 5 [17.24% (7.6-34.55%)]; 0.002
GII-8 – 0 [0.00% (0.00-79.35%)] vs. 0 [0.00% (0.00-79.35%)]; >0.5
GIV-1 – 0 [0.00% (0.00-48.99%)] vs. 0 [0.00% (0.00-48.99%)]; >0.5
rGII – 10 [52.63% (31.71-72.67%)] vs. 2 [10.53% (2.94-31.39%)]; 0.01
 
IDEIA showed reactivity to a broader range of genotypes than the RIDASCREEN norovirus assay, which showed genotype-dependent sensitivities.
IDEIA norovirus (Oxoid; Thermo Fisher Scientific, Ely, UK). RIDASCREEN norovirus (R-Biopharm, Darmstadt, Germany) RT-PCR was the reference standard. 053_IL
Richards, A; 2003 119 Diagnostic Study
 
1,2
To determine the test characteristics of ELISA and EM in detecting norwalk-like virus (NLV) infection when compared with PCR Fecal samples collected from patients involved in outbreaks of gastroenteritis in the UK
 
531 fecal samples
Test characteristics (%) of ELISA vs. PCR
Sensitivity – 55.5(51.1-60.0)
Specificity – 98.3(97.1-99.9)
PPV – 95.0(CI not reported)
NPV – 76.9 (CI not reported)
 
Test characteristics (%) of EM vs. PCR
Sensitivity – 23.9(19.5-28.1)
Specificity – 99.2(98.3-100)
PPV – 93.9(CI not reported)
NPV – 70.7(CI not reported)
 
Identification of NLV as the cause of an outbreak (% of outbreaks)
When the causative agent was defined by ≥ 2 positive samples
EM – 7.2
ELISA – 18.6
PCR – 41.5
When the causative agent was defined by ≥ 1 positive samples
EM – 19.6
ELISA – 47.8
PCR – 62.8
 
Sensitivity; Specificity of ELISA based on number of samples collected
2 samples – 52.9; 100
≥4 – 69.2; 100
≥6 – 71.4; 100
 
Other results
Agreement between ELISA and PCR – 81.8% (Kappa = 0.57)
Sensitivity of ELISA was significantly increased when compared with EM (P<0.01)
Power and sample size not reported. 848_RA

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