The RIDASCREEN® Norovirus 3td Generation test is a qualitative enzyme immunoassay (EIA) intended for the detection of selected genogroup I (GI.1, GL.2, GI.3, GI.4, GL.7) and genogroup II (GII.1, GII.2, GII.3, GII.4, GII.5, GII.6, GII.7, GII.8, GII.10, GII.12, GII.13, GII.14, GII.17) norovirus strains in human feces as an aid in investigating the cause of acute gastroenteritis outbreaks. The likelihood of detecting a norovirus outbreak by use of the RIDASCREEN® Norovirus 3td Generation test improves as the number of patients tested during an outbreak increases, as well as when quality of the specimens increases. Preliminary identification of norovirus as the cause of an acute gastroenteritis outbreak by RIDASCREEN® Norovirus 3td Generation testing should be confirmed by reference methods as appropriate, particularly if only a limited number of positive samples are associated with a suspected outbreak. Additional testing of negative samples by other methods should be performed if norovirus is strongly suspected as the cause of an acute gastroenteritis outbreak.

Device Description

RIDASCREEN® Norovirus 3rd Generation test is a solid phase sandwich-type EIA for the detection of genogroups GI and GII noroviruses in stool samples. Microwell strips are coated with a mixture of GI and GII norovirus specific monoclonal antibodies. An aliquot of fecal suspension is added to the microwell together with biotinylated monoclonal norovirus antibodies. After washing, streptavidin peroxidase conjugate is added. Norovirus antigens that are present in the stool sample are captured in a sandwich complex of the immobilized antibodies, the norovirus antigens and the monoclonal antibodies conjugated with the biotin-streptavidin-peroxidase complex. Unbound streptavidin peroxidase conjugate is removed by washing and a chromogenic colorless substrate solution (hydrogen peroxide/TMB) is added. The substrate is hydrolyzed by any bound peroxidase, changing the chromogen to a blue color. Stopping the reaction with acid converts the blue to a yellow color indicating the presence of norovirus antigens.

Test results are read photometrically; intensity significantly above background levels is indicative of the presence of Norovirus antigen in the specimen or control. The RIDASCREEN® Norovirus 3rd Generation test does not identify specific norovirus strains.

AI/ML Overview

Here's an analysis of the provided text, extracting the requested information about acceptance criteria and the device study:

1. A table of acceptance criteria and the reported device performance

The document does not explicitly state formal "acceptance criteria" against which the device's performance was measured. Instead, it reports the device's performance characteristics. If we were to infer acceptance criteria from the reported performance in the Overall Clinical Trial, a reasonable interpretation would be the achieved positive agreement and negative agreement.

Inferred Acceptance Criteria (based on reported performance):

Performance Metric	Inferred Acceptance Criteria	Reported Device Performance
Positive Agreement (PPA)	Acceptable if ≥ 59%	65% (95% CI: 59 - 71%)
Negative Agreement (NPA)	Acceptable if ≥ 86%	90% (95% CI: 86 - 93%)

2. Sample size used for the test set and the data provenance (e.g. country of origin of the data, retrospective or prospective)

Sample Size (Test Set): 609 samples (after excluding 69 invalid samples and 2 equivocal samples from an initial collection of 680).
Data Provenance:
- Country of Origin: Three sites in the United States (Ohio, California, Cincinnati) and one site in Canada (Hamilton, Ontario).
- Retrospective or Prospective: Prospective (samples were collected from patients presenting with acute gastroenteritis symptoms).

3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts (e.g. radiologist with 10 years of experience)

The ground truth for the test set was established using a "Clinical Diagnostic Truth" algorithm based on a composite reference endpoint, not directly by experts. The reference methods included:

Quantitative real-time RT-PCR (qRT-PCR)
Conventional RT-PCR with bi-directional sequencing (Region D and Region B)
Electron Microscopy (EM)

While these methods would be performed by trained laboratory personnel, the document does not specify the number or qualifications of experts (e.g., virologists, molecular biologists) who established the final "Clinical Diagnostic Truth." However, the reference testing was conducted at established public health and disease control laboratories: the California Dept. of Public Health (CPDH) and the National Calicivirus Laboratory, Centers for Disease Control and Prevention (CDC).

4. Adjudication method (e.g. 2+1, 3+1, none) for the test set

The ground truth was established by a rule-based algorithm, not an adjudication process involving multiple human readers in the traditional sense. The algorithm for "Clinical Diagnostic Truth" considered a sample positive if it was positive by:

Region D RT-PCR OR
Region B RT-PCR OR
Electron Microscopy (EM)

If all three methods were negative, the sample was considered negative. There was an initial "Original Composite 'Clinical Diagnostic Truth' Algorithm" that included qRT-PCR, but this was revised due to concerns, and the final algorithm focused on Region D RT-PCR, Region B RT-PCR, and EM.

5. If a multi reader multi case (MRMC) comparative effectiveness study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance

No, a multi-reader multi-case (MRMC) comparative effectiveness study was not done. This device is a diagnostic immunoassay for Norovirus detection, not an AI-assisted diagnostic tool designed to be used by human readers (like a radiologist reading an AI-analyzed image). Therefore, the concept of human readers improving with/without AI assistance does not apply.

6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done

Yes, the study primarily focused on standalone performance of the RIDASCREEN® Norovirus 3rd Generation EIA. The device is a qualitative enzyme immunoassay that provides a positive or negative result. The "Overall Clinical Trial Performance" table directly compares the results of the RIDASCREEN® assay against the "Clinical Diagnostic Truth" reference standard. There is no indication of human interpretation influencing the ELISA's output or any human-in-the-loop step being assessed as part of its performance.

7. The type of ground truth used (expert consensus, pathology, outcomes data, etc)

The ground truth used was a composite reference standard (referred to as "Clinical Diagnostic Truth"). This was established through a combination of molecular assays (conventional RT-PCR with bi-directional sequencing for regions B and D, and quantitative real-time RT-PCR initially) and electron microscopy (EM). This is a laboratory-based, objective ground truth, which is often considered highly reliable for viral detection.

8. The sample size for the training set

The document does not explicitly mention a "training set" in the context of device development or a formal machine learning model. For this device, an immunoassay, the concept of a "training set" as understood in AI/ML is not directly applicable. Performance characteristics (like precision, detection limit, cross-reactivity, and strain reactivity) were evaluated using panels of samples, but these are typically part of analytical validation rather than training a model.

The "Strain-reactivity" section mentions the sponsor studied 100 archived samples (80 positive across different genotypes, 10 negative, 10 other viruses) but this was for analytical characterization, not model training.

9. How the ground truth for the training set was established

As there's no explicitly defined "training set" in the AI/ML sense, a ground truth establishment method for it isn't described. For the analytical studies (e.g., LoD, strain reactivity) that used well-characterized samples, the ground truth was based on known viral concentrations or confirmed genotypes through methods like conventional RT-PCR followed by sequencing and electron microscopy.

Summary

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510(k) SUBSTANTIAL EQUIVALENCE DETERMINATION DECISION SUMMARY

A. 510(k) Number:

K093295

B. Purpose for Submission:

Substantial equivalence determination for a new device

C. Measurand:

Norovirus, genogroup 1 and genogroup 2.

D. Type of Test:

Qualitative enzyme immunoassay

E. Applicant:

R-Biopharm AG An der neuen Bergstraße 17 64297 Darmstadt Germany

F. Proprietary and Established Names:

RIDASCREEN® Norovirus 3rd Generation EIA

G. Regulatory Information:

1. Regulation section: 21 CFR 866.3395
1. Classification: Class: II (de novo)
1. Product code: OUC (Norovirus serological reagent)
1. Panel: 83- Microbiology

H. Intended Use:

1. Intended use(s):
  The RIDASCREEN® Norovirus 3td Generation test is a qualitative enzyme immunoassay (EIA) intended for the detection of selected genogroup I (GI.1, GL.2, GI.3, GI.4, GL.7) and genogroup II (GII.1, GII.2, GII.3, GII.4, GII.5, GII.6, GII.7, GII.8, GII.10, GII.12, GII.13, GII.14, GII.17) norovirus strains in human feces as an aid in investigating the cause of acute gastroenteritis outbreaks. The likelihood of detecting a norovirus outbreak by use of the RIDASCREEN®

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Norovirus 3td Generation test improves as the number of patients tested during an outbreak increases, as well as when quality of the specimens increases. Preliminary identification of norovirus as the cause of an acute gastroenteritis outbreak by RIDASCREEN® Norovirus 3td Generation testing should be confirmed by reference methods as appropriate, particularly if only a limited number of positive samples are associated with a suspected outbreak. Additional testing of negative samples by other methods should be performed if norovirus is strongly suspected as the cause of an acute gastroenteritis outbreak.

1. Indication(s) for use:
  Identical to intended use
1. Special conditions for use statement(s): For prescription use
  .
  .
  .
1. Special instrument requirements: None

I. Device Description:

J. Substantial Equivalence Information:

1. Predicate device name(s): None
1. Predicate 510(k) numbers: None
1. Comparison with predicate: Not applicable

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K. Standard/Guidance Document Referenced (if applicable):

A special control guidance document will be promulgated.

L. Test Principle:

Enzyme immunoassay

M. Performance Characteristics:

1. Analytical performance:

a. Precision/Reproducibility:
- i. Inter-assay reproducibility:

Inter-assay precision was studied with 6 fecal samples run in triplicates on 10 consecutive days by three different operators using 3 separate test kits.

		Sample 1HighPositive	Sample 2MediumPositive	Sample 3MediumPositive	Sample 4LowPositive	Sample 5LowPositive	Sample 6Negative
Min/maxStandard[OD450]		1.303/2.420	0.811/1.506	0.568/1.088	0.499/0.927	0.392/0.728	0.000/0.200
Kit 1		1.533	1.108	0.882	0.616	0.460	0.085
	SD	0.179	0.084	0.142	0.062	0.058	0.024
	CV	11.66%	7.55%	16.09%	10.11%	12.54%	28.02%
Kit 2		1.690	1.181	0.920	0.705	0.506	0.092
	SD	0.124	0.070	0.088	0.119	0.051	0.019
	CV	7.33%	5.89%	9.53%	16.93%	10.04%	20.45%
Kit 3		1.716	1.213	0.924	0.666	0.492	0.084
	SD	0.181	0.113	0.158	0.080	0.077	0.018
	CV	10.53%	9.28%	17.10%	12.08%	15.66%	20.86%

Inter-assay Reproducibility (Results reported are for Total Precision)

ii. Intra-assay reproducibility:

Intra-assay precision was determined by measuring 40 replicates of six fecal samples within one assay run. The accepted OD levels of the samples are listed below. Positive and negative controls were measured in triplicates each run, and three independent kit lots were tested. Mean values, standard deviations and coefficients of variance (CV) are summarized below.

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		Sample 1HighPositive	Sample 2MediumPositive	Sample 3MediumPositive	Sample 4LowPositive	Sample 5LowPositive	Sample 6Negative
Min/maxStandard[OD450]		1.172/2.176	1.001/1.859	0.737/1.369	0.484/0.900	0.284/0.527	0.000/0.200
Kit 1		1.653	1.205	1.014	0.563	0.309	0.051
	SD	0.042	0.114	0.034	0.021	0.016	0.002
	CV	2.54%	9.48%	3.39%	3.80%	5.16%	4.35%
Kit 2		1.643	1.198	1.012	0.561	0.308	0.051
	SD	0.041	0.114	0.035	0.021	0.016	0.002
	CV	2.50%	9.50%	3.42%	3.72%	5.14%	4.41%
Kit 3		1.481	0.953	1.006	0.559	0.307	0.051
	SD	0.101	0.066	0.035	0.021	0.016	0.003
	CV	6.81%	6.92%	3.43%	3.78%	5.19%	5.11%

Intra-assay Reproducibility (Results Reported are for Total Precision)

iii. Inter-lot reproducibility:

Inter-lot reproducibility was determined with three kits, each tested in triplicate over 10 days. As part of the inter-assay reproducibility study reported above. The following results are from the same data analyzed across kits:

Inter-lot Reproducibility (Results reported are for Total Precision)

	Sample1HighPositive	Sample 2MediumPositive	Sample3MediumPositive	Sample4LowPositive	Sample5LowPositive	Sample6Negative
No. Days	10	10	10	10	10	10
No. Results	90	90	90	90	90	90
No. KitLots	3	3	3	3	3	3
Total precision:Mean value[OD450]	1.646	1.167	0.909	0.662	0.486	0.087
SD	0.185	0.103	0.133	0.098	0.065	0.020
CV	11.23%	8.82%	14.60%	14.84%	13.33%	23.26%

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b. Linearity/assay reportable range:
Not applicable
c. Traceability, Stability, Expected values (controls, calibrators, or methods):
The sponsor conducted LoD validation of their Region B and region D conventional PCR assays using Norovirus positive samples of known viral concentrations. Serial dilution testing of G1.3b. G1.7, GII.3, and GII.4 containing stool samples using the sponsor's conventional Region B and Region D PCR assays estimated assay sensitivity at between 1 - 100 copies/ul for all strains, or approximately 250 - 3.500 mean copies/gm of stool. Additional strain reactivity studies examining Genogroup I: GI.2, GI.3b, GI.4, G1.6, G1.8, and Genogroup II: GII.1-4, GII.6, GII.7, GII.12, GII.14, GII.16, GII.17 samples found similar sensitivity using the Region D and region B assays, with the exception of GII.16 and GII.17, where sensitivity was approximately 1 - 2 logs less. Region B and region D conventional PCR sensitivities were similar (i.e., within 1 - 2 logs) for each strain tested with the exceptions of GII.14 and GII.17 which differed between the two assays by three logs: in both cases Region B conventional PCR was more sensitive than Region D testing. The sensitivity from combined use of the Region B and Region D assays was deemed acceptable for use as a reference standard for the clinical studies.
d. Detection limit:
The limit of detection was determined by conventional RT-PCR followed by bi-directional sequencing for norovirus regions B and Region D, and for electron microscopy. One GI.1 and one GII.4 isolate were studied. Results were reported as follows:

Genotype	Dilution	RIDASCREEN®Norovirus 3rdGeneration ELISA	ConventionalRT-PCR	Real-timeRT-PCR	EM
		Result	Result	Genomiccopies per g	Particles perg**
	1x100 *	positive	positive	1.10E+08	2.9E+08
	1x101	positive	positive	5.78E+07	3.5E+07
	1x102	positive	positive	5.45E+06	2.4E+07
GI.1	1x103	negative	positive	6.70E+05	negative
	1x104	negative	positive	1.24E+05	n/a
	1x105	negative	positive	negative	n/a
	1x106	negative	positive	negative	n/a
GII.4	1x100 *	positive	positive	1.91E+09	4.7E+08
	1x101	positive	positive	7.35E+08	5.9E+07

Limit of Detection

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$1x10^2$	positive	positive	2.89E+07	1.6E+07
$1x10^3$	negative	positive	6.65E+05	negative
$1x10^4$	negative	positive	negative	n/a
$1x10^5$	negative	positive	negative	n/a
$1x10^6$	negative	negative	negative	n/a

1x10º equals 20% dilution

** Genomic copies per gram and number of viral particles in the native fecal samples were calculated back from each positive dilution and the mean values are presented here

Stability: e.
Stability was assessed by kit for 3 lots against a panel including positive and negative controls, and 4 samples with different norovirus OD readings. Analyte stability was tested after sample freeze/thawing, in suspension ('ready to use'), and transport (shipping of samples internationally). Overall, decrement in OD values for positive samples at 12 months was < 20%.

Sample	Mean OD0 Months	Mean OD12 Months	%Decrease
#1	1.686	1.382	-18.0
#2	1.416	1.093	-22.8
#3	1.113	0.926	-16.8
#4	0.719	0.555	-22.8
#5	0.602	0.487	-19.0
#6	0.333	0.294	-11.5

Stability Testing Over 12 Months

Analytical specificity: f.

i. Cross-reactivity:

Cross-reactivity was assessed for the following:

Bacteria: Acinetobacter iwoffi. Aeromonas hydrophila aerogenes, Aeromonas hydrophila hydrophila, Campylobacter coli, Campylobacter fetus, Campylobacter jejuni. Citrobacter freundii, Clostridium difficile, Clostridium perfringens, Clostridium sordellii, Enterobacter cloacae, Enterococcus faecalis, Enterococcus faecium, E. coli, E. coli (0157:H-), E. coli (0116:H21), E. coli (0111:H-), E. coli (022:H8), E. coli (026:H11), Escherichia hermannii, Helicobacter pylori, Lactococcus lactis, Listeria innocua, Morganella morganii, Proteus mirabilis, Proteus vulgaris. Providencia stuartii, Pseudomonas aeruginosa, Pseudomonas fluorescens, Pseudomonas putida, Salmonella agona, Samonella choleraesuis, Salmonella enteritidis, Salmonella infantis, Salmonella Ohio, Salmonella typhimurium, Serratia proteamaculans (liquefaciens), Shigella flexneri, Shigella sonnei,

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Staphylococcus aureus, Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus uberis

Fungi: Candida albicans

Toxins: Shigatoxin STX, Shigatoxin STX2

Amoeba/Parasites: Cryptosporidium parvum, Entamoeba histolytica, Giardia lamblia

Viruses: Astrovirus, Adenovirus, Rotavirus, Sapovirus

No cross-reactivity was seen for any of the bacteria, viruses, toxins, for fungi tested.

ii. Interfering substances
Interference was checked with the following substances spiked into a negative and a positive specimen and then measured in triplicate.

Substance	Concentration
Mucin	5 % (w/w)
Human blood	5 % (v/w)
Barium sulfate (contrast medium)	5 % (w/w)
Loperamide (anti-diarrhea drug)	5 % (w/w)
Pepto-Bismol (anti-diarrhea drug)	5 % (v/w)
Stearic acid / Palmitic acid (1:1) (fatty acids)	40 % (w/w)
Metronidazole (0.5) (antibiotic)	5 % (v/w)
Diclofenac (analgesic)	0.00263 % (v/w)
Cyclamate (artificial sweetener)	5 % (v/w)

Substances Tested for Interference

No of interference was seen for any of the substances tested.

g. Assay cut-off:

Assay cut-off is established by adding 0.15 OD units to negative controls for each run; the 0.15 addition is based on the mean OD for negative samples (Limit of Blank) plus 5 x the standard deviation for negative and low analyte samples. Samples are considered positive if the OD is > 10% above the cut-off and negative if > 10% below the cut-off. Values between these two limits are considered equivocal and the test repeated.

The following are the results for 100 negative stool isolates tested by the sponsor, sorted in ascending order: 98/100 were below <0.075, with one value at 0.098 and 0.132 each.

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Image /page/7/Figure/0 description: This image is a bar graph. The x-axis ranges from 1 to 97 in increments of 4. The y-axis ranges from 0 to 0.14 in increments of 0.02. The bars are mostly at a value of around 0.04, but there is a spike at around 91, and then the bars return to a value of around 0.04.

h. Strain-reactivity:
There are 5 norovirus Genogroups (GI – V); human disease has only been identified in groups I, II, and IV; Genogroup IV-associated disease is uncommon and has been only observed outside the US.

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Image /page/8/Figure/0 description: This image shows a phylogenetic tree with different genotypes of norovirus. The tree is divided into five main branches, labeled GI, GII, GIII, GIV, and GV. Each branch represents a different genogroup, with GI being human, GII being human and swine, GIII being bovine, GIV being human and canine, and GV being murine. The tree shows the evolutionary relationships between different strains of norovirus, with the length of the branches indicating the degree of genetic divergence.

(Reproduced from Patel et al., Journal of Clinical Virology 44 (2009) 1-8.)

The sponsor studied 100 archived samples that included 80 samples across different genotypes from Genogroups I and II, 10 negative samples, and 10 other viruses. Results are summarized below:

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Sample tested	Number	#positive/#tested
Genogroup I
1	2	2/2
2	2	1/2
3	3	1/3
4	3	0/3
5	4	0/4
6	2	0/2
7	2	2/2
8	2	0/2
Genogroup II
1	3	2/3
2	4	3/4
3	8	7/8
4	16	16/16
5	5	3/5
6	5	1/5
7	4	4/4
8	3	3/3
9	1	0/1
10	1	1/1
12	3	1/3
13	2	1/2
14	2	1/2
16	1	0/1
17	2	1/2
Other viruses
Sapovirus	3	0/3
Rotavirus	3	0/3
Astrovirus	2	0/2
Enterovirus	2	0/2
Negative	10	0/10

Noroviruses Genotypes Samples for Strain Reactivity

2. Comparison studies:

a. Method comparison with predicate device:

There is no predicate device for Norovirus detection; following pre-IDE discussions with FDA/DMD, a composite reference endpoint of quantitative real time RT-PCR (qRT-PCR), conventional RT-PCR with bi-directional sequencing, with a subset of samples undergoing electron microscopy (EM), was agreed to. Specimens positive by either conventional RT-PCR (region D + sequencing) or Electron Microscopy were considered 'Clinical Diagnostic Truth' positive. The following table describes the original algorithm for establishing the reference standard:

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Real-timeRT-PCR	Conventional RT-PCR(region D + sequencing)	EM(with and without)	Clinical DiagnosticTruth
positive	positive	positive	positive
positive	positive	negative	positive
positive	positive	-	positive
negative	positive	positive	positive
negative	positive	negative	positive
negative	positive	-	positive
positive	negative	positive	positive
positive	negative	negative	Indeterminate*
positive	negative	-	Indeterminate*
negative	negative	positive	positive
negative	negative	negative	negative
negative	negative	-	negative

Original Composite 'Clinical Diagnostic Truth' Algorithm

- For indeterminate results, an additional conventional RT-PCR of Region-B followed by bi-directional sequence analysis was performed; clinical diagnostic truth was then determined on the basis of this result.

However, due to concerns regarding the execution of the real-time reverse transcriptase assay at the sponsor's clinical site, it was agreed that the sponsor would perform Region B RT-PCR testing on all Region D RT-PCR negative samples and that a revised 'Clinical Diagnostic Truth' algorithm would be used: in the revised algorithm, samples that were positive by either Region D RT-PCR, Region B RT-PCR, or Electron Microscopy were classified as 'Clinical Diagnostic Truth' positive.

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Region DRT-PCR	Region BRT-PCR	EM(with and without)	Clinical DiagnosticTruth
positive	-	positive	positive
positive	-	negative	positive
positive	-	-	positive
positive	-	positive	positive
positive	-	negative	positive
positive	-	-	positive
negative	positive	positive	positive
negative	positive	negative	positive
negative	positive	-	positive
negative	negative	positive	positive
negative	negative	negative	negative
negative	negative	-	negative
negative	positive	positive	positive
negative	positive	negative	positive
negative	positive	-	positive
negative	negative	positive	positive
negative	negative	negative	negative
negative	negative	-	negative

Revised 'Clinical Diagnostic Truth' Algorithm

b. Matrix comparison:
Not applicable.

3. Clinical studies:

a. Clinical Protocol
Clinical Trial Protocol 001-07: ELISA for Detection of Norovirus Antigens in Stool, Version 2.3.

i. Main Objectives

The protocol main objectives were listed as follows:

a. Primary objective:
To evaluate the sensitivity and specificity of the R-Biopharm Norovirus test for the detection of GI and GII viruses using stool samples from outbreaks or sporadic cases of gastroenteritis.
b. Secondary objectives:
- . To evaluate predictive values
- To verify cut-off values .

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Sampling of supportive clinical data (subject age, gender, geographic . region, duration of illness before collection of stool sample, vomiting, diarrhea) and evaluate influence on diagnostic accuracy.
A minimum of 410 specimens were to be collected.

ii. Major Inclusion/Exclusion Criteria

Major inclusion criteria included:

Stool specimen (non-bloody after visual inspection) submitted for . gastroenteritis testing
Patient information: age and gender, date of specimen collection if . available symptoms and signs of gastroenteritis (e.g., fever, vomiting, diarrhea (presence or absence, frequency), nausea, abdominal cramps and other symptoms)

Major exclusion criteria included:

No date of stool collection OR date of initial onset of symptoms . provided
Days from onset of symptoms to stool collection more then three • days
b. Clinical Sensitivity and Specificity:
- i. Overall Performance

The study was conducted at four sites (three in the United States and one in Canada). Samples were collected from patients with diarrhea and vomiting; subject selection was described as follows:

Specimens were be from patients (inpatient/outpatient, nursing homes occupants, various party attendees, conference attendees, restaurant guests and children) with signs and symptoms of acute gastroenteritis who are having samples submitted for diagnostic testing and for which there is at least 2.0 ml or gram residual stool for performance of the ELISA and reference assays.

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Clinical Study Sites
Site	Loc.	N	NorovirusELISA	RT-PCRSequencing	EM
1	Ohio Dept. of Health,Columbus, OH	200	Performedon site	Performed atCalif. Dept.Of PublicHealth(CPDH)	National CalicivirusLaboratory, Centersfor Disease Controland Prevention(CDC)
2	California Dept. ofPublic Health,Richmond, CA	214	Performedon site	Performed atCPDH	Performed at CDC
3	Cincinnati Children'sHospital MedicalCenter, Cincinnati, OH	211	Performedon site	Performed atCPDH	Performed at CDC
4	St. Joseph'sHealthcare, Hamilton,Ontario	55	Performedon site	Performed atCPDH	Performed at CDC
Total		680

Of the 680 samples collected, 69 were reported as invalid: 54 for 'no result' (although this described as the sponsor as not qualified by weight or volume), 10 with a missing PCR result, and 5 with a PCR result but no ELISA. Two equivocal samples were excluded from analysis. Overall results were reported for these 609 samples.

Overall performance results as follows: 1

		Presence of Norovirus("Clinical Diagnostic Truth")
		+	-	Total
RIDASCREEN	+	159	37	196
Result	-	85	328	413
Total		244	365	609

Positive agreement (95% CI)		65 % (59 - 71 %)
Negative agreement (95% CI)		90 % (86 - 93 %)

Overall Clinical Trial Performance

Ninety-seven samples were studied by EM; of n = 34 PCR (+) samples, 4 were EM positive and 24 ELISA positive. Of n = 59 disease negative samples, none were EM positive but 11/59 were ELISA (+).

1 Of the two equivocal sample was Clinical Diagnostic Truth (+) and the other (-).

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ii. Sensitivity for specific Norovirus strains (strain reactivity)

As noted earlier, the RIDASCREEN® Norovirus 3rd Generation assay shows differential sensitivity across norovirus genotypes. The sponsor reports that 167 'PCR positive' specimens were analyzed for genogroup/subtype with the following results:

Genogroup I			Genogroup II
Subtype	No. of PCR positive samples	No. of samples detected by ELISA	Subtype	No. of PCR positive samples	No. of samples detected by ELISA
2	2	1	1	1	1
3	10	2	3	3	3
3b	2	0	4	123	96
4	8	6	7	1	1
5	1	0	Unable to type	5	4
Unable to type	11	0

Clinical Genotypes Detected

The performance was better in the archived, higher inoculum wellcharacterized specimens described earlier relative to clinical specimens; several strains were not detected in the archived panel, e.g., GI.1, GI7, GI.8, and GII.9, and limited detection of others, e.g., only 1/5 GII.6 samples were ELISA positive. However, strains other than GII.4 and GI.3 were relatively uncommon in the clinical study, and literature supports GII.4 as the predominant strain in the US. Performance in the clinical study generally parallels that seen for archived specimens.

Other clinical supportive data (when a. and b. are not applicable): C.
Not applicable.

4. Clinical cut-off:

Not applicable.

5. Expected values/Reference range:

Noroviruses are a frequent cause of gastroenteritis outbreaks in semi-closed settings that involve children and/or adults such as day-care centers, nurseries. hospitals, nursing homes, prisons, and cruise ships, or other settings that may facilitate person-person spread. Noroviruses account for ~50% of all acute gastroenteritis outbreaks worldwide, although the proportion of outbreaks expected to be positive and the rate of positive test results within an outbreak depend on a number of factors, including (among others), the prevalence of

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norovirus within the population, the specific genotype(s) circulating, how rapidly specimens are taken, and the setting of the outbreak.

The expected value for RIDASCREEN® Norovirus 3rd Generation should be negative, although approximately 1/3 of infected patients may be asymptomatic. The design of the clinical study did not permit definitive analysis of the effects of age or gender on test performance, but exploratory analysis suggested that performance was similar across all age ranges and for both genders.

N. Proposed Labeling:

The labeling is sufficient and satisfies the requirements of 21 CFR Part 809.10.

O. Conclusion:

The petition for Evaluation of Automatic Class III Designation for this device is accepted. The device is classified as Class II under regulation 21 CFR 866.3395 with special controls. The special control guidance document "Class II Special Controls Guidance Document: Immunoassay or Antigen Detection-based In Vitro Diagnostic Devices for Norovirus Detection" will be available shortly.

Regulation Number and Section

§ 866.3395 Norovirus serological reagents.

(a)
Identification. Norovirus serological reagents are devices that consist of antigens and antisera used in serological tests to detect the presence of norovirus antigens in fecal samples. These devices aid in the diagnosis of norovirus infection in the setting of an individual patient with symptoms of acute gastroenteritis when the individual patient is epidemiologically linked to other patients with symptoms of acute gastroenteritis and/or aid in the identification of norovirus as the etiology of an outbreak of acute gastroenteritis in the setting of epidemiologically linked patients with symptoms of acute gastroenteritis.(b)
Classification. Class II (special controls). The device is exempt from the premarket notification procedures in subpart E of part 807 of this chapter subject to the limitations in § 866.9. The special control is FDA's guidance document entitled “Class II Special Controls Guidance Document: Norovirus Serological Reagents.” See § 866.1(e) for the availability of this guidance document.