RIFAMPICIN ANTIMICROBIAL SUSCEPTIBILITY TEST DISC by OXOID, LTD.

Antimicrobial Susceptibility Test Discs are indicated for the semi-quantitative susceptibility testing by agar diffusion test procedure of rapidly growing micro-organisms. These include : Staphylococcus spp., and modified by procedures, Haemophilus influenzae.

Device Description

Oxoid Rifampicin Susceptibility Test Disc

AI/ML Overview

This document is an FDA 510(k) clearance letter for an in vitro diagnostic device (IVD), specifically an antimicrobial susceptibility test disc. IVDs, especially those cleared under a 510(k), are often evaluated based on their performance characteristics compared to a predicate device, rather than a full clinical study with acceptance criteria like a drug or a novel medical device. The document itself does not contain the detailed study results or acceptance criteria.

However, based on the nature of antimicrobial susceptibility testing and the typical requirements for such devices, I can infer and generally describe the likely acceptance criteria and type of study. I will fill in the table and information, making educated assumptions where the specific details are not provided in the given text.

I must emphasize that the provided text does not include the detailed study results or acceptance criteria directly. This information would typically be in the 510(k) submission itself, which this document is a response to.

1. Table of Acceptance Criteria and Reported Device Performance

For an antimicrobial susceptibility test disc, the primary performance metrics are related to its ability to accurately classify bacterial isolates as susceptible, intermediate, or resistant to a given antibiotic (Rifampicin in this case). The acceptance criteria are typically established in comparison to a reference method (e.g., broth microdilution or agar dilution as described by CLSI/NCCLS standards).

Acceptance Criteria (Inferred)	Reported Device Performance (Inferred/Typical for 510k IVD)
Essential Agreement (EA): Percentage of isolates where the disc diffusion category (S, I, R) matches the reference method category.	Typically >90% (often 95-99%) for each drug-bug combination. For the Oxoid Rifampicin disc, it would need to demonstrate high essential agreement across relevant Staphylococcus spp. and Haemophilus influenzae. The exact reported percentage is not in this document.
Category Agreement (CA): Percentage of isolates where the disc diffusion category (S, I, R) exactly matches the reference method category (similar to EA but sometimes used to denote a stricter match).	Typically >90% (often 95-99%). The exact reported percentage is not in this document.
Minor Discrepancies: Percentage of isolates with a one-off category difference (e.g., reference is Susceptible, disc is Intermediate).	Typically <5-10% (often <5%). The exact reported percentage is not in this document.
Major Discrepancies (False Susceptible): Percentage of isolates where the disc diffusion indicates Susceptible, but the reference method indicates Resistant.	Typically <1.5-3.0%. These are clinically critical errors and must be very low. The exact reported percentage is not in this document.
Very Major Discrepancies (False Resistant): Percentage of isolates where the disc diffusion indicates Resistant, but the reference method indicates Susceptible.	Typically <1.5-3.0%. These are also clinically critical errors. The exact reported percentage is not in this document.
Zone Diameter Reproducibility: Consistent zone diameters when tested repeatedly under controlled conditions.	Standard deviation or coefficient of variation for zone diameters within acceptable limits (e.g., within 1-2 mm for 95% of replicates). The exact reported percentage or values are not in this document.
Growth/Inhibition Characteristics: Clear zones of inhibition for susceptible organisms, and clear growth for resistant organisms.	Qualitative observation of distinct growth patterns. The document mentions "semi-quantitative susceptibility testing by agar diffusion test procedure." The exact reported qualitative assessment is not in this document.
Quality Control Ranges: Zone diameters for specified QC organisms fall within established ranges.	The document mentions "The technical product insert details the Quality Control organisms to be use with this disc." This implies that the device demonstrated performance within established QC ranges for those organisms. The specific ranges and results are not in this document.

2. Sample size used for the test set and the data provenance

Sample Size for Test Set: The document does not specify the exact sample size. However, for a 510(k) submission for an antimicrobial susceptibility test, the test set would typically involve a statistically significant number of clinical isolates (e.g., hundreds, sometimes thousands) representing the target organisms (Staphylococcus spp., Haemophilus influenzae) and covering a range of resistance mechanisms to Rifampicin. This would often include a good representation of susceptible, intermediate, and resistant strains.
Data Provenance: The document does not explicitly state the country of origin or whether the data was retrospective or prospective. However, given Oxoid Limited is based in England, it is plausible that some or all of the clinical isolates used in the studies originated from European collections or clinical sites. Studies for 510(k) usually involve a combination of well-characterized reference strains and fresh clinical isolates, often collected prospectively or from well-maintained biobanks (making them retrospective by nature of collection but prospectively tested for the device).

3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts

Number of Experts & Qualifications: For antimicrobial susceptibility testing, the "ground truth" is typically established by performing a reference method (e.g., CLSI/NCCLS broth microdilution or agar dilution). This is a standardized laboratory procedure, not typically an expert consensus reading of images or clinical cases. The interpretation of the reference method results and the categorization into S/I/R is based on established clinical breakpoints published by organizations like CLSI. Therefore, "experts" in the sense of adjudicators are not usually involved in establishing the ground truth directly, beyond ensuring the reference method is performed and interpreted correctly by qualified microbiologists or laboratory scientists.

4. Adjudication method for the test set

Adjudication Method: Not applicable in the traditional sense. As explained above, the "ground truth" is determined by a standardized reference method. Any discrepancies between the investigational device and the reference method would be analyzed, but typically not "adjudicated" by multiple human readers in the way diagnostic imaging or pathology might be. If there were significant discrepancies, the reference method result would stand, and the investigational device's performance would be evaluated against that.

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

MRMC Study: Not applicable. This device is an in vitro diagnostic for antimicrobial susceptibility, not a device that involves human readers interpreting cases (like imaging devices aided by AI). Therefore, no MRMC study, AI assistance, or effect size related to human reader improvement would be relevant or performed for this type of product.

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

Standalone Performance: Partially applicable. The device itself is a disc that produces a zone of inhibition. The reading of this zone diameter and its interpretation into S/I/R categories can be done manually by a human or potentially by an automated zone reader (which might involve an algorithm). The primary performance evaluation would be for the accuracy of the zone diameter measurement and its correlation with the reference method, regardless of how the zone is read. This document pertains to the disc itself, not an automated reader. Therefore, the "standalone" performance would be how accurately the disc produces a zone that, when correctly measured and interpreted, correlates with the reference method.

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

Type of Ground Truth: The ground truth would be established by a standardized microbiological reference method, specifically a quantitative method like broth microdilution or agar dilution, interpreted according to established clinical breakpoints (e.g., CLSI/NCCLS guidelines). This is considered the gold standard for antimicrobial susceptibility testing.

8. The sample size for the training set

Sample Size for Training Set: The document does not provide information about a "training set." For an IVD like this, there isn't typically a "training set" in the machine learning sense. The device is a physical disc; its design (e.g., antibiotic concentration) is based on established microbiological principles and validated through performance studies. While developers might conduct initial studies to optimize disc concentration, this isn't usually termed a "training set" in regulatory submissions. The primary focus is on the performance evaluation (test set) against a gold standard.

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

Ground Truth for Training Set: Not applicable. As explained above, a "training set" as understood in AI/ML is not a concept typically applied to the development and validation of a simple physical IVD like an antimicrobial susceptibility disc. The ground truth for performance evaluation (the test set) is established using reference microbiological methods.

Summary

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Image /page/0/Picture/1 description: The image shows the logo for the U.S. Department of Health & Human Services. The logo consists of a circular seal with the text "DEPARTMENT OF HEALTH & HUMAN SERVICES - USA" arranged around the perimeter. Inside the circle is a stylized design featuring three abstract human figures or profiles facing to the right, with flowing lines above them.

Food and Drug Administration 2098 Gaither Road Rockville MD 20850

JAN 28 1998

Andy Hollingsworth Quality Systems Manager Oxoid Limited Wade Road Basingstoke Hants RG24 8PW England

Re: K971636

Trade Name: Oxoid Refampicin Antimicrobial Susceptibility Test Disc Regulatory Class: II Product Code: JTN Dated: November 17, 1997 Received: November 20, 1997

Dear Mr. Hollingsworth:

We have reviewed your Section 510(k) notification of intent to market the device referenced above and we have determined the device is substantially equivalent (for the indications for use stated in the enclosure) to devices marketed in interstate commerce prior to May 28, 1976, the enactment date of the Medical Device Amendments or to devices that have been reclassified in accordance with the provisions of the Federal Food, Drug, and Cosmetic Act (Act). You may, therefore, market the device, subject to the general controls provisions of the Act. The general controls provisions of the Act include requirements for annual registration, listing of devices, good manufacturing practice, labeling, and prohibitions against misbranding and adulteration.

If your device is classified (see above) into either class II (Special Controls) or class III (Premarket Approval), it may be subject to such additional controls. Existing major regulations affecting your device can be found in the Code of Federal Regulations. Title 21, Parts 800 to 895. A substantially equivalent determination assumes compliance with the current Good Manufacturing Practice requirement, as set forth in the Quality System Regulation (QS) for Medical Devices: General regulation (21 CFR Part 820) and that, through periodic (QS) inspections, the Food and Drug Administration (FDA) will verify such assumptions. Failure to comply with the GMP regulation may result in regulatory action. In addition, FDA may publish further announcements concerning your device in the Federal Register. Please note: this response to your premarket notification submission does not affect any obligation you might have under sections 531 through 542 of the Act for devices under the Electronic Product Radiation Control provisions, or other Federal Laws or Regulations.

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Under the Clinical Laboratory Improvement Amendments of 1988 (CLIA-88), this device may require a CLIA complexity categorization. To determine if it does, you should contact the Centers for Disease Control and Prevention (CDC) at (770)488-7655.

This letter will allow you to begin marketing your device as described in your 510(k) premarket notification. The FDA finding of substantial equivalence of your device to a legally marketed predicate device results in a classification for your device and thus, permits your device to proceed to the market.

If you desire specific advice for your device on our labeling regulation (21 CFR Part 801 and additionally 809.10 for in vitro diagnostic devices), please contact the Office of Compliance at (301) 594-4588. Additionally, for questions on the promotion and advertising of your device, please contact the Office of Compliance at (301) 594-4639. Also, please note the regulation entitled, "Misbranding by reference to premarket notification" (21 CFR 807.97). Other general information on your responsibilities under the Act may be obtained from the Division of Small Manufacturers Assistance at its toll free number (800) 638-2041 or at (301) 443-6597 or at its internet address "http://www.fda.gov/cdrh/dsmamain.html"

Sincerely yours,

Steven Gutman

Steven I. Gutman, M.D., M.B.A. Director Division of Clinical Laboratory Devices Office of Device Evaluation Center for Devices and Radiological Health

Enclosure

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510(K) Submission for Oxoid Antimicrobial Susceptibility Test Disc

RIFAMPIN

OXOID LTD

510(K) Number : K971636

Oxoid Rifampicin Susceptibility Test Disc Device Name :

Indication for Use :

The technical product insert details the Quality Control organisms to be use with this disc.

Rahme Alurichy for John Ticchiust
(Division Sign-Off)
Division of Clinical Laboratory Devices
John Ticchiust MD.
Interim Slick Micinist CBR

510(k) Number __ 1 - 9 -

lin McMurrer mis.
Interim Chief, Midwest
1/26/98

Prescription Use (Per 21 CFR 801.109)

Over-The Counter Use

(Optional Format 1-2-96)

Regulation Number and Section

§ 866.1620 Antimicrobial susceptibility test disc.

(a)
Identification. An antimicrobial susceptibility test disc is a device that consists of antimicrobic-impregnated paper discs used to measure by a disc-agar diffusion technique or a disc-broth elution technique the in vitro susceptibility of most clinically important bacterial pathogens to antimicrobial agents. In the disc-agar diffusion technique, bacterial susceptibility is ascertained by directly measuring the magnitude of a zone of bacterial inhibition around the disc on an agar surface. The disc-broth elution technique is associated with an automated rapid susceptibility test system and employs a fluid medium in which susceptibility is ascertained by photometrically measuring changes in bacterial growth resulting when antimicrobial material is eluted from the disc into the fluid medium. Test results are used to determine the antimicrobial agent of choice in the treatment of bacterial diseases.(b)
Classification. Class II (performance standards).