(299 days)
The BBL® MGIT™ Mycobacteria Growth Indicator Tube and BBL® MGIT™ supplemented with BBL® MGIT™ OADC and BBL® MGIT™ supplemented with BBL® MGIT™ PANTA antibiotic mixture, is intended for the detection and recovery of mycobacteria from decontaminated clinical specimens (except urine) and sterile body fluids (except blood). Acceptable clinical specimen types are digested and decontaminated.
The BBL® MGIT™ Mycobacteria Growth Indicator Tube contains 4 mL of modified Middlebrook 7H9 Broth Base. The complete medium is supplemented with 0.5 mL OADC enrichment and 0.1 mL of PANTA antibiotic mixture, when necessary. The medium components are substances essential for the growth of mycobacteria. A fluorescent compound is embedded in the bottom of the BBL® MGIT™ tube which is sensitive to the presence of oxygen dissolved in the broth. Specimens are inoculated (0.5 mL) into the BBL® MGIT™ tube and incubated at the appropriate temperature. Tubes are read daily from the second day of inoculation. Actively respiring microorganisms consume the oxygen and allow the compound to fluoresce. Each inoculated BBL® MGIT™ tube is compared to the fluorescence Positive Control and Negative Control tube to assist in the interpretation of a positive signal from the BBL® MGIT™ tube. A BBL® MGIT™ tube which exhibits fluorescence comparable to the Positive Control tube is considered presumptively positive for growth.
The provided text describes the BBL® MGIT™ Mycobacteria Growth Indicator Tube, intended for the detection and recovery of mycobacteria from clinical specimens. The device relies on an oxygen-sensitive fluorescent sensor that detects oxygen consumption by actively respiring microorganisms.
Here's an analysis of the acceptance criteria and the study that proves the device meets them:
1. A table of acceptance criteria and the reported device performance
The document does not explicitly state pre-defined acceptance criteria in terms of numerical thresholds for sensitivity, specificity, or false positive rates. However, the study aims to show comparable performance to predicate devices. Therefore, the "acceptance criteria" appear to be implicit: the BBL® MGIT™ tubes should perform similarly to or better than the BACTEC® 460TB System and the BBL® SEPTI-CHEK® AFB Mycobacteria Culture System in terms of recovery rate and time to detection, while maintaining an acceptable false positive rate.
| Metric | Acceptance Criteria (Implicit: Comparable to Predicate) | Reported BBL® MGIT™ Performance |
|---|---|---|
| Mycobacterial Recovery Rate | Comparable to BACTEC® 460TB System (79%) and BBL® SEPTI-CHEK® AFB (79%) | 77% (253 of 330 isolates) |
| False Positive Rate | Acceptably low (no explicit numerical criterion, but likely aiming for minimal |
false positives relative to clinical impact) | 0.5% |
| Time-to-Detection | Comparable to predicate devices (not explicitly stated, but implies being efficient | 14.1 days (average for all mycobacteria) |
| Unrecovered Isolates | Minimally higher than predicate devices (with further recovery via recommended second medium) | 3.7% (isolates recovered by reference, but not MGIT) |
| Breakthrough Contamination Rate | Acceptably low | 9.7% |
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 for Test Set: A combined total of 2801 clinical specimens were evaluated.
- Data Provenance:
- Country of origin: Not explicitly mentioned, but the submitting company is Becton Dickinson Microbiology Systems, located in Sparks, MD, USA. It's highly probable the studies were conducted in the USA.
- Retrospective or Prospective: Not explicitly stated. However, external evaluations are typically conducted prospectively to compare a new device against existing methods in real-world clinical settings. The description of "specimens were evaluated" and "isolates recovered during the study" suggests a prospective collection and testing over a period.
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 document does not specify the number of experts or their qualifications for establishing the ground truth. The ground truth was established by culture results from reference methods:
- BACTEC® 460TB System
- BBL® SEPTI-CHEK® AFB Mycobacteria Culture System
- Conventional solid agar media
Presumably, trained laboratory personnel followed standard protocols for these reference systems to determine the presence or absence of mycobacteria and to identify isolates.
4. Adjudication method (e.g. 2+1, 3+1, none) for the test set
The document does not describe an adjudication method involving human experts. The ground truth for mycobacterial presence was determined directly by the growth observed in the reference culture systems. If there was discordance between the BBL® MGIT™ and the reference, it was noted as an unrecovered isolate by the MGIT, not subjected to a separate expert adjudication process to determine a "true" positive or negative outside of the reference method's result.
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: No, this was not a multi-reader, multi-case (MRMC) comparative effectiveness study.
- AI (Artificial Intelligence): The BBL® MGIT™ device is a culture-based diagnostic system, not an AI-assisted diagnostic tool. Therefore, there's no discussion of AI assistance or its effect size on human readers. The growth detection is described as "Manual observation of fluorescence via excitation with longwave UV light."
6. If a standalone (i.e. algorithm only without human-in-the loop performance) was done
The BBL® MGIT™ device itself is a standalone diagnostic tool in the sense that its detection mechanism (fluorescence) is independent of human interpretation for the initial signal. However, the final interpretation of a "presumptively positive" signal and subsequent identification of the mycobacteria would involve human intervention. The "manual observation of fluorescence" indicates human involvement in reading the fluorescence.
7. The type of ground truth used (expert consensus, pathology, outcomes data, etc.)
The ground truth used was culture-based detection and recovery of mycobacteria using established reference methods:
- BACTEC® 460TB System
- BBL® SEPTI-CHEK® AFB Mycobacteria Culture System
- Conventional solid agar media
The presence of mycobacteria, and their specific isolates, as determined by growth in one or more of these reference systems, formed the ground truth against which the BBL® MGIT™ performance was compared.
8. The sample size for the training set
The document does not specify a separate "training set" in the context of machine learning or AI models. This device is a culture medium system, not a software algorithm that requires training data in that sense. The "internal testing" mentioned likely involved R&D and optimization of the medium components and detection method, rather than training a predictive model.
9. How the ground truth for the training set was established
As there was no explicit "training set" for an algorithm, the concept of establishing ground truth for it doesn't apply directly in this context. The "internal testing" would have relied on known mycobacterial strains and clinical samples where the presence/absence of mycobacteria was confirmed by standard laboratory methods.
§ 866.2560 Microbial growth monitor.
(a)
Identification. A microbial growth monitor is a device intended for medical purposes that measures the concentration of bacteria suspended in a liquid medium by measuring changes in light scattering properties, optical density, electrical impedance, or by making direct bacterial counts. The device aids in the diagnosis of disease caused by pathogenic microorganisms.(b)
Classification. Class I. With the exception of automated blood culturing system devices that are used in testing for bacteria, fungi, and other microorganisms in blood and other normally sterile body fluids, this device is exempt from the premarket notification procedures in subpart E of part 807 of this chapter.