BD PROBETEC ET LEGIONELLA PNEUMOPHILA (LP) AMPLIFIED DNA ASSAY

K033861 · Becton, Dickinson & CO · LQH · Mar 9, 2004 · Microbiology

Device Facts

• Record ID: K033861
• Device Name: BD PROBETEC ET LEGIONELLA PNEUMOPHILA (LP) AMPLIFIED DNA ASSAY
• Applicant: Becton, Dickinson & CO
• Product Code: LQH · Microbiology
• Decision Date: Mar 9, 2004
• Decision: SESE
• Submission Type: Traditional
• Regulation: 21 CFR 866.3300
• Device Class: Class 2

Indications for Use

The BD ProbeTec™ ET Legionella pneumophila (LP) Amplified DNA Assay, for use with the BD ProbeTec™ ET System, employs Strand Displacement Amplification (SDA) technology for the direct qualitative detection of L.pneumophila DNA (serogroups 1-14) in sputum from patients with a clinical suspicion of pneumonia. It is intended to aid in the presumptive diagnosis of Legionnaires' disease in conjunction with culture and other methods.

Device Story

The BD ProbeTec™ ET LP Amplified DNA Assay is an in vitro diagnostic test used with the BD ProbeTec™ ET System. It processes sputum specimens from patients suspected of having pneumonia. The device utilizes Strand Displacement Amplification (SDA) technology to amplify and detect target L. pneumophila DNA sequences. Reagents are contained in disposable microwells; the system uses DNA polymerase and restriction endonuclease for amplification. An Internal Amplification Control (IAC) is co-amplified to monitor for specimen inhibitors. A thermally controlled fluorescent reader monitors the reaction in real-time. The system calculates PAT (Passes After Threshold) scores to determine the presence or absence of target DNA. Results are automatically reported as positive, negative, or indeterminate. The assay is intended for use by laboratory professionals to aid clinicians in the presumptive diagnosis of Legionnaires' disease alongside culture and other diagnostic methods.

Clinical Evidence

Prospective study (n=114) and retrospective study (n=83) evaluated performance against culture. Prospective study showed 100% specificity (114/114). Retrospective study showed 91.3% positive agreement (21/23) and 86.7% negative agreement (52/60) with culture.

Technological Characteristics

Strand displacement amplification (SDA) technology; uses DNA polymerase and restriction endonuclease. Targets 84 bp region of mip gene. Includes internal amplification control (IAC). Form factor: disposable microwells for use with BD ProbeTec ET System. Thermally controlled fluorescent reader for detection.

Indications for Use

Indicated for qualitative detection of L. pneumophila DNA (serogroups 1-14) in sputum specimens from patients with clinical suspicion of pneumonia to aid in presumptive diagnosis of Legionnaires' disease. For prescription use.

Regulatory Classification

Identification

Haemophilus spp. serological reagents are devices that consist of antigens and antisera, including antisera conjugated with a fluorescent dye, that are used in serological tests to identify Haemophilus spp. directly from clinical specimens or tissue culture isolates derived from clinical specimens. The identification aids in the diagnosis of diseases caused by bacteria belonging to the genus Haemophilus and provides epidemiological information on diseases cause by these microorganisms. Diseases most often caused by Haemophilus spp. include pneumonia, pharyngitis, sinusitis, vaginitis, chancroid venereal disease, and a contagious form of conjunctivitis (inflammation of eyelid membranes).

Special Controls

*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 § 866.9.

Predicate Devices

• Binax NOW™ Legionella Urinary Test (k934965)

Submission Summary (Full Text)

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510(k) SUBSTANTIAL EQUIVALENCE DETERMINATION
DECISION SUMMARY

A. 510(k) Number:
k033861

B. Analyte:
Legionella pneumophila DNA

C. Type of Test:
DNA amplification test

D. Applicant:
Becton, Dickinson and Company

E. Proprietary and Established Names:
BD ProbeTec™ ET Legionella pneumophila (LP) Amplified DNA Assay

F. Regulatory Information:
1. Regulation section:
21 CFR 866.3300; Haemophilus spp. Serological Reagents
2. Classification:
Class II
3. Product Code:
LQH; DNA-reagents, Legionella
4. Panel:
Microbiology (83)

G. Intended Use:
1. Intended use(s):
The BD ProbeTec™ ET Legionella pneumophila (LP) Amplified DNA Assay, for use with the BD ProbeTec ET System, employs Strand Displacement Amplification (SDA) technology for the direct qualitative detection of Legionella pneumophila DNA (serogroups 1-14) in sputum specimens from patients with a clinical suspicion of pneumonia. It is intended to aid in the presumptive diagnosis of Legionnaires' disease in conjunction with culture and other methods.
2. Indication(s) for use:
The BD ProbeTec™ ET Legionella pneumophila (LP) Amplified DNA Assay, for use with the BD ProbeTec ET System, employs Strand Displacement Amplification (SDA) technology for the direct qualitative detection of Legionella pneumophila DNA (serogroups 1-14) in sputum specimens from patients with a clinical suspicion of pneumonia. It is intended

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to aid in the presumptive diagnosis of Legionnaires' disease in conjunction with culture and other methods.

3. Special condition for use statement(s): Not applicable
4. Special instrument Requirements: BD ProbeTec™ System

## H. Device Description:

The Assay is based on the simultaneous amplification and detection of target DNA sequences using nucleic acid primers and fluorescently-labeled detector probes in a process known as strand displacement amplification (SDA). The SDA reagents are dried in two separate disposable microwells. Processed sample containing DNA is added to a Priming Microwell, which contains the amplification primers, fluorescently-labeled detector probes, and other reagents necessary for amplification. The primers amplify an 84 base pair region of the *L. pneumophila* macrophage infectivity potentiator (mip) gene that is conserved across all serogroups of the species. Following incubation, the reaction mixture is transferred to an Amplification Microwell, which contains two enzymes (a DNA polymerase and a restriction endonuclease) necessary for SDA. The Amplification Microwells are sealed to prevent contamination and then incubated in a thermally controlled fluorescent reader, which monitors each reaction for the generation of amplified products. Each reaction co-amplifies and detects an Internal Amplification Control (IAC), as well as the target DNA. The purpose of the IAC is to verify that proper conditions exist for amplification and to reduce the possibility of reporting a false negative result due to specimen inhibitors. The presence or absence of *L. pneumophila* DNA is determined by calculating PAT scores (Passes After Threshold) for the specimen based on predefined threshold values. The instrument automatically reports the results as positive, negative or indeterminate.

## I. Substantial Equivalence Information:

1. Predicate device name(s): Binax NOW™ Legionella Urinary Test
2. Predicate K number(s): k934965
3. Comparison with predicate:

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| Similarities | | |
| --- | --- | --- |
| Item | Device | Predicate |
| Procedure | Qualitative; detection of Legionella pneumophila | Qualitative; detection of Legionella pneumophila |
| Differences | | |
| Item | Device | Predicate |
| Assay | Nucleic acid amplification and probe detection | Enzyme Immunoassay (EIA), membrane assay |
| Specimen Type | Sputum | Urine |

J. Standard/Guidance Document Referenced (if applicable):
Not applicable

K. Test Principle:
Strand displacement amplification (SDA)

L. Performance Characteristics (if/when applicable):
1. Analytical performance:
a. Precision/Reproducibility:
Reproducibility of the BD ProbeTec™ ET LP Assay was assessed at three laboratories by testing a panel consisting of 24 samples seeded in PBS/BSA. The panel comprised 12 samples that were negative for L. pneumophila; three low (300 CFU/reaction) and three high (500 CFU/reaction) positive samples of L. pneumophila; and three low (30 Elementary Bodies (EB)/reaction, 300 CFU/reaction, 900 cells/reaction, respectively) and three high (50 EB/reaction, 500 CFU/reaction, 1500 cells/ reaction, respectively) positive samples each containing Chlamydophila pneumoniae (CP), L. pneumophila, and Mycoplasma pneumoniae (MP). The %CV varied from 2 to 6%.
b. Linearity/assay reportable range:
Not applicable
c. Traceability (controls, calibrators, or method):
Not applicable
d. Detection limit:
The analytical sensitivity of the BD ProbeTec™ ET LP Assay across 14 different serogroups of L. pneumophila was determined by diluting bacterial suspensions to levels of 0, 150, 300 and 450 Colony Forming Units (CFU) per reaction. Based on 100% positivity, the analytical sensitivity for serogroups 2-10 and 12 was 150 CFU/reaction. The analytical sensitivity for serogroups 1 and 11

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was 300 CFU/reaction; serogroup 13 was 450 CFU/reaction; and serogroup 14 was 700 CFU/reaction.

The analytical sensitivity of the BD ProbeTec™ ET LP Assay in the presence of a lower respiratory specimen matrix was determined by seeding a macrophage-infected stock of *L. pneumophila* serogroup 1 into sputum at levels of 0, 150, 300 and 450 CFU per reaction. The specimens were processed according to the lower respiratory processing procedure and assayed in triplicate. Based on 100% positivity, the analytical sensitivity for lower respiratory specimens was 150 CFU/reaction.

e. Analytical specificity:

A total of 79 microorganisms (69 bacteria, one yeast and nine viruses) were evaluated using the BD ProbeTec™ ET LP Assay. Bacterial isolates were tested at concentrations ranging from 1 x 10⁶ CFU/mL to 1 x 10⁸ CFU/mL. Viruses were tested at a concentration of 1 x 10⁶ viral particles/mL. None of the microorganisms tested produced a positive result or inhibited the Internal Amplification Control (IAC).

f. Assay cut-off:

The threshold values for both the *L. pneumophila* target DNA and the IAC were initially established using Receiver Operator Characteristic curve analyses of data obtained from positive and negative controls. These threshold values were verified in clinical studies and with retrospective *L. pneumophila* positive and negative specimens.

2. Comparison studies:

a. Method comparison with predicate device:

Study 1: The BD ProbeTec™ ET LP Assay was evaluated prospectively at seven clinical centers within the United States and Canada during the 2002–2003 respiratory season. A sputum specimen and a urine specimen were collected from each patient. Sputum specimens were tested using the BD ProbeTec™ ET LP Assay, *Legionella* culture, and a Direct Fluorescent Antibody assay (DFA). Urine specimens were tested using a commercially available *L. pneumophila* urinary antigen assay.

A total of 114 sputum specimens collected from 114 patients met the criteria for inclusion in the study (i.e., radiographic evidence of pneumonia, patients ≥ 13 years of age, on antibiotics ≤ 14 days, valid specimen types collected, appropriate reference methods conducted, etc.). Results of the sputum specimens were compared to the culture result to estimate performance characteristics. There were no positive specimens found by culture or Probe Tec™ ET LP Assay. The specificity was 100% (114/114).

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Study 2: The BD ProbeTec™ ET LP Assay was also evaluated with 83 retrospective sputum specimens acquired from clinical sites within the United States, Europe, and Canada. Each site tested the sputum specimens in the BD ProbeTec™ ET LP Assay and compared the results to the culture result. The positive agreement was 91.3% (21/23), the negative agreement was 86.7% (52/60) and the overall agreement was 88% (73/83).

b. Matrix comparison: Not applicable

3. Clinical studies:
a. Clinical sensitivity: Not applicable
b. Clinical specificity: Not applicable
c. Other clinical supportive data (when a and b are not applicable): Not applicable

4. Clinical cut-off: Not applicable
5. Expected values/Reference range: Not applicable

M. Conclusion:
The Performance characteristics reported here for the device indicates that it is comparable to other such test kits currently in the market.