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Unexpectedly High False-Positive Rates for Haemophilus influenzae Using a Meningoencephalitis Syndromic PCR Panel in
Marie-Céline Zanella1,2, Abdessalam Cherkaoui1, Vladimira Hinic3
1Laboratory of Bacteriology, Division of Laboratory Medicine and Division of Infectious Diseases, University of Geneva Hospitals, Geneva, Switzerland.
Abstract:
False-positive results in the diagnostic of meningitis and encephalitis pose important challenges. This study aimed to determine false-positive rates for Haemophilus influenzae in cerebrospinal fluids evaluated by the BioFire FilmArray® Meningitis/Encephalitis Panel. We conducted a retrospective study of all H. influenzae-positive FilmArray®. Meningitis/Encephalitis Panel results from June 2016 to October 2019 in two Swiss university hospitals. Cases were classified as true positive, likely true-positive, and likely false-positive results according to cerebrospinal fluid culture, H. influenzae-specific quantitative real-time PCR (qPCR), and Gram staining, as well as culture of other materials. We performed 3,082 panels corresponding to 2,895 patients: 0.6% of the samples (18/3,082) were positive for H. influenzae. Culture and H. influenzae-specific qPCR were performed on 17/18 (94.4%) and 3/18 (16.7%) cerebrospinal fluid samples, respectively; qPCR was negative in all cases. Among 17 samples sent for culture, 10 concerned patients were not treated with antibiotics prior to lumbar puncture. Only 1/17 revealed growth of H. influenzae and was classified as a true positive. We further classified 3/18 (16.7%) cases with the identification of Gram-negative rods in the cerebrospinal fluid or positive blood cultures for H. influenzae as likely true-positive and 14/18 (77.8%) cases as likely false-positive. Diagnostic results should always be interpreted together with the clinical presentation, cerebrospinal fluid analysis, and other available microbiological results. All H. influenzae-positive results should be viewed with special caution and a H. influenzae-specific qPCR should be systematically considered.
Insights
False-positive results for Haemophilus influenzae meningitis are common. A study found 77.8% of positive BioFire FilmArray results were likely false, emphasizing cautious interpretation and confirmatory testing.
Area of Science:
- Clinical Microbiology
- Infectious Diseases
- Molecular Diagnostics
Background:
- False-positive results in diagnosing meningitis and encephalitis present significant clinical challenges.
- Accurate identification of pathogens is crucial for appropriate patient management and treatment.
Purpose of the Study:
- To determine the false-positive rates of Haemophilus influenzae detection using the BioFire FilmArray Meningitis/Encephalitis Panel.
- To evaluate the reliability of the assay for H. influenzae in cerebrospinal fluid samples.
Main Methods:
- Retrospective analysis of H. influenzae-positive BioFire FilmArray results from June 2016 to October 2019.
- Classification of results using cerebrospinal fluid culture, H. influenzae-specific quantitative PCR (qPCR), and Gram staining.
- Comparison with other microbiological data, including blood cultures.
Main Results:
- Out of 3,082 panels, 18 (0.6%) were positive for H. influenzae.
- 14 out of 18 (77.8%) H. influenzae-positive results were classified as likely false-positive.
- Only one case was confirmed as true-positive by culture; qPCR was negative in all tested samples.
Conclusions:
- The BioFire FilmArray panel shows a high rate of likely false-positive results for H. influenzae.
- H. influenzae-positive results require careful interpretation alongside clinical presentation and other diagnostic tests.
- Consideration of H. influenzae-specific qPCR as a confirmatory method is recommended.
