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Evaluation of the Biofire FilmArray meningitis/encephalitis assay for the detection of Cryptococcus neoformans/gattii
T T Van1, T H Kim2, S M Butler-Wu2
1Department of Pathology, Harbor-UCLA Medical Center, Torrance, CA, USA; Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
Objectives:
Cryptococcal meningitis (CM) remains an important cause of morbidity and mortality among immunocompromised patients. Laboratory diagnostics for CM includes antigen detection, staining and culture. Data on the performance of the Biofire® FilmArray® meningitis/encephalitis (ME) panel for detecting Cryptococcus neoformans/gattii is limited, with several reports describing false negativity for this target.
Methods:
A retrospective analysis of 1384 physician-ordered ME panel tests ordered between January 2017 to October 2018 was performed. ME panel results were compared to cerebrospinal fluid (CSF) cryptococcal antigen (CrAg) and CSF culture testing and clinical significance of cryptococcal detection was determined.
Results:
There were 34 patients positive for cryptococcal detection by either ME panel, CSF CrAg or CSF culture in 2.7% of CSF specimens tested (38/1384). Of the 34 patients positive for cryptococcal detection, 85.3% were human immunodeficiency virus positive (29/34). The ME panel detected 32/38 (84.2%) cryptococcal-positive specimens, culture detected 28/38 (73.7%) and CSF CrAg was positive in 37/38 specimens (97.4%). The ME panel had a sensitivity and specificity of 96.4% (95% CI 81.7-99.9%) and 99.6% (95% CI 99.2-99.9%) compared with culture, and 83.8% (95% CI 68.0-93.8%) and 99.9% (95% CI 99.6-100.0%) compared to CSF CrAg testing, respectively. CrAg titres were lower among ME panel-negative, culture-negative specimens compared with ME panel-positive, culture-negative specimens (reciprocal median end-point titres of 128 ± 60 vs. 1920 ± 1730, p 0.04). All five CrAg-positive, ME panel- and culture-negative specimens were obtained from previously treated CM patients.
Discussion:
The ME panel had high correlation with CSF culture and a somewhat lower correlation with CSF CrAg testing. The potential utility of using negative ME panel test results to predict culture sterility among patients undergoing treatment for CM warrants further study.
Insights
The Biofire® FilmArray® meningitis/encephalitis (ME) panel shows high accuracy for detecting Cryptococcus in cerebrospinal fluid, correlating well with culture. However, its performance compared to cryptococcal antigen (CrAg) testing is lower, especially in treated patients.
Area of Science:
- Clinical Microbiology
- Infectious Diseases
- Molecular Diagnostics
Background:
- Cryptococcal meningitis (CM) is a significant cause of illness and death in immunocompromised individuals.
- Current diagnostic methods for CM include antigen detection, staining, and culture.
- Limited data exists on the Biofire® FilmArray® meningitis/encephalitis (ME) panel's performance for Cryptococcus detection, with some reports of false negatives.
Purpose of the Study:
- To evaluate the performance of the Biofire® FilmArray® (ME) panel for detecting Cryptococcus neoformans/gattii in cerebrospinal fluid (CSF).
- To compare ME panel results with CSF cryptococcal antigen (CrAg) and CSF culture.
- To assess the clinical significance of Cryptococcus detection using the ME panel.
Main Methods:
- Retrospective analysis of 1384 physician-ordered ME panel tests from January 2017 to October 2018.
- Comparison of ME panel results against CSF CrAg and CSF culture.
- Determination of the clinical significance of cryptococcal detection.
Main Results:
- Cryptococcus was detected in 2.7% (38/1384) of CSF specimens; 85.3% of positive cases were in HIV-positive patients.
- The ME panel detected 84.2% of positive specimens, compared to 73.7% for culture and 97.4% for CSF CrAg.
- ME panel sensitivity and specificity were 96.4% and 99.6% versus culture, and 83.8% and 99.9% versus CSF CrAg.
Conclusions:
- The ME panel demonstrates high correlation with CSF culture for Cryptococcus detection.
- Correlation between the ME panel and CSF CrAg testing was lower.
- Further research is needed to explore the utility of negative ME panel results in predicting culture sterility in treated CM patients.
