Abbott RealTime MTB PCR delivers high sensitivity and specificity on bronchoscopic specimens for pulmonary TB
The study reports an evaluation of the Abbott RealTime Mycobacterium tuberculosis PCR on 6,988 bronchoscopic specimens from 4,118 patients with suspected pulmonary TB in a low-prevalence setting. After resolving clinical discrepancies, investigators found the assay demonstrated a sensitivity of 83.9% and a specificity of 99.9%, surpassing the World Health Organization Target Product Profiles for molecular TB diagnostics. The moderate-complexity automated test is already integrated into WHO-recommended algorithms with reflex rifampicin and isoniazid resistance testing. These findings provide laboratory directors with validated performance data for using this NAAT when conventional sputum samples are insufficient or unavailable.
The original study
Clinical performance of the Abbott RealTime Mycobacterium tuberculosis (MTB) PCR on bronchoscopic specimens for diagnosing pulmonary tuberculosis.
- Authors
- Ripoll JJ, Clari MÁ, Orta N, Chouman R, Signes-Costa J, Franco J, et al.
- Journal
- European journal of clinical microbiology & infectious diseases : official publication of the European Society of Clinical Microbiology
- Type
- Journal Article
- PMID
- 42714826
Original abstract
PURPOSE: We evaluated the performance of the Abbott RealTime Mycobacterium tuberculosis (MTB) PCR (RT MTB) on bronchoscopic specimens using conventional culture as the reference standard in a low-Tuberculosis (TB) prevalence setting. METHODS: A total of 6,988 specimens (4,682 bronchial aspirates [BAS] and 2,306 bronchoalveolar lavages [BAL]) from 4,118 patients with suspected pulmonary TB were included. When BAS and BAL specimens from the same bronchoscopy procedure were available, these were mixed 1:1 prior to culture inoculation and PCR testing. Following processing, specimens were inoculated into a Löwenstein-Jensen and a Bactec MGIT 960 tube and incubated at 37 °C for 3 months and at 35 °C for 8 weeks, respectively. RT MTB was performed as indicated by the manufacturer. RT MTB targets the insertion sequence IS6110 and the protein antigen B (PAB) gene, both highly conserved within the Mycobacterium tuberculosis complex. Whole genome Next generation sequencing of clinical MTBC isolates was performed when indicated. RESULTS: Among the 104 culture-positive specimens, 84 (1.2%) were detected by PCR. Additionally, 16 specimens (0.3% of all samples), from 16 patients, were PCR-positive despite negative culture results. Conversely, 20 specimens (0.4% of all samples), from 19 patients, were culture-positive but not detected by PCR. No significant differences were found between PCR-positive and PCR-negative specimens with respect to the number of IS6110 copies per isolate or PAB gene sequences (P = 0.69). Finally, there were 4,683 specimens (97.4%) from the remaining 4,014 patients tested PCR-negative/Culture-negative. Following the resolution of discrepancies based on clinical grounds the sensitivity and specificity of RT MTB were 83.9% (CI 95%, 76.0-90.0) and 99.9% (CI 95%, 99.9-99.9), respectively. These results exceed the minimum performance requirements defined in the WHO Target Product Profiles for molecular TB diagnostics. Although RT MTB is not a point-of-care test but rather a moderate-complexity automated NAAT, it is recommended by WHO as part of the Abbott RealTime MTB/MTB RIF-INH testing algorithm, in which MTBC detection by RT MTB is followed by reflex testing with the MTB RIF/INH assay for detection of rifampicin and isoniazid resistance. CONCLUSION: RT MTB shows a good performance on bronchoscopic specimens.