Diagnostic utility of auramine O smear microscopy for detecting non-tuberculous mycobacteria versus Mycobacterium tuberculosis complex in adult clinical samples: a 5-year retrospective study (2018–2022)
Abstract Background Fluorochrome smear microscopy is the method recommended for the direct examination of clinical samples for mycobacteria. However, no studies to date have comprehensively assessed the diagnostic utility of this method using auramine O stain for detecting non-tuberculous mycobacter...
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2025-07-01
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| author | Nadia Atiya Leong Tung Ong Thian Chee Loh Chee Kuan Wong Azwani Abdullah |
| author_facet | Nadia Atiya Leong Tung Ong Thian Chee Loh Chee Kuan Wong Azwani Abdullah |
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| description | Abstract Background Fluorochrome smear microscopy is the method recommended for the direct examination of clinical samples for mycobacteria. However, no studies to date have comprehensively assessed the diagnostic utility of this method using auramine O stain for detecting non-tuberculous mycobacteria (NTM) versus Mycobacterium tuberculosis complex (MTBC) in adult samples. Hence, this study aimed to investigate the diagnostic utility of auramine O smear microscopy (AOSM) for detecting NTM versus MTBC in adult samples, using mycobacterial culture as the reference standard. Methods This was a 5-year retrospective study conducted in a tertiary academic medical centre in Malaysia. Adult samples tested with both AOSM and mycobacterial culture from 1 January 2018 to 31 December 2022 were included in the analysis. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) with 95% confidence intervals (CI) were calculated using Open Epi Version 3.01. Results Of 12 016 adult samples that underwent both AOSM and mycobacterial culture, 19.0% (n = 2 288) were culture positive. NTM and MTBC accounted for 50.2% (n = 1 149) and 49.8% (n = 1 139) of the mycobacterial isolates, respectively. The diagnostic utility of AOSM for detecting NTM versus MTBC was 2.4% (95% CI 1.6%-3.5%) versus 53.6% (95% CI 50.6%-56.5%) for sensitivity, 93.8% (95% CI 93.3%-94.2%) versus 99.1% (95% CI 98.9%-99.3%) for specificity, 4.0% (95% CI 2.8%-5.8%) versus 86.4% (95% CI 83.8%-88.7%) for PPV and 90.1% (95% CI 90.0%-90.2%) versus 95.3% (95% CI 95.0%-95.6%) for NPV. Conclusions The diagnostic utility of AOSM was limited by poor sensitivity and PPV for NTM, and by poor sensitivity for MTBC. A positive AOSM result was a much more reliable indicator of the presence of MTBC than of NTM. In settings with a higher burden of TB than NTM disease, AOSM-positive patients with a clinical history suggestive of TB disease should be considered for TB treatment initiation while awaiting culture confirmation. In contrast, AOSM-positive patients whose clinical history is not strongly suggestive of TB—or is suggestive of NTM disease—should undergo additional testing using alternative methods, such as rapid molecular assays, that can reliably detect and distinguish between MTBC and NTM while awaiting culture confirmation. |
| format | Article |
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| institution | Kabale University |
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| spelling | doaj-art-23a58aec4e814d6e9fb9713b09357f6d2025-08-20T04:01:52ZengBMCBMC Infectious Diseases1471-23342025-07-012511810.1186/s12879-025-11298-3Diagnostic utility of auramine O smear microscopy for detecting non-tuberculous mycobacteria versus Mycobacterium tuberculosis complex in adult clinical samples: a 5-year retrospective study (2018–2022)Nadia Atiya0Leong Tung Ong1Thian Chee Loh2Chee Kuan Wong3Azwani Abdullah4Department of Medical Microbiology, Faculty of Medicine, Universiti MalayaDepartment of Medical Microbiology, Faculty of Medicine, Universiti MalayaDivision of Respiratory Medicine, Department of Medicine, Faculty of Medicine, Universiti MalayaDivision of Respiratory Medicine, Department of Medicine, Faculty of Medicine, Universiti MalayaDepartment of Medical Microbiology, Faculty of Medicine, Universiti MalayaAbstract Background Fluorochrome smear microscopy is the method recommended for the direct examination of clinical samples for mycobacteria. However, no studies to date have comprehensively assessed the diagnostic utility of this method using auramine O stain for detecting non-tuberculous mycobacteria (NTM) versus Mycobacterium tuberculosis complex (MTBC) in adult samples. Hence, this study aimed to investigate the diagnostic utility of auramine O smear microscopy (AOSM) for detecting NTM versus MTBC in adult samples, using mycobacterial culture as the reference standard. Methods This was a 5-year retrospective study conducted in a tertiary academic medical centre in Malaysia. Adult samples tested with both AOSM and mycobacterial culture from 1 January 2018 to 31 December 2022 were included in the analysis. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) with 95% confidence intervals (CI) were calculated using Open Epi Version 3.01. Results Of 12 016 adult samples that underwent both AOSM and mycobacterial culture, 19.0% (n = 2 288) were culture positive. NTM and MTBC accounted for 50.2% (n = 1 149) and 49.8% (n = 1 139) of the mycobacterial isolates, respectively. The diagnostic utility of AOSM for detecting NTM versus MTBC was 2.4% (95% CI 1.6%-3.5%) versus 53.6% (95% CI 50.6%-56.5%) for sensitivity, 93.8% (95% CI 93.3%-94.2%) versus 99.1% (95% CI 98.9%-99.3%) for specificity, 4.0% (95% CI 2.8%-5.8%) versus 86.4% (95% CI 83.8%-88.7%) for PPV and 90.1% (95% CI 90.0%-90.2%) versus 95.3% (95% CI 95.0%-95.6%) for NPV. Conclusions The diagnostic utility of AOSM was limited by poor sensitivity and PPV for NTM, and by poor sensitivity for MTBC. A positive AOSM result was a much more reliable indicator of the presence of MTBC than of NTM. In settings with a higher burden of TB than NTM disease, AOSM-positive patients with a clinical history suggestive of TB disease should be considered for TB treatment initiation while awaiting culture confirmation. In contrast, AOSM-positive patients whose clinical history is not strongly suggestive of TB—or is suggestive of NTM disease—should undergo additional testing using alternative methods, such as rapid molecular assays, that can reliably detect and distinguish between MTBC and NTM while awaiting culture confirmation.https://doi.org/10.1186/s12879-025-11298-3Auramine O smear microscopyDiagnostic utilityFluorochrome smear microscopyMycobacterium tuberculosis complexNon-tuberculous mycobacteriaTuberculosis |
| spellingShingle | Nadia Atiya Leong Tung Ong Thian Chee Loh Chee Kuan Wong Azwani Abdullah Diagnostic utility of auramine O smear microscopy for detecting non-tuberculous mycobacteria versus Mycobacterium tuberculosis complex in adult clinical samples: a 5-year retrospective study (2018–2022) BMC Infectious Diseases Auramine O smear microscopy Diagnostic utility Fluorochrome smear microscopy Mycobacterium tuberculosis complex Non-tuberculous mycobacteria Tuberculosis |
| title | Diagnostic utility of auramine O smear microscopy for detecting non-tuberculous mycobacteria versus Mycobacterium tuberculosis complex in adult clinical samples: a 5-year retrospective study (2018–2022) |
| title_full | Diagnostic utility of auramine O smear microscopy for detecting non-tuberculous mycobacteria versus Mycobacterium tuberculosis complex in adult clinical samples: a 5-year retrospective study (2018–2022) |
| title_fullStr | Diagnostic utility of auramine O smear microscopy for detecting non-tuberculous mycobacteria versus Mycobacterium tuberculosis complex in adult clinical samples: a 5-year retrospective study (2018–2022) |
| title_full_unstemmed | Diagnostic utility of auramine O smear microscopy for detecting non-tuberculous mycobacteria versus Mycobacterium tuberculosis complex in adult clinical samples: a 5-year retrospective study (2018–2022) |
| title_short | Diagnostic utility of auramine O smear microscopy for detecting non-tuberculous mycobacteria versus Mycobacterium tuberculosis complex in adult clinical samples: a 5-year retrospective study (2018–2022) |
| title_sort | diagnostic utility of auramine o smear microscopy for detecting non tuberculous mycobacteria versus mycobacterium tuberculosis complex in adult clinical samples a 5 year retrospective study 2018 2022 |
| topic | Auramine O smear microscopy Diagnostic utility Fluorochrome smear microscopy Mycobacterium tuberculosis complex Non-tuberculous mycobacteria Tuberculosis |
| url | https://doi.org/10.1186/s12879-025-11298-3 |
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