Vanina Guernier1, Tanya Diefenbach-Elstob2, Daniel Pelowa3, Sandra Pollard4, Graham Burgess5, Emma S McBryde6, Jeffrey Warner7. 1. Australian Institute of Tropical Health and Medicine, James Cook University, Townsville, Queensland, Australia. Electronic address: vanina.guernier@gmail.com. 2. Australian Institute of Tropical Health and Medicine, James Cook University, Townsville, Queensland, Australia; College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, Queensland, Australia. Electronic address: tanya.elstob@my.jcu.edu.au. 3. Balimo District Hospital, Balimo, Western Province, Papua New Guinea. 4. College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, Queensland, Australia. Electronic address: sandra.pollard@jcu.edu.au. 5. College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, Queensland, Australia. Electronic address: graham.burgess@jcu.edu.au. 6. Australian Institute of Tropical Health and Medicine, James Cook University, Townsville, Queensland, Australia; Department of Medicine, Royal Melbourne Hospital, University of Melbourne, Melbourne, Victoria, Australia. Electronic address: emma.mcbryde@jcu.edu.au. 7. Australian Institute of Tropical Health and Medicine, James Cook University, Townsville, Queensland, Australia; College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, Queensland, Australia. Electronic address: jeffrey.warner@jcu.edu.au.
Abstract
BACKGROUND: Tuberculosis (TB) is a serious health problem in Papua New Guinea (PNG) with an estimated 30000 new cases and 3800 deaths each year. In the Balimo region of the Western Province, diagnosis relies on clinical manifestations and on the microscopic detection of acid-fast bacilli (AFB) in sputum smears, a technique with limited sensitivity. METHODS: A molecular diagnosis assay targeting DNA extracted from archived sputum smear slides collected from the Balimo region (2012-2014) was conducted, without the need for a viable culture. The presence of Mycobacterium sp on 1162 slides prepared from 345 sputum samples was assessed using a real-time PCR (qPCR) approach. RESULTS: The qPCR technique identified the presence of mycobacteria in 35.4% of the smear slides and 59.7% of the tested sputum samples. Poor agreement was observed between the two diagnosis methods (smear AFB microscopy versus qPCR), with 100 AFB-positive sputum samples compared to 206 qPCR-positive sputum samples overall. Treatment was initiated in 90.2% of the smear-positive cases. Unnecessary treatment of 'false-positive' TB cases (AFB-negative/qPCR-negative) was very low (8.6%) and was even lower when the nine patients diagnosed with extrapulmonary TB were excluded from the analysis. However, the prevalence of false-negatives (AFB-negative/qPCR-positive) was high (28.5%). CONCLUSIONS: Undetected smear-negative TB is occurring in the Balimo region of PNG, as well as some unnecessary empirical treatment. Molecular methods of diagnosis could greatly reduce the frequency of inappropriate clinical assessment, as well as providing point-of-care diagnosis. This may provide substantial patient and programmatic benefits, including lowering the economic burden on patients from rural areas seeking medical diagnosis in Balimo.
BACKGROUND:Tuberculosis (TB) is a serious health problem in Papua New Guinea (PNG) with an estimated 30000 new cases and 3800 deaths each year. In the Balimo region of the Western Province, diagnosis relies on clinical manifestations and on the microscopic detection of acid-fast bacilli (AFB) in sputum smears, a technique with limited sensitivity. METHODS: A molecular diagnosis assay targeting DNA extracted from archived sputum smear slides collected from the Balimo region (2012-2014) was conducted, without the need for a viable culture. The presence of Mycobacterium sp on 1162 slides prepared from 345 sputum samples was assessed using a real-time PCR (qPCR) approach. RESULTS: The qPCR technique identified the presence of mycobacteria in 35.4% of the smear slides and 59.7% of the tested sputum samples. Poor agreement was observed between the two diagnosis methods (smear AFB microscopy versus qPCR), with 100 AFB-positive sputum samples compared to 206 qPCR-positive sputum samples overall. Treatment was initiated in 90.2% of the smear-positive cases. Unnecessary treatment of 'false-positive' TB cases (AFB-negative/qPCR-negative) was very low (8.6%) and was even lower when the nine patients diagnosed with extrapulmonary TB were excluded from the analysis. However, the prevalence of false-negatives (AFB-negative/qPCR-positive) was high (28.5%). CONCLUSIONS: Undetected smear-negative TB is occurring in the Balimo region of PNG, as well as some unnecessary empirical treatment. Molecular methods of diagnosis could greatly reduce the frequency of inappropriate clinical assessment, as well as providing point-of-care diagnosis. This may provide substantial patient and programmatic benefits, including lowering the economic burden on patients from rural areas seeking medical diagnosis in Balimo.
Authors: Tanya Diefenbach-Elstob; Vanina Guernier-Cambert; Bisato Gula; Robert Dowi; Daniel Pelowa; William Pomat; Catherine Rush; David Plummer; Emma McBryde; Jeffrey Warner Journal: Western Pac Surveill Response J Date: 2019-12-26