Molecular diagnosis of suspected tuberculosis from archived smear slides from the Balimo region, Papua New Guinea.

Tuberculosis (TB) is a serious health problem in Papua New Guinea (PNG) with an estimated 30,000 new cases and 3,800 deaths each year. In the Balimo region of the Western Province, the diagnosis relies on clinical manifestations and on the microscopic detection of acid-fast bacilli in sputum smears, a technique with limited sensitivity.We carried out a molecular diagnosis assay targeting DNA extracted from archived sputum smear slides collected from the Balimo region (2012-2014), without the need for a viable culture. The presence of Mycobacterium sp. was assessed using a qPCR approach from 1,162 slides prepared from 345 sputum samples.The qPCR technique identified the presence of mycobacteria from 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 compared to 206 qPCR-positive sputum overall.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 is even lower if nine patients diagnosed as extra-pulmonary tuberculosis are excluded from the analysis. However, the prevalence of false- negatives (AFB-negative/qPCR-positive) was high (28.5%).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.