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Updated: Aug 6, 2026
The MODS method for diagnosis of tuberculosis and multidrug resistant tuberculosis
Published on: August 11, 2008
Method for efficient storage and transportation of sputum specimens for molecular testing of tuberculosis
1Department of Infectious and Respiratory Diseases, Graduate School of Medicine, Tohoku University, Sendai, Japan.
Setting:
The polymerase chain reaction (PCR) is a highly sensitive method for the detection of Mycobacterium tuberculosis and is available in most countries, though to a lesser extent in rural areas.
Objective:
To amplify M. tuberculosis DNA sequences of sputum spotted on FTA cards and compare them with the results of microscopic examination among culture-positive samples.
Design:
A total of 102 sputum specimens of TB patients in treatment were spotted on FTA cards and stored at room temperature until DNA analysis. We assessed the IS6110 region of M. tuberculosis. The efficacy of the PCR assay for the direct detection of M. tuberculosis was evaluated and compared with the results of cultures (Middlebrook 7H9 broth) and smears of fresh sputum specimens.
Results:
We were able to detect 10 fg/microl of mycobacterial DNA even after 6 months in storage. The PCR sensitivity and specificity using the FTA card system were 82% and 96%, while microscopic examination showed 41% and 95%, respectively.
Conclusion:
The FTA card system for the storage of bacterial DNA from sputum samples should be considered for the molecular diagnosis of tuberculosis. Samples can easily be obtained from geographically isolated populations and shipped by mail for accurate molecular diagnosis.
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