Detection of Mycobacterium tuberculosis from sputum collected on filter paper and stored at room temperature for 5 days by PCR assay and culture.

UNLABELLED: The efficacy of PCR assay and culture for direct detection of M. tuberculosis (MTB) from sputum specimens collected on filter paper and stored at room temperature for 5 days was evaluated in comparison with conventional culture of fresh sputum specimen. A total of 231 sputum specimens were examined. MTB was recovered from 124 samples by culture from fresh sputum samples before storage. The culture positivity rate was significantly decreased to 70 per cent after 5 day's storage on filter paper. For PCR assay, a fragment of 377-bp of the IS6110 sequence was amplified and detected using nested PCR. Compared with culture results performed on fresh sputum samples, the sensitivity, specificity, and efficiency for the nested PCR were 96.0, 97.2 and 96.5 per cent, respectively. The nested PCR showed sensitivity and specificity with no significant difference (p>0.05) from culture of fresh sputum specimens.
CONCLUSION: The collection and storage of sputum on filter paper at room temperature for 5 days had no apparent effect on the performance of nested PCR. Sputum samples collected by this method could be sent by post in a minimum of space and inexpensive way and will enable a large number of samples collected in the field or from peripheral health centers to be sent to central laboratories for analysis by trained technicians and under a well-equipped and well-established quality control system. The rapid and reliable detection by PCR-based assay will be helpful for optimal patient management of therapy and effective control of tuberculosis.