Source: Annual Congress 2008 - Genetics, immunology and microbiology of tuberculosis
Disease area: Respiratory infections



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A. Cannas, L. Calvo, T. Chiacchio, G. Cuzzi, R. Urso, F. Noto, S. Grisetti, M. Di Marco, A. Gualano, D. Goletti, E. Girardi (Rome, Italy). Mycobacterium tuberculosis DNA detection in urine samples from pulmonary tuberculosis patients. Eur Respir J 2008; 32: Suppl. 52, 4527

Member's Comments

Angela Cannas - 08.10.2008 08:19
Treatment monitoring and renal TB exclusion
We have data on TB Tr-DNA analysis at 2 months after start of treatment, where the signal is not present anymore. We are organizing at the moment a study of evaluation of Tr-DNA assay for therapy monitoring. The exclusion of renal involvement in these patients is based on clinical and microbiological diagnosis (urine culture).

Paul Kelly - 07.10.2008 10:18
P Kelly
Very interesting experiment. Do the DNA fragments disappear during treatment ? In patients in whom mycobacterial DNA was detected in urine how certain are you that they do not have GU tract/renal TB ? Are all these DNA fragments small enough to pass in glomular filtration ?

Angela Cannas - 06.10.2008 15:25
Details on Tr-DNA study
Thanks for the comments. Here the answers: 1. The non invasiveness would definitely be the biggest advantage of a test run on urine specimens, especially in situations characterized by difficulties in obtaining a sputum sample, as in children. 2. Sensitivity of the test, at the moment, is low, if compared with tests that use sputum specimens. We look for a very small amount of DNA , supposing that this DNA comes to the urine from a distant site (ex. lungs). The hypothesis is that bacterial DNA undergoes fragmentation and a portion of these fragments is transported through blood and renal barrier. 3. I agree with your suggestion to compare to other molecular assays, and we'll plan further studies including this aspect. 4. We are moving forward our studies, in two directions: a) to study a larger number of TB patients, based on enrollment of high suspect of pulmonary and extra-pulmonary TB patients. This will lead to increase the number of AFB and culture neg TB. B) to improve the test technically: we are at the moment developing a Real-Time amplification-based test, being aware of limitations of a semi-nested PCR assay.

Massimo Amicosante - 04.10.2008 10:37
Diagnostic Consideration
The only advantage that I see in the study reported that the sample to identify MTB specific DNA is coming from a non invasive procedure. The sensitivity reported for the Tr-DNA (34/43, 79%) is significantly lower than the sensitivity of the amplification performed (35/37, 96%) on other speciments (I suppose sputum or other pulmonary samples if I have well understood table 1), p=0.039. Further, the study was performed in a group of TB patient that were almost all AFB-positive (41/43) where usually the molecular tests on pulmonary derived speciments are performing very well (as also demonstrate by the data on the Table 1) and the potential clinically usage of the Tr-DNA assay seems to be suboptimal even using a detection system potentially very sensitive (as well as critical for being used in standard clinical laboratory conditions) like a semi-nested PCR. I would suggest to comments these points, to present the data in comparisons with the other molecular assay performed and to enlarge the study to AFB-negative subjects.

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