Tuesday, January 11, 2011

New diagnostic test of TB - few questions

From public health perspective, it is critical to timely diagnoze and cure the infectious TB (sputum positive pulmonary TB) because this form of TB is responsible in discharging the bacteria in the environment and making others susceptable to TB through airborne transmission. Children, elderly and those with low level immunity (HIV, prolong steroid, anti-cancer therapy, malnutrition, diabetes, chronic smokers, alcohol) are much more prone to TB disease in the high TB burden set-ups. Sputum microscopy is the best diagnostic technique so far to diagnoze infectious TB, readily avilable in the public health systems and very cheap. But it is also not fully effective to detect all the infectious TB cases (improper sputum collection, faulty slide preparation, lab technician error) and not at all effective to detect non-infectious form of TB (EP TB). Here, we have to remember one thing that EP TB is important to detect and treat in time to reduce TB related mortalities but it has no impact to break the transmission of TB.
Timely diagnosing and treatment of infectious TB is effective to reduce the overall TB load in the community and subsequently impacts on reducing the incidences of EP TB as well. 
The success of TB control depends primarily on
1) Detection of infectious TB
2) High quality sputum microscopy to detect infectious TB in maximum numbers (or to miss in minimum numbers)
3) Quality treatment with adherence to DOTS
All these interventions are associated with a number of operational issues. I don't like to highlight them once again because they have been discussed so many times in so many forum. 
Now my questions:
1) Will the new diagnostic have the potential to replace sputum microscopy?
2) Will it be cost effective enough to be scaled up in the public health system of a low/middle income country after a successful pilot trial?
3) How much it will be effective to take care of the operational issues as mentioned above?

Sugata Mukhopadhyay
Universal Health

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