According to the World Health Organization ( WHO) there will be ten million new cases of tuberculosis this year in the developing world. But the good news is that effective therapy will prevent the deaths of many of these patients. However, by the time the sick patients are diagnosed and treated, they will have infected many others in their community. Indeed, this failure of interruption continues to keep the global epidemic alive and well. So prompt diagnosis is very important in the treatment of tuberculosis to help fight the spread of the disease.
The most widely used method to test the sputum for the tuberculosis bug is called the Ziehl Neelsen stain which is 125 years old. If this disease was still a major affliction in the Western world, to be sure there would have been new major breakthroughs in the diagnostic techniques, but basically tuberculosis is a poor man’s disease. Many people are seen who have a negative Ziehl Neelsen stain of their sputum which means that the tuberculosis bug was not detected in the sample. But it is possible that human error crept into the reading, that is the stain was not good enough and the technician missed the tuberculosis bug. Or the technician was in a hurry and did not read the sample properly. In addition it may be possible that there were so few organisms in the sample that even a good technician would miss this. Hence the Zihehl Neelsen technique is potentially fraught with errors if not carefully carried out.
So it was welcome news when a few months ago the WHO endorsed the GeneXpert device, a rapid test for TB as “a major milestone for global tuberculosis diagnosis”.
Unlike the Zehil Neilsen technique, the GeneXpert does not need anyone to be an expert in making the sputum slide and look for the bug under the microscope. Amazingly this new molecular approach is more straightforward. After the patient spits into a cup, the sample is placed in a “espresso” machine which examines the sample’s DNA to see if it contains the genetic signature of tuberculosis. A simple, reliable “yes” or “no “ answer is available in two hours. Importantly in this time frame, the GeneXpert can determine if the bacteria is resistant to rifampicin, the most effective of the four drug cocktail prescribed for tuberculosis. This knowledge allows the doctor to know from the start if they are dealing with resistant bacteria and thus tailor therapy accordingly.
However the initial cost of about $ 30,000 for the machine and at least $ 20 for the tests are daunting rates for the developing world. Unskilled workers can carry this test out with minimal training, but electricity is required. From hospitals in Bihar to the well appointed Hinduja Hospital in Mumbai, great satisfaction has been expressed about the usefulness and accuracy of the device. But the cost continues to be an important issue, regardless of the scientific enormity of the breakthrough. The WHO and other helpful parties are indeed trying to make the cost more affordable for people in the developing world where tuberculosis is rampant.