Dr. Shalu Verma Kumar, CORE Diagnostics
Tuberculosis (TB) is an infectious disease variously named consumption, white plague, phthisis, or scrofula. It has been rampant in India, with the first cases being reported as early as 1500 BCE. As we celebrate the WHO World TB Day on 24 March 2018, we need an up-to-date assessment of our efforts to control TB. In 2016, 10.4 million people world-wide became ill with TB, with ~1.7 million people dying of it. As per the Global TB Report 2017, a whopping 26% of these deaths (4.23 lakhs) were reported from India. The incidence of TB in India remains high—2.790 million patients in 2016. However, the incidence has declined during the 2000-2016 period, such that the rate (2016) stood at 211/100000 population/year. India led the world in notification of new TB cases, with a 37% increase during the 2013–2016 period. The issues of HIV/AIDS, and multi-drug-resistant tuberculosis (MDR-TB) further complicate TB control in India. The government of India initiative ‘Revised National Tuberculosis Control Program’ (RNTCP) is tasked with TB control in India. India allocated US$ 525 million for TB prevention, diagnosis, and control in 2017. Plans are afoot to carry out a national TB prevalence study in 2018.
Tuberculosis is caused by one of several bacteria belonging to the Mycobacterium tuberculosis complex (MTBC). Of these, Mycobacterium tuberculosis is the most important causative agent. One third of the world’s population is infected with this bacterium. Those infected may either carry latent TB (these people do not feel sick, do not have any symptoms, can’t spread TB, and are usually positive in PPD skin test), or show active disease. Symptoms of active TB include coughing that lasts ≥3weeks, chest pain, or coughing up of blood, and sputum. Early symptoms may include unexplained weight loss, fever, fatigue, weakness, night sweats, chills etc. Infection spreads when you breathe TB bacteria shed into air by a patient with active disease. Such patients can spread disease by coughing, sneezing, or simply talking. Approximately 10% of people with latent TB infection, go on to develop active TB disease. People with compromised immune system (such as HIV/AIDS patients), those who inject illicit drugs, and who have past history of inadequately treated TB have increased risk of progression to active TB disease.
Diagnosis starts with a physical examination wherein a doctor examines your lungs with a stethoscope, and checks your lymph nodes for swelling. He/she may next order a chest X-ray or a CT scan which may show white spots (granulomas) in your lungs where your immune system has trapped TB bacteria. Should the chest X-ray be suggestive of TB, your doctor may take samples of your sputum (the mucus brought up by coughing). This is examined under the microscope, and also cultured to find out the strain of bacteria, and which antibiotics are effective. The commonest TB test is a simple skin test called the Mantoux test. In this, the physician injects a substance called PPD tuberculin into your arm. A swelling or bump at the site of injection post 48 to 72 hours shows that you are likely to have TB. Nucleic Acid Amplification Tests are routinely used in TB diagnosis. The US Food and Drug Administration (FDA) has approved QuantiFERON-TB Gold Plus (QFT-Plus).
Treatment of TB is immensely possible. It requires close cooperation between the patient, and the physician. The treatment lasts at least 6 months in duration, but may extend to 12 months. Treatment involves taking one, or several different antibiotics. The most common antibiotics prescribed are Isoniazid (INH), Rifampin (RIF), Ethambutol, and Pyrazinamide. For a person with latent tuberculosis, the doctor might treat you with isoniazid for at least six months. The side-effects of these drugs may include lack of appetite, nausea, vomiting, abdominal pain, skin rashes, joint-pain, blurred/changed vision, ringing in ears, hearing loss etc. However, it is dangerous to discontinue your TB drugs, or not take them regularly. The Tb bacteria could continue to proliferate in your body, and even develop resistance to the prescribed drugs. Thus, drug resistant TB evolves when you are infected with a TB strain that is resistant to one or more of the standard antibiotics. Drug resistant TB is more frequently encountered in people who do not take their prescription drugs regularly or as prescribed, are in close contact with a patient with drug-resistant TB, have relapsed disease, or hail from areas where drug-resistant TB is common.
Patients resistant to isoniazid (INH) and rifampin (RIF) are said to harbour MDR-TB. In 2016, there were 147,000 such patients in India, with an incidence rate of 11/100000 population/year. Patients with MDR-TB are treated with several antibiotics each day for up to two years, but mortality rate in such patients remains high. About 6.2% of MDR-TB cases worldwide have extensively drug-resistant TB (XDR-TB). Patients with XDR-TB are resistant to at least four anti-TB drugs. Such patients in addition to being resistant to INH and RIF, are resistant to fluoroquinolones (such as levofloxacin or moxifloxacin) and to at least one second-line drug (amikacin, capreomycin or kanamycin). Once treatment of such patients is initiated, isolation is usually neither necessary nor appropriate.
Tuberculosis control shall entail a sustained commitment by scientific, political and social authorities in India.