Tuberculosis, a chronic bacterial air borne infection, is responsible for millions of active diseases and deaths globally despite an easy availability of cheap and effective treatment. Sputum of the infected person is the main cause of the spread of the TB infection. More than 90 per cent of infected patients with mycobacterium tuberculosis have asymptomatic latent infection. The risk of active disease is estimated to be approximately 5 per cent in the 18 months after initial infection and then approximately 5 per cent for the remaining lifetime. An estimated two billion persons worldwide suffer from latent infection and are at a greater risk of reactivation.
In 2011, 8.7 million new cases of active TB (out of these 13 per cent had co-infection with HIV) and 1.4 million deaths (out of these 4.3 lakhs are HIV infected patients) were registered. 3.1 lakh cases are of Multi Drug Resistant (MDR) TB registered worldwide.
Drug resistant TB is caused by inadequate drugs or doses or duration. It’s also caused in people contracting primary infection from resistant case. The failure to detect drug resistance results in the prescription of inappropriate treatment, increased mortality, treatment failure and further transmission of drug resistant TB. People with active TB suffer from symptoms like chronic cough for more than two weeks, sputum production, loss of appetite and weight, fever, night sweats and blood mixed sputum.
Diagnosis: AFB (Acid Fast Bacilli) Positive Sputum Culture is gold standard diagnosis of TB. If sputum sample is unavailable, then doctors use diagnostic aid like montoux test, FNAC (Fine Needle Aspiration Cytology) of any lymph node or biopsy. A new molecular diagnostic test called Xpert MTB/RIF assay detect Mycobacterium TB complex within two hours. It’s sensitivity and specificity seems to be very good for detection of TB. It also detects resistance to an antibacterial drug called Rifampicin.
Treatment of latent infection: People diagnosed with latent TB infection are suggested preventive treatment as they are at high risk of developing active TB. The preferred regimen is Isoniazid antibiotic (INH) for nine months but treatment is carried for longer duration in HIV infected persons in areas with high prevalence of TB. Only patients, with a positive TB test who are receiving preventive therapy with INH, showed lower rates of active TB and deaths.
Treatment of drug sensitive active TB: Effective TB treatment requires an accurate and early diagnosis, screening of DRT (Drug Resistant TB) and HIV, completing effective regimen which is generally six to nine months under expert supervision.
TB & HIV Infection: WHO recommends that ART therapy should be started within the first eight weeks after the initiation of TB treatment and patients with a CD 4 (blood count) plus cell count to be less than 50 receives ART within the first two weeks.
MDR TB: The treatment of MDR TB is based on expert opinion and requires a combination drugs regimen chosen from 1st and 2nd line ATT (Anti Tuberculosis Treatment). It’s associated with high risk of intolerance and serious toxic side effects. MDR TB should be given for minimum 20 months in person who have not received previous MDR TB treatment and for 30 months in those who have received previous MDR TB treatment.
XDR (Extensively Drug Resistant) TB: XDR TB is extremely difficult to diagnose and treat. In countries like India, where the disease is endemic, it’s associated with HIV infection can cause death up to 98 per cent.
Vaccination: It becomes imperative to vaccinate all the infants with BCG (M.bovis bacilli Calmette – Guerin) vaccine. The vaccine has displayed an estimated efficacy of approx 50 per cent in the prevention of the disease. Apart from vaccination, healthy and balanced diet, good hygiene practices are a must and avoid visiting TB clinics and hospitals. Also people who have been diagnosed with AFB positive sputum should wear mask and avoid direct contact with people.
The writer is senior consultant, Internal Medicine, Rockland Hospital.