Tests to detect Tuberculosis – An Update

Tuberculosis or TB is one of the earliest infectious diseases known to affect humans and it still ranks among the top life-threatening diseases. Despite several advancements in treatment and healthcare facilities, the situation is India is worsening every year. And the main reason behind it is development of drug-resistant TB (tuberculosis caused due to resistant strains of bacteria causing the disease).

drug-resistant-tuberculosis

Causes  and types of drug resistant TB

Tuberculosis is caused by the bacterium Mycobacterium tuberculosis. This bacterium is present in the atmosphere and can gain entry into your body when you breathe. But you may not develop an infection right away if you have a healthy immune system. In fact, the bacteria may have reached your lungs but your immune system would have contained the infection and prevented you from developing the disease. It is only when the immune system becomes too weak that the bacteria activate and causes the disease. Mycobacterium mainly attacks the lungs and resides there throughout the course of disease but it is capable of infiltrating almost any part of the body to create complications.

The main cause of developing drug resistance is patient non-compliance to TB treatment.

Dr Pradip Shah, consultant physician at Fortis Hospital, Mulund says ‘The treatment period of TB disease is usually 6-9 months. But, once patients start feeling better after taking medicines for 2 months or more they discontinue the treatment. This is one of the main pitfalls that we are facing in India.’

‘Once a TB patient stops taking the drugs, it gives an opportunity to TB bacteria to become resistant. Now these resistant bacilli that are still present in the affected patients get expelled into air which can be inhaled by any healthy individual. This is how challenging cases of multiple drug resistant TB (MDR TB) are increasing,’ says Dr Kapil Salgia, consultant pulmonologist.

Types of drug resistant TB:

Multiple drug resistant tuberculosis (MDR-TB ):  In clinical laboratory testing, if the TB causing organism is found to be resistant to the drugs isoniazid and rifampicn, then the person is said to be suffering from MDR-TB.

Extensively drug-resistant tuberculosis (XDR-TB): XDR-TB is defined as resistance developed to at least isoniazid and rifampicin, and also to any fluoroquinolone or second-line injectables like amikacin, capreomycin, and kanamycin.

Symptoms:

Drug resistant tuberculosis is no different from common tuberculosis. So the symptoms are the same

  • Bad cough persisting for 3 weeks or more
  • Chest pain
  • Coughing up blood or sputum (phlegm from deep inside the lungs)

Other symptoms of active TB disease include:

  • Weakness or fatigue
  • Weight loss
  • Lack of appetite
  • Chills
  • Fever
  • Sweating at night

Diagnosis of drug resistant TB

Dr Abha Shroff, chief pathologist and director at Disha Pathology Labs, Mumbai says ‘Tests for tuberculosis need to be carried out when the common symptoms last for more than 3 weeks and are found to be untreatable with commonly used medications and symptomatic treatments.’

Common tests like sputum test, Mantoux test, chest X Ray, complete blood count (CBC) are first used to diagnose whether a person is infected with TB. Once that is confirmed, the doctor needs to identify whether the patient is infected with drug-resistant strain of the organism that’s causing the disease. Here’s a detailed account about these diagnostic tests for TB.

Dr Shroff explains some advanced tests used to diagnose drug resistant TB.

  1. Xpert MTB/RIF (sputum):  This test provides simultaneous detection of both MTB and rifampicin resistance.
  2.  Genotype MTBDRplus V2, (sputum and culture material): This test provides results in 5 hours compared to other conventional methods that take 1 to 2 months. It allows early, appropriate treatment, which reduces transmission and spread of MDR-TB.
  3. MGIT Liquid Culture: It is a fully automated testing which identifies whether or not the sample is infected along with susceptibility testing for the disease causing organism.

‘These advanced tests are available now in India at cheaper rates and all IPAQT member labs are allowed to offer these tests,’ she says. Here’s the cost for each of the test:

  • Xpert MTB/RIF – Rs 1700
  • Genotype MTBDRplus – Rs 1600
  • MGIT Liquid Culture – Rs 900

Treatment and management

According to the World Health organization (WHO), XDR-TB reduces the treatment options to a great extent but there are a few ways to manage it. There are some groups of drugs that are active against tuberculosis but are not usually recommended for the treatment of MDR-TB. These include clofazimine, linezolid, amoxicillin/clavulanate, clarithromycin and high-dose isoniazid.

Right now, preventing the spread of drug-resistant TB is the most difficult challenge facing India. Factors like delayed diagnosis, incomplete treatment and lack of patient counseling greatly contribute to increasing cases. Dr Shah explains some ways to overcome these challenges:

  •  Explore new drugs:  The recent case, where a TB patient was treated with anti-leprosy drug is a good opportunity to focus on new drugs. Our government should look into the potential of anti-leprosy drugs in treatment of drug resistant cases of TB and make it available for everyone.
  • Creating national awareness: We need a stringent protocol for diagnosis and treatment of TB. With that we can have more programmes aimed at controlling TB on a national level.
  •  Cheaper drugs: Right now TB treatment costs about Rs 5000 to 7000 every month. Patients in remote parts of the country may not able to afford the treatment. So, they either stop taking the drugs or switch to lower quality of drugs that do not provide relief. This increases the chances of resistance. Hence, both TB drugs and diagnostic tests should be made affordable at all levels, without compromising the quality.