Innovations in Tuberculosis Diagnosis and Drug Resistance
Tuberculosis (TB) is one of the world’s deadliest infectious diseases, causing around 1.6 million deaths each year. It spreads mainly through the air when a person with TB coughs or sneezes. Though it usually affects the lungs, it can also spread to other parts of the body, especially in people with weak immune systems.
Early diagnosis and treatment are crucial to stop the spread of TB. Unfortunately, 36% of TB cases go undetected globally.
How TB is Diagnosed
Doctors test for TB using samples like sputum (mucus from the lungs), nasal secretions, or fluids from the stomach. In children, stool samples are now being used more often, as they are easier to collect.
In most low-income countries, doctors still rely on a basic test called smear microscopy. It uses a microscope to detect TB bacteria but misses around 40% of cases. Better methods like cultures and molecular tests (which detect the DNA of TB bacteria) are more accurate but may not be widely available.
Newer and Faster TB Testing Methods
Modern technology is making TB testing faster and more accurate:
Liquid cultures grow TB bacteria faster than traditional methods.
PCR (Polymerase Chain Reaction) and DNA tests can detect TB bacteria in just a few hours.
LED microscopes are replacing older models for better results.
Stool tests for children using special kits are now available and effective.
LAM urine tests help detect TB in people with HIV and weak immune systems.
Improvements in Diagnosing TB in Children
Children often can’t provide sputum for testing. New methods use stool samples with automated machines like GeneXpert to find TB bacteria. These tests are easy to perform and don’t need special lab equipment.
Better Microscopes for Detecting TB
Traditional light microscopes have limited accuracy. New fluorescence microscopes (especially LED-based ones) make TB bacteria easier to see and are more sensitive. These are now affordable and approved by the World Health Organization (WHO).
TB Culture Methods
Growing TB bacteria in a lab culture is still the gold standard. It takes time (2–8 weeks), but it’s very accurate. Liquid culture systems, such as MGIT 960, can give results in about 10–14 days. These systems are becoming more widely used and accepted.
Rapid Tests Using Urine (LAM)
LAM tests detect a substance from TB bacteria in urine. They are fast and can be done at the patient’s bedside. Although not perfect, they are useful in HIV-positive patients and are being improved.
Blood Tests and New Research
New blood tests use advanced technologies like Immuno-PCR and aptamer-based tests to improve accuracy. These are still being researched but show promise, especially in difficult-to-diagnose cases.
Detecting Latent TB (No Symptoms)
Some people carry TB bacteria without symptoms (latent TB). They are not sick but can develop TB later. Tests like the Mantoux skin test and blood-based IGRAs help detect this. However, they can give false results, especially in people with weak immune systems or recent vaccinations.
DNA Testing and NAATs
Nucleic Acid Amplification Tests (NAATs) use DNA to detect TB bacteria quickly. Commercial kits like Gene-Probe, Roche Amplicor, and BD-ProbeTec can identify TB in respiratory samples within hours. However, they are less reliable for samples from other body parts and sometimes less sensitive than culture tests.
Why Testing for Drug-Resistant TB Matters
TB bacteria can become resistant to antibiotics, making treatment much harder. Tests for drug resistance help doctors choose the right medicine early. Traditional methods take weeks, but newer tests like MODS, TLA, and Colorimetric Redox Indicator (CRI) methods give results in 1–2 weeks. These use color changes or microscope checks to detect resistant bacteria.
Automated Testing Systems
Modern systems like BACTEC MGIT 960 detect TB bacteria by measuring oxygen use. They are faster, more accurate, and can test for resistance to common TB drugs.
Bottomline: TB diagnosis has come a long way. From simple microscopes to rapid DNA tests and automated machines, we now have better tools to find TB faster and treat it more effectively. However, access to these tools remains limited in many parts of the world.
Improving laboratory capacity, training, and affordability is essential to stop TB and prevent the spread of drug-resistant forms. Raising awareness and using these modern methods wisely can save countless lives.
Dr Javeed Kakroo is a Microbiologist, Certified Infection Control Auditor, Kidney Hospital, Srinagar
