Hains Mycobacterium Tuberculosis 1st & 2nd Line Drug Resistance Test

HAINS Mycobacterium Tuberculosis First and Second Line Drug Resistance Test

This test is used to detect tuberculosis and its resistance to certain anti-tuberculosis medications in your sputum sample or any other clinical sample. This test is also called line probe assay first and second line TB test. Tuberculosis (TB) can be caused by various species of bacteria (mycobacterium) together called mycobacterium TB complex (MTB complex).the species included in MTB complex are M.tuberculosis, M.bovis, M.africanum, M.microti, M.canetti and M.pinnipidi.

This disease is highly infectious (spreads from one person to another through tiny droplets) and predominantly affects the lungs. Tuberculosis is more common in people infected with HIV (human immunodeficiency virus).

The common symptoms of active pulmonary (lungs) TB are:

• Prolonged coughing for 3 weeks or more
• Blood in cough
• Chest pain, painful breathing, pain while coughing
• Unexplained Weight loss
• Fever with evening rise
• Loss of appetite
• Night sweats

The other less common sites which can be infected with tuberculosis are spine, brain, intestine, genitals, kidneys, joints, liver etc. Tuberculosis treatment includes intake of many drugs which have to be taken for prolonged time duration. The common drugs used for the treatment of tuberculosis are classified as first line drugs and second line drugs.

The first line drugs are:

• Isoniazid
• Rifampicin
• Ethambutol
• Pyrazinamide
• Streptomycin

MDR TB is caused by mycobacterium that is resistant to at least two first line drugs Isoniazid and Rifampicin.

In MDR TB second line drugs are used such as:

• Fluoroquinolones
• Kanamycin
• Amikacin
• Capreomycin

The resistance to these first line and second line drugs occur due to mutations in certain mycobacterium genes. This test thus identifies drug resistance by identifying mutations in mycobacterium genes along with the detection of Mycobacterium Tuberculosis complex.

Why is HAINS Mycobacterium Tuberculosis first and second line drug resistance test prescribed?

Your health care provider may advise this test to get rapid and reliable diagnosis of MTB complex if clinically suspected. If MTB complex is detected it also identifies MDR TB. Thus this test is useful for prompt diagnosis and appropriate treatment of tuberculosis. This helps in reducing relapse rate, spread of MDR tuberculosis and amplification of drug resistance. This test is also useful in those patients with failed treatment and relapse.

What are the components of line probe assay first and second line TB?

This test includes the following:

• Identification of MTB complex
• Line probe assay first line detects
• Identification of Isoniazid resistance by detecting mutation in katG gene and inhA gene
• identification of Rifampicin resistance by detecting mutation in rpob gene
• Line probe assay second line detects
• Subunit A of DNA gyrase (gyrA locus) ±G88A, G88C, A90V, S91P, D94A, D94N, D94Y, D94G mutations confer resistance to Fluoroquinolones.
• 16srRNA gene detects resistance to Aminoglycosides. A1401G mutation confers resistance to Capreomycin, Amikacin & Kanamycin ; C1402T mutation confers resistance to Capreomycin,Viomycin & Kanamycin; G1484T mutation confers resistance to Capreomycin, Amikacin, Viomycin & Kanamycin.
• Arabinosyl transferase (embB locus)±M306I / M306V mutations confer resistance to Ethambutol.

Procedure and prerequisites

It is a type of nucleic acid amplification test (NAAT). Its result should be interpreted with clinical, radiographic and other test findings. The sample taken for this test depends upon the site of involvement such as sputum (pulmonary TB), pleural fluid, blood, bone marrow, tissue biopsy, CSF (cerebrospinal fluid).

Reference range

The result can be MTB complex detected or not detected. If detected resistance to first line and second line drugs detected or not detected. The result can also be inhibitory which indicates presence of inhibitors in submitted samples. In that case culture test is recommended.