What is drug-resistant TB? How to detect drug-resistant TB?

Posted by Master, Doctor Nguyen Ngoc Phu - ICU Doctor - Intensive Care Department - Vinmec Times City International General Hospital

Currently, Vietnam is one of 30 countries with a high rate of drug-resistant tuberculosis in the world. The disease is not only easy to catch but also causes many difficulties in the treatment process. So how to detect drug-resistant TB?

Drug-resistant TB is when a patient is suspected of drug resistance while being treated for TB, but the symptoms of fever, cough, and sputum production do not improve or subside for a while and then reappear with increasing symptoms, The patient continued to lose weight.
However, drug-resistant TB can be diagnosed in people who have never had TB and the clinical symptoms of MDR-TB may not be different from those of regular TB. Based on the results of antibiogram or WHO-certified rapid diagnostic tests (Hain test, Xpert MTB/RIF...), diagnostic criteria for drug-resistant tuberculosis are determined as follows:
Prescription-resistant TB: Resistant to only one other first-line anti-TB drug Rifampicin Multidrug-resistant TB: Resistance to two or more first-line anti-TB drugs but not to Rifampicin Multidrug-resistant TB (MDR-TB): Concomitant use with at least two anti-TB drugs, Isoniazid and Rifampicin Pre-Superresistant: MDR TB has additional resistance to any fluoroquinolone drug or to at least one of the three second-line injectable drugs Capreomycin, Kanamycin, Amikacin, not both types added at the same time). Super-resistant (XDR-TB): MDR-TB has additional resistance to any of the fluoroquinolones and any of the three second-line injections (Capreomycin, Kanamycin, Amikacin).

Based on risk factors, clinical and subclinical helps to detect drug-resistant TB patients to have appropriate treatment regimen. Plan II (recurrent TB regimen) Suspected TB patient or recent contact with a patient with drug-resistant TB Patients who have failed regimen I Treatment with no sputum negative after 2 or 3 months of regimen Plan I or II People with suspected TB relapse or patients with relapsed TB (Rule I or II) Suspected TB treated after quitting treatment or TB patients re-treated after quitting treatment (Rule 1 or 2) Patient newly discovered HIV (+) Other cases: include suspected TB patients or TB patients with a history of taking TB drugs for more than 1 month, suspected TB patients or TB patients with a history of TB treatment in private health but The outcome of the treatment is unknown. New TB patient (HIV negative or unknown)

2.2 Clinical signs and symptoms suggestive of tuberculosis The patient was on TB treatment but the symptoms of fever, cough, and sputum expectorant did not improve or subside for a while and then reappear with symptoms. increased, the patient continued to lose weight. Sometimes drug-resistant TB can be diagnosed in a person who has never had TB, and the clinical presentation of MDR-TB may not be different from that of regular TB.

AFB test, culture is positive continuously or negative for some time, then positive again or negative, alternately positive in people on TB treatment.
Antibiogram test shows resistance to first- and second-line anti-TB drugs. Molecular biology techniques can quickly diagnose multidrug-resistant TB: Hain test, Xpert MTB/RIF.
The image of lesions on the chest X-ray film does not change or new lesions appear during the correct treatment with a controlled regimen. Cases of drug-resistant TB were found in people who had never had regular TB.

4.1 Principles of protocol development The regimen should have at least 5 effective drugs, including 4 main second-line TB drugs (1 class A drug, 1 class B drug, at least 2 group C drugs) and pyrazinamide. In case there are not enough effective drugs to develop the above regimen, drugs of groups D2, D3 can be used to ensure enough 5 drugs. When the patient is resistant to FQs (group A) or drugs second-line injection (group B), it is necessary to replace other drugs, but still follow the same principles as for R/MDR-TB resistant patients. Using injectable drugs is still sensitive and can be used for a long time (12). month or during the course). If resistance to all injectable drugs is present, the use of drugs that the patient has never used or does not use injections is recommended. Using new generation Fluoroquinolone. Consider using new drugs according to WHO recommendations and guidelines (Bedaquiline, Delamanid). Consider high-dose isoniazid if anti-KAT results or low H-antibody results.

4.2. Some regimens to treat drug-resistant tuberculosis 4.2.1. Standard short-term regimen for multidrug-resistant TB 4-6 Km Lfx Pto Cfz Z H high dose E / 5 Lfx Cfz Z E
4.2.2. Standard regimen 20 months 8 Km (Cm) Lfx Pto Cs Z/12 Lfx Pto Cs Z
4.2.3. Pre-super resistance regimen The main principle is to replace resistant drugs with effective drugs (listed in the drug classification table for drug-resistant TB – WHO 2016) and to follow the general principle (at least 5 drugs are effective). effective, including 4 leading second-line TB drugs and pyrazinamide.D2 and D3 drugs can be used to ensure all 5 drugs are effective)
4.2.4. Super-resistant regimen The principle of developing a regimen is similar to that of pre-super-resistant patients. However, because patients are already resistant to both FQs and second-line drugs, it is more difficult to choose an effective drug, especially for patients who have used most of the second-line drugs in the past. long-term availability or recurrence, failure of multidrug regimens. Priority should be given to the use of new drugs with the highest effectiveness, while further strengthening the monitoring of treatment, management of adverse reactions, thorough counseling for patients to ensure compliance with guideline 57 to achieve the best treatment outcome, as this is the patient's last chance for treatment.

4.2.5. Individual regimen Subjects enrolled, R/MDR-TB-resistant TB did not meet the criteria for standard regimens, including:
Meningococcal tuberculosis (depending on age, treatment history) Pregnant or nursing women Breastfeeding Severe multidrug-resistant pulmonary tuberculosis, intolerance, hypersensitivity, risk of drug toxicity (drug interactions) with any drug in the regimen.
Some special cases need to adjust the dose of drugs or should not use some drugs: Patients with QT interval >=500ms on electrocardiogram, liver failure, kidney failure, diabetes mellitus, epilepsy, neuritis optic nerve and peripheral nerve.

Principle, replace intolerant or unsuitable drugs with other drugs and ensure “at least 5 effective drugs, including 4 effective second-line TB drugs (1 class A drug, 1 B, at least 2 class C drugs) and pyrazinamide. In case there are not enough effective drugs to develop the above regimen, drugs of groups D2, D3 can be used to ensure enough 5 drugs.
Currently, drug-resistant TB in our country is on the rise. Therefore, in addition to diagnosing the disease to have a timely treatment plan, adherence to the treatment regimen is also extremely important.
Vinmec International General Hospital has a team of doctors in medical examination and treatment with many years of experience. In addition, modern facilities and equipment will serve the examination process to help bring the best results to patients.