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Tuberculosis
Active tuberculosis is diagnosed in sputum (smear, PCR and culture) and treated for 6 months — 2 months of four drugs (RIPE) followed by 4 months of rifampicin and isoniazid; latent tuberculosis is diagnosed with a TST or IGRA and treated only after active disease has been excluded.
Why it matters in the exam
Tuberculosis questions present a cough of more than three weeks, fever, night sweats, weight loss and sometimes haemoptysis, with an upper-lobe infiltrate or cavity on the chest film, in a person from a risk group: an immigrant from a country where tuberculosis is common, a person with HIV, a prisoner, a homeless person, a person with diabetes or silicosis, or a patient on anti-TNF therapy. The correct steps: airborne isolation, three sputum samples for smear and culture, and a PCR test (Xpert MTB/RIF) that also detects rifampicin resistance. In Israel tuberculosis is a notifiable disease, and treatment is given under directly observed therapy (DOT).
Many questions deal with side effects: isoniazid — hepatitis and peripheral neuropathy (hence pyridoxine); rifampicin — orange body fluids and enzyme induction that weakens contraceptive pills, warfarin and HIV drugs; pyrazinamide — liver injury and high uric acid; ethambutol — optic neuritis with loss of red-green colour vision. In latent tuberculosis: a TST of 5 mm or more is positive in immunosuppressed people and close contacts, and 10 mm or more in immigrants and health workers; before treatment a chest film is done, then 3 months of isoniazid with rifapentine, 4 months of rifampicin or 6–9 months of isoniazid are given.
Key points
- Diagnosis: 3 sputum samples, PCR (Xpert) and culture, in airborne isolation.
- Standard treatment: 2 months RIPE and 4 months RH — 6 months in total.
- Isoniazid: neuropathy (pyridoxine); ethambutol: colour vision; rifampicin: orange and enzyme induction.
- Latent: TST or IGRA, chest film to exclude active disease, then 3 or 4 months of treatment.
- Screening for latent tuberculosis is mandatory before anti-TNF therapy.
Summary table
| Situation | Diagnosis | Treatment | Exam note |
|---|---|---|---|
| Active pulmonary TB | 3 sputum samples: smear, PCR (Xpert) and culture | 2 months RIPE followed by 4 months RH | Airborne isolation, DOT, notifiable |
| Isoniazid | Hepatitis, neuropathy | Pyridoxine to prevent neuropathy | Liver tests in risk groups |
| Rifampicin | Orange fluids, enzyme induction | Adjust contraceptive pills, warfarin and HIV drugs | Also hepatitis |
| Pyrazinamide and ethambutol | PZA: liver, uric acid; EMB: colour vision | Eye test before ethambutol | Reduce the dose in kidney failure |
| Latent TB | TST: 5 mm or more in immunosuppressed and contacts; 10 mm or more in immigrants; or IGRA | 3 months isoniazid + rifapentine, or 4 months rifampicin | Exclude active disease with a chest film |
| Before anti-TNF | TST or IGRA and chest film | Treat latent infection before starting the drug | Also before transplant and dialysis |
A free exam question
מה מזהה בדיקת Interferon- Release Assay ( IGRA ?) (the question as examined, in Hebrew)
- א. מצב של Latent Tuberculosis
- ב. מצב של Active tuberculosis
- ג. עמידות של HIV לתרופות אנטירטרוויראליות
- ד. עמידות של HCV לתרופות אנטיויראליות
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Sources
- Official ATS/CDC/ERS/IDSA Clinical Practice Guidelines: Treatment of Drug-Susceptible Tuberculosis, 2016 — Standard regimen and adverse effects
- WHO consolidated guidelines on tuberculosis: Module 4 Treatment and Module 1 Prevention, 2022 — Drug-susceptible TB treatment; tuberculosis preventive treatment
- Harrison's Principles of Internal Medicine, 21st edition (2022) — Tuberculosis
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.