Tuberculosis resident survival guide
|Tuberculosis Resident Survival Guide Microchapters|
Synonyms and Keywords: Approach to tuberculosis, Approach to TB, Tuberculosis workup, TB workup
Tuberculosis (TB) is a common and very contagious infectious disease caused by Mycobacterium tuberculosis bacteria (MTB). MTB can affect every system of the human body, but most commonly affects the respiratory system since this organism grow vigorously in high oxygen environments. It is calculated that more than a third of the world's population has been exposed to MTB, being the vast majority of them asymptomatic and maintaining as latent. Symptoms of respiratory active tuberculosis includes hemoptysis, shortness of breath, fever, chills, night sweats, and weight loss. Usually latent tuberculosis is treated with a regimen of 6-9 months of rifampin or isoniazid, while active TB is managed with a phase of four antituberculous agents (rifampin, isoniazid, ethambutol, pyrazinamide) for 2 months to later be continued only by isoniazid and rifampin 4 more months.
Test for latent tuberculosis
- Tuberculin skin test. Also known as Mantoux test or PPD consists in the visualization of the skin reaction after the injection of M. tuberculosis antigens 24, 48, and 72 hours after. A positive result is interpreted as the following:
- QuantiFERON-TB. Detects cell-mediated immunity to tuberculin.
- QuantiFERON-TB Gold. Detects IFN-g released by sensitized T cells by M. tuberculosis antigens in vitro.
- T SPOT-TB. Detects T cells stimulated by M. tuberculosis.
- AMPLICOR assay. Uses DNA polymerase chain reaction (PCR) to amplify nucleic acid targets.
Tests for active tuberculosis disease
- Microbiological detection:
- Acid fast bacilli stain. This tests is relatively fast and cheap but presents with a high number of false positives, since may detect Mycobacterium bovis or NBT.
- Mycobacterial culture. This test is cheap but takes weeks to have results. Culture may be done in 3 types of media: solid media (Lowenstein Jensen), agar-based media (Middlebrook 7H10 and 7H11), and liquid media (Middlebrook 7H12).
- Nucleic acid amplification assays. This test is rapid and specific to M. tuberculosis but costly and gives no drug susceptibility.
- Response to therapy. Clinical response to antituberculous drugs may be an indicator of TB infection, but lead time bias should assesed.
- Tuberculosis infection is caused by mycobacterium tuberculosis which is transmitted from person to person by inhalation of aerosols from an affected individual with active TB.
- Tuberculosis may be spread through cough, sneezing, singing, spitting, or even talking because these particles may remain suspended in the air for several hours.
Shown below is an algorithm summarizing the diagnosis of Tuberculosis according the the Association of Chest Physicians guidelines:
|Sputum examination + Chest X-ray|
|Sputum positive for TB, Chest X-ray suggestive of TB||Sputum positive for TB, chest X-ray not suggestive of TB||Sputum negative for TB, chest X-ray suggestive of TB||Sputum negative for TB, chest X-ray not suggestive of TB||High clinical suspicion for TB|
|Cartridge-Based Nucleic Acid Amplification Test|
|Mycobacterium tuberculosis detected||Mycobacterium tuberculosis not detected or Cartridge-Based Nucleic Acid Amplification Test result not available||Considere alternate diagnosis|
|Rifampicin sensitive||Rifampicin indeterminate||Rifampicin resistant||Clinically diagnosed TB||Alternate diagnosis|
|Microbiologically confirmed TB||Repeat Cartridge-Based Nucleic Acid Amplification Test on 2nd sample||Refer to management of Rifampicin resistance|
|Indeterminate of 2nd sample, collect fresh sample of liquid culture/ Line Probe Assay|
|Place patient on RIPE (rifampin, isoniazide, pyrazinamide, ethambutol)|
|Did the specimen sent for culture at the initial evaluation return positive?|
|Give isoniazide and rifampin for 4 months|
|Was there cavitation on initial chest X-ray?||No||Is the patient HIV positive?||No|
|Yes||Yes||Give isoniazide and rifampin for 4 months|
|Give isoniazide and rifampin for 7 months|
- Suspect TB in individuals with:
- For long use of isoniazide, such as the management of TB always use pyridoxine (vitamin B6) to prevent peripheral neuropathy.
- Be aware of drug interactions between rifampin and antivirals in patients with HIV.
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- Pahal P, Sharma S. PMID 32310497 Check
|pmid=value (help). Missing or empty
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- Pourakbari B, Mamishi S, Benvari S, Mahmoudi S (September 2019). "Comparison of the QuantiFERON-TB Gold Plus and QuantiFERON-TB Gold In-Tube interferon-γ release assays: A systematic review and meta-analysis". Adv Med Sci. 64 (2): 437–443. doi:10.1016/j.advms.2019.09.001. PMID 31586819.
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- Zhu F, Ou Q, Zheng J (January 2018). "Application Values of T-SPOT.TB in Clinical Rapid Diagnosis of Tuberculosis". Iran. J. Public Health. 47 (1): 18–23. PMC 5756596. PMID 29318113.
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- "tb_therapeutic_tables [TUSOM | Pharmwiki]".