Pediatric TB: TST vs IGRA, Latent TB Treatment (3HP, 4R) and Next Steps

About this tool

This tool guides a clinician through tuberculosis in a child, starting with why TB is being considered: risk screening, contact with a person with active TB, a positive TB test, or symptoms and an abnormal chest X-ray.

For screening it applies the risk questions and chooses the test: IGRA is preferred from 2 years of age and the TST for younger children, with TST cutoffs of 5, 10 or 15 mm by risk group. BCG does not change the interpretation. For contacts it covers window prophylaxis for children under 5 years and immunocompromised children with a negative first test, with a repeat test 8–10 weeks after the last contact.

For latent TB infection it shows the CDC/NTCA 2020 regimens with pediatric doses: 3HP weekly for 12 weeks from 2 years, 4 months of rifampin, 3 months of isoniazid plus rifampin, or 6–9 months of isoniazid, with pyridoxine indications. Possible TB disease leads to referral to a TB specialist and the health department, specimen collection, and isolation advice.

Common questions

Should I use a TST or an IGRA in children?

From 2 years of age an IGRA is preferred, especially after BCG vaccination; a TST is acceptable. Under 2 years the TST is preferred. Neither test can rule out TB disease.

Does BCG vaccination change how a TST is read?

No. The Red Book advises reading the TST with the usual 5, 10 and 15 mm cutoffs regardless of BCG history. IGRA is not affected by BCG and is preferred in BCG-vaccinated children 2 years and older.

What is window prophylaxis?

Treatment given to a child under 5 years (or immunocompromised) exposed to TB whose first test is negative and chest X-ray normal. The test is repeated 8–10 weeks after the last contact; if still negative in a healthy child, treatment stops.

Which latent TB regimen is preferred for children?

Short rifamycin regimens: 3HP (weekly isoniazid plus rifapentine for 12 weeks, 2 years and older), 4 months of daily rifampin, or 3 months of daily isoniazid plus rifampin. Isoniazid for 6–9 months is an alternative.

Is a child with TB disease contagious?

Young children usually are not, because they have few bacteria and a weak cough. Adolescents with cavities or positive sputum smears can be. Adult visitors should be checked, since they are often the source.

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