Do I need a Mantoux test for tuberculosis screening?

Do You Need a Mantoux Test for TB Screening?

Whether you need a Mantoux tuberculin skin test (TST) depends on your specific risk factors—you should receive testing if you have HIV infection, recent TB exposure, injection drug use history, homelessness, incarceration history, or belong to other high-risk populations. 1

High-Priority Indications for Mantoux Testing

Immediate Testing Required

• HIV-infected persons: All individuals should receive a TST as soon as possible after HIV diagnosis unless previously documented as TST-positive 1
• Recent TB exposure: Anyone exposed to infectious pulmonary or laryngeal TB should be tested as soon as possible (ideally within 7 days), regardless of previous TST results 1
• Healthcare workers: All personnel at employment should receive baseline Mantoux testing unless they have documented previous positive reaction or completed adequate therapy 1

Standard Risk-Based Screening Populations

You should receive Mantoux testing if you have any of the following: 1, 2

• History of injection drug use
• Current or recent homelessness
• Current or recent incarceration
• Contact with a person with pulmonary TB
• Immigration from high TB prevalence countries
• Residence in congregate settings (prisons, jails, homeless shelters, nursing homes, mental institutions) 1
• Medical conditions increasing TB risk: silicosis, diabetes mellitus, chronic corticosteroid therapy, immunosuppressive therapy, end-stage renal disease, hematologic malignancies, substantial weight loss, chronic malabsorption 2

Interpretation Thresholds

The size of induration that defines a positive test varies by risk level: 3, 2

• ≥5 mm induration: HIV-infected persons, recent TB contacts, persons with fibrotic chest radiograph changes, immunosuppressed patients 1, 2
• ≥10 mm induration: Foreign-born persons from high-prevalence countries, injection drug users, residents of high-risk congregate settings, healthcare workers, persons with high-risk medical conditions, children <4 years old 1, 3, 2
• ≥15 mm induration: Persons with no known TB risk factors 1, 3

Special Considerations

BCG Vaccination History

Prior BCG vaccination should NOT prevent you from receiving or interpreting a Mantoux test—positive reactions in BCG-vaccinated persons from high-prevalence areas usually indicate true M. tuberculosis infection and should be evaluated for preventive therapy 1, 3, 4. However, for patients ≥5 years old with prior BCG exposure, an interferon-gamma release assay (IGRA) is preferred over TST due to superior specificity 3.

Healthcare Worker Periodic Screening

If you work in healthcare, the frequency of repeat testing depends on your exposure risk: 1

• Workers frequently exposed to TB patients or performing high-risk procedures (bronchoscopy, sputum induction, aerosol treatments): retesting at least every 6 months 1
• Other healthcare personnel: annual retesting 1
• After unprotected exposure: immediate testing and repeat at 12 weeks if initially negative 1

When NOT to Test

You do NOT need routine Mantoux testing if: 1, 5

• You have documented previous positive TST or completed adequate therapy for TB disease or latent infection 1
• You are a child whose only risk factor is living in an urban area with low TB prevalence—annual screening is not warranted in this population 5
• You have no risk factors and are ≥35 years old (unless induration ≥15 mm, though benefit must be weighed against hepatitis risk from preventive therapy) 2

Critical Testing Technique

The Mantoux test must be performed correctly to be valid: 4

• Use 0.1 mL of 5-TU purified protein derivative (PPD) administered intradermally 1, 4
• A visible "wheal" must be produced; if significant leakage occurs or injection is subcutaneous, repeat immediately at another site 4
• Read at 48-72 hours by measuring induration (not erythema) by palpation 3, 4
• If only erythema >10 mm without induration is present, the injection was likely too deep and retesting is indicated 4

Common Pitfall

The Mantoux test is sensitive but not specific—86% of patients with active TB have positive tests, but 42% of positive tests occur in persons without active disease (often representing past infection) 6. Therefore, all positive tests require chest radiography and clinical evaluation to distinguish latent infection from active disease before initiating preventive therapy 1.