Contents

Search

tuberculin-skin testing (TST)

Indications: - evaluation of exposure to tuberculosis Contraindications: - evaluation of reactivation of latent tuberculosis (obtain chest X-ray) * once positive, test remains positive after treatment for active tuberculosis or latent tuberculosis Procedure: - purified-protein derivative* is injected intradermally in the forearm - the site is inspected 48-72 hours later * .Purified-protein derivative is the antigen commonly used in tuberculin-skin testing. - a booster effect of a positive 2nd test a few weeks following a negative test may occur, most commonly in older patients with latent TB, atypical Mycobacterial infection & in persons who previously received BCG - discharge of an elderly patient to a skilled nursing facility after hospitalization requires a 2-step PPD, the 2nd PPD placed after 2 weeks [4] * CDC's Mantoux Tuberculin Skin Test Video [9] Interpretation: Criteria for a positive TST are: 1) 5-mm induration for a) patients with HIV infection or other immunodeficient condition* b) recent contacts with a known case of active TB c) patients with prior chest radiographs typical of TB d) immunosupression (equivalent of >= 15 mg of prednisone for 4 weeks) [2] 2) 10-mm induration for a) immigrants from high prevalence areas (Asia, Africa, Latin America, eastern Europe, Russia) b) prisoners & prison employees c) homeless & homeless shelter employees d) IV drug abusers [2,5] e) nursing home or long-term care residents & employees f) medically underserved, low income populations g) patients with chronic medical illnesses - diabetes mellitus - chronic renal disease - gastrectomy/achlorhydria - weight loss [4] h) hospital workers i) Mycobacteriology lab personnel j) children < 4 years of age or exposed to high-risk adults 3) 15-mm induration for individuals not in a high prevalence group * includes > 15 mg/day of prednisone for > 4 weeks [2] or other immunosuppressive therapy induration is measured, not the erythema [2] Sensivitity of tuberculin skin testing for latent TB is close to 100% [3] 20-25% of patients with active tuberculosis may have a negative skin test. [8] Test conversion among healthcare workers is unrelated to exposure to tuberculosis If controls are used with PPD, mumps is used as a positive control, Candida is used as a negative control. BCG vaccination should not affect interpretation of TST. BCG vaccination may cause false positive [2] Atypical Mycobacteria may cause false positives [2] ; * CDC's Mantoux Tuberculin Skin Test Video [9] Complications: - 5% of individuals with recent conversion of tuberculin skin testing (TST) will develop active disease within 1 year if left untreated - adequate treatment reduces this risk* * Contrary to popular belief, false positives occur, subjecting patients to unnecessary prolonged treatment with antibiotics - patients with false positive PPD may test negative on retesting Management: - rule out active TB, prior to treatment of latent TB - chest X-ray indicated for tuberculin-positive test - INH prophylaxis 300 mg PO QD for 6-12 months is recommended for: a) a positive TST conversion within 2 years regardless of age b) persons with a history of untreated TB or radiographic evidence of previous TB c) all TST-positive individuals < 35 years of age d) persons with a positive TST who are at high risk for TB e) new TST converters > 15 mm on serial testing f) household members & close contacts of patients with TB who have a positive TST - rifampin 600 mg PO QD for 6 months is an alternative to INH. - multidrug-resistant tuberculosis: - pyrazinamide & quinolone (ciprofloxacin) or ethambutol for 6 months - consider other Mycobacteria if evidence of infection but negative tuberculin skin testing Also see chemoprophylaxis for tuberculosis

Related

chemoprophylaxis for tuberculosis Mycobacterium tuberculosis (MTB) purified protein derivative (PPD, Tubersol) QuantiFERON-TB test; interferon gamma release assay (IGRA)

General

skin testing screening for tuberculosis

References

  1. Manual of Medical Therapeutics, 28th ed, Ewald & McKenzie (eds), Little, Brown & Co, Boston, 1995
  2. Medical Knowledge Self Assessment Program (MKSAP) 11, 14, 15, 16, 17. American College of Physicians, Philadelphia 1998, 2006, 2009, 2012, 2015 - Medical Knowledge Self Assessment Program (MKSAP) 19 Board Basics. An Enhancement to MKSAP19. American College of Physicians, Philadelphia 2022
  3. American Thoracic Society Targeted Tuberculin Testing and Treatment of Latent Tuberculosis Infection http://www.thoracic.org/sections/publications/statements/pages/mtpi/latenttb1-27.html
  4. Geriatric Review Syllabus, 7th edition Parada JT et al (eds) American Geriatrics Society, 2010 - Geriatric Review Syllabus, 11th edition (GRS11) Harper GM, Lyons WL, Potter JF (eds) American Geriatrics Society, 2022
  5. Centers for Disease Control and Prevention Targeted tuberculin testing and treatment of latent tuberculosis infection. American Thoracic Society. MMWR Recomm Rep. 2000 Jun 9;49(RR-6):1-51. PMID: 10881762
  6. Centers for Disease Control and Prevention National Shortage of Purified-Protein Derivative Tuberculin Products. MMWR. April 26, 20013 http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6216a5.htm
  7. Dorman SE et al. Interferon-gamma release assays and tuberculin skin testing for diagnosis of latent tuberculosis infection in healthcare workers in the United States. Am J Respir Crit Care Med 2014 Jan 1; 189:77 PMID: 24299555
  8. Dagogo-Jack I, Vaidya A, Geller B, Baden LR, Stone R. A Man with Fever, Cough and Rash N Engl J Med 2014 371:e11. August 21, 2014 PMID: 25140977 http://www.nejm.org/doi/full/10.1056/NEJMimc1310796
  9. Centers for Disease Control and Prevention Mantoux Tuberculin Skin Test Video https://www.youtube.com/watch?v=Qzt-qGgglo0
  10. Centers for Disease Control and Prevention Fact Sheets. Tuberculin Skin Testing https://www.cdc.gov/tb/publications/factsheets/testing/skintesting.htm