It is currently recommended that an induration of ≥ 5 mm is significant and be read as positive if the child is HIV-infected or severely malnourished. Skin testing should be performed by intradermal injection (Mantoux method) of 5 tuberculin units of purified protein derivative of tuberculin (PPD) per 0.1 mL, usually into the skin of the volar surface of the forearm. A positive or reactive TST indicates TB infection and is defined as ≥ 10 mm diameter of induration when read 48–72 hours after administration in any child irrespective of BCG immunization.13 There is a large amount of data to support this cut-off. the child with HIV infection or severe malnutrition. A positive Mantoux tuberculin skin test or interferon gamma release assay (IGRA) test result means that the person is likely to have been exposed to tuberculosis and the person may have a latent or active tuberculosis infection. The recommended method is the Mantoux test using either 5 tuberculin units of tuberculin purified protein derivative (PPD) or 2 tuberculin units of PPD RT23. The TST is a test of delayed-type, cell-mediated hypersensitivity to purified protein derivative.

Some of the other causes of false-negative TST are listed in Table 16.2. Routine neonatal BCG vaccination has little impact on the size of the TST reaction in adults; however, it may be a confounding factor in people revaccinated at school age or adolescence.42,43 Recent knowledge about the important role of T lymphocytes and interferon-γ (IFN-γ) in tuberculosis has led to the development of in vitro diagnostic tests known as interferon-γ release assays (IGRA) to detect tuberculous infection. H Simon Schaaf, Helmuth Reuter, in Tuberculosis, 2009.

The results are read in 48-72 hours for induration(elevated hardened area). J.R. Starke, in Encyclopedia of the Neurological Sciences (Second Edition), 2014. The potential problem of poor specificity (often false-positive) due to BCG immunization or infection with environmental (non-tuberculous) mycobacteria is often mentioned.

By continuing you agree to the use of cookies. The test should be read as the number of millimeters of palpable induration present after 48–72 hours. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. URL: https://www.sciencedirect.com/science/article/pii/B9781416039884000299, URL: https://www.sciencedirect.com/science/article/pii/B9781416039884000512, URL: https://www.sciencedirect.com/science/article/pii/B9780702039355000355, URL: https://www.sciencedirect.com/science/article/pii/B9780323040488500438, URL: https://www.sciencedirect.com/science/article/pii/B9781416039884000160, URL: https://www.sciencedirect.com/science/article/pii/B9780123851574003663, URL: https://www.sciencedirect.com/science/article/pii/B9781455707928000313, URL: https://www.sciencedirect.com/science/article/pii/B9781416039884000226, URL: https://www.sciencedirect.com/science/article/pii/B9781455748013000163, Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases (Eighth Edition), 2015, Christopher J Hoffmann, Gavin J Churchyard, in, Clinical aspects of tuberculosis in HIV-infected adults, The criterion for a positive tuberculin skin test is lower in HIV infection (≥ 5 mm induration on the, Tuberculosis and Atypical Mycobacterial Infections, Edward C. Jones-Lopez, Jerrold J. Ellner, in, Tropical Infectious Diseases (Third Edition), Pediatric Respiratory Medicine (Second Edition), Clinical features and index of suspicion of tuberculosis in children, The TST provides important additional information in the assessment of the child with suspected TB.
Reactions of various sizes may occur, but the larger the reaction, the more likely it is caused by infection with M. tuberculosis.

These assays offer the advantages that they can be done in a single visit, there is little interobserver variability, and there are no boosted responses.

Positive TST skin reactions due to BCG vaccination wane with time. Up to 10% of otherwise normal children with culture-proved TB do not react to tuberculin initially.81 Most of these children will become reactive during treatment, suggesting that TB disease may itself contribute to immunosuppression.

However, IGRAs have several important limitations:44 (1) they have not been sufficiently validated in large prospective studies for reliability over time (stability); (2), as with the TST, IGRAs do not reliably distinguish LTBI from active TB disease; (3) a growing number of studies, particularly among HIV-infected subjects and household contacts of infectious TB cases, show discordance between IGRA and TST results in individuals likely to be M. tuberculosis infected; (4) their performance in programmatic conditions in high TB prevalence countries45 is not well validated.

A positive tuberculin skin test (TST) only indicates infection with M. tuberculosis, and does not indicate immunity to TB, the time of infection, or the presence or extent of disease. Experts agree that a skin test interpretation for a patient who received a BCG vaccine more than 3 years previously should be the same as if they had never received the vaccine. Nevertheless, especially in children, TST is a useful adjunct in diagnosing TB, when it is used in conjunction with clinical examinations and other diagnostic tests. The tuberculin skin test is the traditional method for assessing exposure to M. tuberculosis. The operating characteristics of the test are dependent on the population tested, the amount of nonspecific cross-reactions (generally small reactions) due to prior BCG vaccination or infection with environmental mycobacteria, and the cut point used. In HIV-infected patients the tuberculin skin test is more likely to be negative as the CD4+ lymphocyte count declines.33 The criterion for a positive tuberculin skin test is lower in HIV infection (≥ 5 mm induration on the Mantoux test), although this has recently been challenged.34 Although false-negative tuberculin skin tests occur more often in HIV-infected patients, particularly in the significantly immune-suppressed, meta-analysis shows that TB preventive therapy is only effective if the skin test is positive.35.

Mantoux tuberculin skin test 1 Administration 2 Reading 3 Interpretation 5 Record measurement of induration in mm If no induration, record as 0 mm Do not record as “positive” or “negative” Only record measurement in mm 5 Record information Record all the information required for documentation by your TST is widely used in epidemiologic surveys to assess the prevalence and estimate the annual rate of TB infection and in clinical practice to assess whether a person has been infected with M. tuberculosis and has latent TB infection (LTBI). bCG (bacille Calmette-Guerin) vaccination may transiently cause a reactive TST, but most children who received bCG as infants have a nonreactive TST at 5 years of age.88 A recent meta-analysis suggests that the effect of bCG on TST measurements was less after 15 years, and induration greater than 15 mm was more likely to be due to TB infection than bCG.89 Among older children or adolescents who receive bCG, most develop a reactive TST initially; however, by 10 to 15 years postvaccination, the majority will have lost tuberculin reactivity.90 Recent studies have shown that bCG vaccination had little impact on the interpretation of TST in children being tested as part of a contact investigation.91 There have been concerns that false-positive TST may arise through antigenic cross-reactivity from asymptomatic infection by environmental nontuberculous mycobacteria.92 Skin reactivity can also be boosted, probably through antigenic stimulation, by serial testing with TST in many children and adults who received bCG.93, Stephen M Graham, ... Robert P Gie, in Tuberculosis, 2009. Jean B Nachega, Gary Maartens, in Tuberculosis, 2009, The tuberculin skin test is the standard method of establishing the presence of latent TB infection.
Interpretation of TST results differs around the world and is summarized in Table 39-3. Delane Shingadia, David Burgner, in Pediatric Respiratory Medicine (Second Edition), 2008, A positive TST reaction is a hallmark of primary infection with MTB. The multiple-puncture tests, such as the Heaf test, Tine test, and Monotest, are not as reliable as the Mantoux test. A positive Mantoux test doesn't always mean someone has TB disease; it just means that the bacteria have been in the body at some time. Up to one-fourth of newly diagnosed patients with active pulmonary TB have negative tuberculin reactions.

Patrick R. Murray, in Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases (Eighth Edition), 2015. The TST provides important additional information in the assessment of the child with suspected TB. Sometimes it is useful to repeat the TST in children once their nutrition has improved or their severe illness (including TB) has resolved, as they may be initially TST negative, but positive after 1–3 months on treatment.

Erythema (redness) is not significant. A recent report indicates that, unlike the tuberculin skin test, these assays are less affected by HIV status.36 However, it remains to be seen whether these new assays predict the risk of TB better than the tuberculin skin test, and thus could replace it as an indication for treatment of latent TB infection. Over the past 3–5 years, IGRAs have gained widespread use in clinical settings and are increasingly used interchangeably with the TST to evaluate for M. tuberculosis infection. The main limitation of the TST is that it has a low sensitivity (often false-negative), especially in children in whom the diagnosis of TB is already the most difficult, i.e. Previous inoculation with Bacillus Calmette–Guérin (BCG) vaccine, the antituberculosis vaccine used throughout most of the world, can pose problems with the interpretation of a subsequent tuberculin skin test. In general, the sensitivity of the TST for detection of active TB ranges from 65% to 94%, but in critically ill patients with disseminated disease, the sensitivity decreases to only 50%.

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