Related Experiment Videos
Tuberculin test
1National Tuberculosis Institute, Bangalore, India. ntiindia@blr.net.in
Insights
The standard tuberculin test helps detect tuberculosis infection in children. Larger induration sizes (≥15 mm) strongly suggest infection, while smaller sizes (<10 mm) are less indicative.
Area of Science:
- Pediatrics
- Infectious Diseases
- Immunology
Background:
- The tuberculin test is a common tool for diagnosing tuberculous infection in children.
- Clear guidelines for its performance and interpretation are often lacking.
- Understanding test results is crucial for accurate diagnosis and management.
Purpose of the Study:
- To clarify the performance and interpretation of the standard tuberculin test.
- To provide evidence-based guidance for healthcare professionals.
- To improve the diagnostic accuracy of tuberculosis detection in pediatric populations.
Main Methods:
- Intradermal injection of 1TU PPD RT23 with Tween 80.
- Measurement of the maximum transverse diameter of induration after 72 hours.
- Analysis of induration size in relation to tuberculous infection probability and influencing factors.
Main Results:
- Indurations of 15 mm or larger strongly indicate tuberculous infection, regardless of BCG vaccination status.
- Indurations <5 mm suggest no tuberculin sensitivity; 5-9 mm are typically non-tuberculous.
- Indurations of 10-14 mm require careful interpretation, considering contact history and clinical signs.
Conclusions:
- The size of induration is a key indicator of tuberculous infection.
- Contextual factors like contact history and clinical presentation are vital for interpreting intermediate results.
- Immuno-suppressive conditions can affect induration size, necessitating comprehensive evaluation.
Abstract:
Although tuberculin test is widely used for detection of tuberculous infection among children, there is no clear understanding about its performance and interpretation. This article has been written with the purpose of elucidating the performance and interpretation of standard tuberculin test, based on the experiences gained at the National Tuberculosis Institute, Bangalore and other centres. The standard tuberculin test involves intradermal injection of '1TU PPD RT23 with Tween 80' on the mid-volar aspect of forearm and measurement of the maximum transverse diameter of induration after 3 days. Larger the size of induration, higher is the probability of it being due to tuberculous infection. The majority of reactions with induration size of 15 mm and above are attributable to infection with tubercle bacilli, irrespective of BCG-vaccination status. While indurations of less than 5 mm indicate absence of any kind of tuberculin sensitivity, the majority of indurations in 5-9 mm range are usually of non-tuberculous nature. An induration of 10-14 mm requires more careful interpretation. It is more likely to be attributable to infection with tubercle bacilli in case of history of contact with smear positive case or among children with clinical findings of tuberculosis. However, the size of induration in an infected child may be diminished in the presence of immuno-suppressive conditions. One should also consider the purpose of the test while interpreting the test results.