Heaf test
From Free net encyclopedia
The Heaf test is a diagnostic skin test performed in order to determine whether or not a child has been exposed to tuberculosis.
It is used in the United Kingdom to determine if the BCG vaccine is needed. Patients who exhibit a negative reaction may be offered BCG vaccination.
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Procedure
A Heaf gun is used to inject multiple samples of testing serum under the skin at once. A Heaf gun with disposable single-use heads is recommended.
The gun injects purified protein derivative equivalent to 100,000 units per ml to the skin over the flexor surface of the left forearm in a circular pattern of six. The test is read between 2 and 7 days later. The injection must not be into sites containing superficial veins.
The reading of the Heaf test is defined by a scale:
- Negative - No induration, maybe 6 minute puncture scars
- Grade 1 - 4-6 papules (also considered negative)
- Grade 2 - Confluent papules form indurated ring
- Grade 3 - Central filling to form disc
- Grade 4 - Disc >10 mm with or without blistering
Grades 1 and 2 may be the result of previous BCG or avian tuberculosis.
Children who have a grade 3 or 4 reaction require X-ray and follow-up.
Other Tests
The equivalent Mantoux test positive levels done with 10 TU (0.1 ml 100 TU/ml, 1:1000) are
- 0-4mm induration (Heaf 0-1)
- 5-14mm induration (Heaf 2)
- >15mm induration (Heaf 3-4)
The Mantoux test is preferred in the United States for the diagnosis of tuberculosis; multiple puncture tests, such as the Heaf Test, are not recommended.
See also
References
- Joint Tuberculosis Committee of the British Thoracic Society, Control and prevention of tuberculosis in the United Kingdom: Code of Practice 2000 BMJ 2000:55:887-901. fulltext - Table 3 Heaf Test grading, reaction, and equivalent Mantoux positive levels. PMID 11050256
- The Heaf Test from Bignell Surgical Instruments Ltd, manufacturer of a Heaf Test gun. Includes Reading the Test with pictures of the different Grades and reactions.