Heaf test
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 done in the United Kingdom to determine if the BCG vaccine is needed. Patients who exhibit a negative reaction may be offered BCG vaccination.
Multiple puncture tests such as the Heaf Test are not recommended for the diagnosis of tuberculosis in the United States. Instead, the Mantoux test is preferred.
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.
The equivalent Mantoux test positive levels done with 10 TU (0.1 ml 100 TU/ml, 1:1000) are
- 0-4 mm induration (Heaf 0-1)
- 5-14 mm induration (Heaf 2)
- >15 mm induration (Heaf 3-4)
See also
