Heaf test

From Wikipedia, the free encyclopedia

The Heaf test is a diagnostic skin test performed in order to determine whether or not a child has been exposed to tuberculosis. Patients who exhibit a negative reaction to the test may be offered BCG vaccination. The test is named after F. R. G. Heaf.

Until 2005, the test was used in the United Kingdom to determine if the BCG vaccine was needed; the Mantoux test is now used instead. The Heaf test was preferred in the UK, because it was felt that the Heaf test was easier to interpret, with less inter-observer variability, and that less training was required to administer and to read the test. The test was withdrawn because manufacturers could not be found for tuberculin or for Heaf guns.

The Heaf test may be informally referred to as the six pricks, as it gives six individual injections.

[edit] 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 (positive)
• Grade 3 - Central filling to form disc (positive)
• Grade 4 - Disc >10 mm with or without blistering (strongly positive)

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.

For interpretation of the test, see Tuberculosis diagnosis.

[edit] Other Tests

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)

The Mantoux test is preferred in the United States for the diagnosis of tuberculosis; multiple puncture tests, such as the Heaf test and Tine test, are not recommended.

[edit] 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. Table 3 Heaf Test grading, reaction, and equivalent Mantoux positive levels. PMID 11050256