Editing Heaf test (section)

==Procedure==
A '''Heaf gun''' was used to inject multiple samples of testing serum under the skin at once. The needle points were dipped in tuberculin purified protein derivative (PPD) and pricked into the skin.<ref>{{Cite web|url=http://www.credoreference.com/entry.do?id=3163273|title=Sterneedle test|year=1992|work=Academic Press Dictionary of Science and Technology|publisher=[[Elsevier#Science &Technology|Elsevier Science & Technology]]|location=Oxford|accessdate=17 October 2010}} {{subscription required}}</ref>
A Heaf gun with disposable single-use heads was recommended.

The gun injected PPD 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 was read between two and seven days later. The injection could not be into sites containing superficial veins.

The reading of the Heaf test was defined by a scale:<ref>{{Cite journal|last1=Galbraith|first1=N. S.|last2=Hanson|first2=Audrey|last3=Shoulman|first3=R.|last4=Andrews|first4=D. W.|last5=Lee|first5=D. B.|date=1972|title=Interpretation Of Positive Reactions To Heaf Tuberculin Test In London Schoolchildren|journal=The British Medical Journal|volume=1|issue=5801|pages=647–649|doi=10.1136/bmj.1.5801.647|jstor=25417979|pmid=4622617|pmc=1787811|issn=0007-1447}}</ref>
* Negative – no induration, maybe six minute puncture scars
* Grade 1 – four to six [[papules]] (also considered negative)
* Grade 2 – confluent papules form indurated ring (positive)
* Grade 3 – central filling to form disc (positive)
* Grade 4 – disc >10&nbsp;mm with or without blistering (strongly positive)

Grades 1 and 2 could result from previous BCG or avian tuberculosis, rather than human TB infection.

Children who were found to have a grade 3 or 4 reaction were referred for [[X-ray]] and follow-up.

For interpretation of the test, see [[Tuberculosis diagnosis]].