Not just color: The test is usually read at 48 or 72 hour after it is applied to the forearm. A measurement of the area of redness, if any, and or the area of thickened skin, is then taken. The size of the thickened area (diameter) will lead to the decision on whether it is positive or not. Various patient specific issues are factored into the decision.
Answered 5/21/2013
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A doctor has provided 1 answer
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