How To Read A Ppd Skin Test

When a PPD test is Read that means it is looked to to determine the amount of swelling that was caused by the injection. You are not looking for redness or bruising, you are looking for an area that is raised or slightly swollen and referred to as the induration, a fancy word for localized swelling. A positive or negative reading is determined by the size of the induration along with other factors such as the person's immune system status or other diseases such as Diabetes, Crohn's or kidney disease.

The PPD skin test for tuberculosis is interpreted based on the diameter of the swelling around the skin pricks. A diameter equal to or greater than 15 mm in an otherwise healthy person is considered a positive result.