The purified protein derivative test, also called a PPD, is a screening test for exposure to tuberculosis. Your physician may order this test if you have recently been overseas, live in a community with a high incidence of TB, or have recently been exposed to TB. A positive test reaction is not diagnostic for active TB but requires further follow-up testing. There are few side effects to the PPD test, but notify your physician if they persist.
Itching
The PPD test requires a tiny injection just under the tissue usually in the forearm below the elbow. The injection raises a small mark resembling a blister. You may experience itching at the injection site and it is a common reaction to the PPD test. Do not scratch or rub the area, as it may squeeze the testing fluid out of the site, requiring a repeat test, according to Drugs.com.
Redness
You may notice redness, called erythema, at the PPD test site, but it does not have diagnostic value for TB, according to the DailyMed. Only a palpable induration, defined as a hard, raised area with a definite border, is considered diagnostic for a positive test result. Your physician or the nurse measures the size of the raised area after palpating the area with fingertips. A hard, raised area greater than or equal to 10 mm might require follow-up testing.
Pain
Pain at the injection site for a PPD is not uncommon and usually transient. It may be a result of your individual reaction to a needle stick and the pressure of the test fluid temporarily displacing tissue. If your pain continues, worsens or causes concern, notify your physician for medical treatment as recommended by the Mayo Clinic.
Edema
Swelling, or edema, at the site of a PPD is also considered a common side effect and should disappear within a short time. This type of swelling is not the same as the raised area associated with a positive skin reaction. Your forearm may feel swollen to the touch but without an area that is hard and raised.
Member Comments