My facility requires tuberculosis (TB) skin testing for all staff and volunteers. When the practitioner injected a dose of tuberculin purified protein derivative (PPD) into my forearm, no bleb or wheal appeared. When I questioned her, she said she doesn't always see wheals now that she's using TB safety syringes. This surprised me because I'd been taught that I.M. injection of PPD, if performed correctly, will raise a wheal. Has the advent of safety equipment changed the procedure?-C.A., CALIF.
No. According to current best-practice guidelines issued by the CDC, the Mantoux tuberculin skin test (TST) is performed by injecting 0.1 mL of PPD intradermally into the inner surface of the forearm with a tuberculin syringe. This should produce a "pale elevation of the skin (a wheal) 6 to 10 mm in diameter." Using TB safety syringes, which are widely available, doesn't alter this procedure or the result.
Chances are the injection you received was mistakenly administered into subcutaneous tissue. Sounds like the staff member who administered it needs more training. Alert your facility's infection control practitioner so she can trigger staff education sessions ASAP.
Source: Centers for Disease Control and Prevention, Tuberculin skin testing, http://www.cdc.gov/tb/pubs/tbfactsheets/skintesting.htm.