A nurse is checking the forearm of a client who received a tuberculin skin test 48 hr ago. Which of the following findings at the injection site should indicate to the nurse a positive result?

A. Excoriation. Excoriation (skin abrasion or scratching) does not indicate a positive tuberculin skin test. A positive reaction is determined by induration (firm swelling) rather than skin irritation or superficial damage. Scratching the site can cause redness, but this is not a diagnostic sign of tuberculosis exposure. B. Firmness. A positive tuberculin skin test is identified by the presence of induration (firm, raised swelling) at the injection site, which is measured in millimeters. The size of induration considered positive depends on the client’s risk factors. For example, ≥5 mm is positive in immunocompromised individuals, ≥10 mm in high-risk populations, and ≥15 mm in individuals with no risk factors. C. Ulceration. Ulceration is not a typical reaction to a tuberculin skin test. If ulceration occurs, it may indicate improper injection technique, irritation, or an allergic reaction, rather than a true positive result. The test should be repeated in such cases. D. Bleeding. Minor pinpoint bleeding at the injection site may occur due to the needle puncture but does not indicate a positive result. The key indicator of a positive test is the presence of measurable induration, not redness, bruising, or bleeding.