A nurse is assisting with care for a client who received a tuberculin skin test 72 hr ago. When collecting data from the test site, which of the following findings indicates a need for further testing?
A.
Nonpalpable area of redness, less than 5 mm (0.2 in) in diameter
B.
Area of ecchymosis, greater than 12 mm (0.5 in) in diameter
C.
Tenderness at the injection site
D.
Palpable area of induration, greater than 10 mm (0.4 in) in diameter
The correct answer and Explanation is :
The correct answer is D. Palpable area of induration, greater than 10 mm (0.4 in) in diameter.
Explanation:
The tuberculin skin test (TST), also known as the Mantoux test, is used to determine if a person has been exposed to the tuberculosis (TB) bacteria. After the intradermal injection of tuberculin, the reaction is assessed 48 to 72 hours later. The key findings to evaluate include induration (a raised, hardened area), redness, and any other reactions at the injection site.
Understanding the Responses:
- A. Nonpalpable area of redness, less than 5 mm (0.2 in) in diameter: This finding typically indicates a negative test. Redness without induration does not signify TB infection.
- B. Area of ecchymosis, greater than 12 mm (0.5 in) in diameter: Ecchymosis (bruising) is not a part of the typical TST reaction and suggests trauma or improper injection rather than a positive result for TB.
- C. Tenderness at the injection site: While tenderness can occur, it does not necessarily indicate a positive test. Tenderness alone does not provide enough information regarding TB exposure.
- D. Palpable area of induration, greater than 10 mm (0.4 in) in diameter: This is the critical finding. An induration of greater than 10 mm is considered significant in individuals who are at moderate risk for TB, such as those with certain medical conditions or those who are immunocompromised. A palpable area of induration indicates that the immune system has responded to the tuberculin, suggesting possible exposure to TB and necessitating further testing, such as a chest X-ray or additional diagnostic assessments.
In summary, the presence of induration greater than 10 mm is a definitive indicator that further evaluation for TB infection is warranted, making option D the correct choice.