Influence of needle gauge in Mantoux skin testing.

STUDY OBJECTIVE To determine the influence of needle gauge in Mantoux skin testing for tuberculosis. DESIGN Randomized selection of either a 27- or 30-gauge needle for Mantoux skin test placement; observer-blinded. SETTING Annual hospital employee screening. PARTICIPANTS Six hundred twenty-five employees working in clinical and laboratory research environments. RESULTS Blinded observers found that the use of 27-gauge needles caused increased bleeding and bruising compared with 30-gauge needles (p < or = 0.007 for each). However, the 27-gauge needle produced larger blebs and less leakage of tuberculin solution (p < or = 0.0003). CONCLUSION Smaller gauge needles could potentially cause false-negative screening results because of decreased antigen delivery. Use of needle gauges smaller than 27 gauge should be avoided until their reliability is validated.