Interpretation of the tuberculin skin test reaction by pediatric providers

The tuberculin (TB) skin test is widely used, but it is not easy to read. There are few data on how well pediatric care providers interpret the TB skin test or on the success of various methods used to read the skin test reaction.

To determine the ability of pediatric care providers to correctly read a positive TB skin test reaction and to identify the most successful method of measuring a TB skin test reaction.

Twenty nurses, 16 staff pediatricians, 13 residents and 8 medical students who were working in a large pediatrics clinic were asked to read a 15-mm TB skin test reaction of a known converter. The study participants read the skin test using any technique they wished. The primary outcome measure was the percentage of providers who read the TB skin test as > or = 10 mm (considered a correct reading).

Seventy-seven percent (44 of 57) of the participants interpreted the TB skin test as > or = 10 mm, but 18% (10 of 57) of them read the skin test as negative (< or = 5 mm). The participants used a variety of interpretation techniques with 18 using the ballpoint pen technique. Participants who used the pen technique were significantly more likely to read the skin test as > or = 10 mm compared with those who used other methods (94% vs. 69%; P = 0.04). Pen technique users were also significantly less likely to measure the reaction as < or = 5 mm (0% vs. 26%; P = 0.02).

Many providers, regardless of professional training and experience, read a 15-mm TB skin test reaction as > or = 10 mm, but a significant minority interpreted it as negative. Use of the pen technique may decrease the number of false negative readings. Specific instruction on use of the pen technique to read TB skin tests should be incorporated into medical training curriculums.