UNDERREADING OF THE TUBERCULIN SKIN-TEST REACTION

Study objective: The tuberculin skin test is the best diagnostic metho d to detect tuberculous infection. How accurate is interpretation of t he test? Design: Observational study. Setting: Both general hospital a nd university hospital. Participants: One hundred seven health-care pr ofessionals, including 52 practicing pediatricians, 33 pediatric house officers, 10 pediatric academicians, 11 registered nurses, and I pedi atric nurse practitioner. Study: A tuberculin skin test (Mantoux) was applied to the arm of a known tuberculin converter. As participants en tered/left the room, they were guided to the tuberculin converter. At no time did a participant observe-readings other than his/her own. Res ults: Mantoux tuberculin reaction measuring 15 mm induration was read individually by a group of 52 practicing pediatricians, 33 pediatric h ouse officers, 10 pediatric academicians, 11 registered nurses, and on e pediatric nurse practitioner. The median induration recorded by this group of 107 health-care professionals was 10 mm, and 17 (33%) practi cing pediatricians read the reaction as <10 mm induration. Using the g reater than or equal to 15-mm induration indicator to identify a posit ive reaction, 93% of those in the study (99/107 participants) would ha ve identified our known converter as tuberculin negative. Conclusion: This study confirms a general inaccuracy in interpretation of the tube rculin skin test reaction, It raises two questions. (1) Is there a gen eral tendency toward underreading? (2) Does this general tendency to u nderread tuberculin skin test reactions raise some question as to the American Academy of Pediatrics, American Thoracic Society, and Centers for Disease Control and Prevention move in raising the amount of indu ration considered tuberculin positive to 15 mm in low-risk individuals ?.