Conversion Rate of Tuberculin Skin Test among Medical Students in Songklanagarind Hospital

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Sarinpant Pongpant, MD
Chanon Kongkamol, MD


Airborne and Tuberculosis (TB) control measures have been implemented in Songklanagarind hospital. The infection control unit of the hospital has provided a voluntary two-step tuberculin skin test (TST) for pre-clinical medical students and serial TST for clinical medical students. This study aimed to determine the incidence of negative outcome and booster phenomenon from two-step TST as well as the TST conversion rate from serial TST among medical students in the hospital.

Percentages of negative cases and boosting phenomenon were calculated from the two-step TST records. Conversion rates of each year were calculated from serial TST data. Then the TST conversion rates were predicted based on the Jointpoint model.

Two-step TSTs performed from 2001 to 2016 showed 40 to 100% of negative cases and zero to 14% of boosting phenomenon among 2,271 medical students. Serial TSTs from 2002 to 2016 among 665 medical students showed 60 conversion cases. Conversion rates varied from zero to 13.6%. The decline of conversion rates after the year 2006 is demonstrated in 1-Joinpoint model with statistical significance (p = 0.0129). The model corresponded with the timeline data of airborne infection control measures which were mostly implemented after 2006.

A decline in TST conversion rate was shown after 2006. This coincided with airborne infection control measures at the institute.


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How to Cite
Pongpant S, Kongkamol C. Conversion Rate of Tuberculin Skin Test among Medical Students in Songklanagarind Hospital. BKK Med J [Internet]. 2018Sep.20 [cited 2020Jul.15];14(2):17. Available from:
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