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

Sarinpant Pongpant, Chanon Kongkamol


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.

tuberculin skin test, conversion rate, medical student, Songklanagarind hospital

Address Correspondence to author:
Sarinpant Pongpant, MD. Occupational health unit, Department of family medicine and preventive medicine, Faculty of Medicine, Prince of Songkla University, Songkhla, 90110, Thailand. email:

Received: May 25, 2018
Revision received: May 31, 2018
Accepted after revision: July 3, 2018
BKK Med J 2018;14(2): 17-21.

DOI: 10.31524/bkkmedj.2018.09.004

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