title: Safety of the two-step tuberculin skin test in Indian health care workers.
abstract: BACKGROUND
  Health care workers (HCW) in low and middle income countries are at high risk of nosocomial tuberculosis infection. Periodic screening of health workers for both TB disease and infection can play a critical role in TB infection control. Occupational health programs that implement serial tuberculin skin testing (TST) are advised to use a two-step baseline TST. This helps to ensure that boosting of waned immune response is not mistaken as new TB infection (i.e. conversion). However, there are no data on safety of the two-step TST in the Indian context where HCWs are repeatedly exposed.
  
  
  METHODS
  Nursing students were recruited from 2007 to 2009 at the Christian Medical College and Hospital, Vellore, India. Consenting nursing students were screened with a baseline two-step TST at the time of recruitment. From 2007 to 2008 adverse events were recorded when reported during the TST reading (Cohort A). Nurses recruited in the final study year (2009) answered an investigator administered questionnaire assessing all likely side-effects Cohort B). This information was extracted from the case report forms and analysed.
  
  
  RESULTS
  Between 2007 and 09, 800 trainees consented to participate in the annual TB screening study and 779 did not have a past history of TB or recall a positive TST and were selected to administer TST. Of these, 755 returned for reading the result and had complete data and were included for the final analysis - 623 subjects in (cohort A) and 132 in (cohort B). These were included for the final analysis. In cohort A only 1.3% reported adverse events. In cohort B, as per the investigator administered questionnaire; 25% reported minor side effects. Itching and local pain were the most common side effects encountered. There were no major adverse events reported. In particular, the adverse events were similar in the second step of the test and not more severe.
  
  
  CONCLUSIONS
  Screening of HCWs with two-step TST for LTBI is simple and safe, and hence suitable for wide scale implementation in high-burden settings such as India.
authors.affiliation: Department of Pulmonary Medicine, Christian Medical College, Vellore 632004, Tamil Nadu, India. Electronic address: djchris@cmcvellore.ac.in.
authors.forename: Devasahayam J
authors.initials: DJ
authors.lastname: Christopher
authors.affiliation: Department of Pulmonary Medicine, Christian Medical College, Vellore 632004, Tamil Nadu, India. Electronic address: deepa.seshang@gmail.com.
authors.forename: Deepa
authors.initials: D
authors.lastname: Shankar
authors.affiliation: Department of Pulmonary Medicine, Christian Medical College, Vellore 632004, Tamil Nadu, India. Electronic address: ashima_aries@yahoo.com.
authors.forename: Ashima
authors.initials: A
authors.lastname: Datey
authors.affiliation: Johns Hopkins Bloomberg School of Public Health, Department of Epidemiology, E6133, Baltimore, MD 21205, USA. Electronic address: azwerli1@jhu.edu.
authors.forename: Alice
authors.initials: A
authors.lastname: Zwerling
authors.affiliation: McGill University, Department of Epidemiology AND Biostatistics, 1020 Pine Ave West, Montreal, QC H3A 1A2, Canada. Electronic address: madhukar.pai@mcgill.ca.
authors.forename: Madhukar
authors.initials: M
authors.lastname: Pai
keywords: Adverse events; Healthcare workers; Latent TB infection (LTBI); Tuberculin skin test (TST); Tuberculosis; Two-step tuberculin skin test