title: [Medical students at risk: prevalence and incidence of tuberculin skin test conversion].
abstract: BACKGROUND
  One third of the world population is affected by latent tuberculosis, with 9.4 million new cases; medical students have 2 to 50 times the probability of acquiring the infection.
  
  
  OBJECTIVE
  Establish the baseline prevalence of positive tuberculin skin test (TST) at the beginning of medical studies and determine the incidence and variables associated with TST conversion in medical students.
  
  
  METHODS
  Secondary analysis of a historical cohort (2007-2010) of medical students in a private Peruvian university. The TST conversion was evaluated. A binomial regression analysis was applied for each associated variable.
  
  
  RESULTS
  707 medical students were included, of whom 219 (31%) were male. The basal prevalence of reactive TST was 14.4%. Significant associations were found with the year of university entry of 2007-08 (p = 0.007) and a history of tuberculosis (p = 0.02). With a total of 822 person-years, the incidence of conversion was 2.92 cases per 100 person-years (CI95%: 1.96-4.36). The TST conversion was associated with the year of university entry (RR = 2,55; IC95%: 1,06-6,30) and a body mass index > 25 kg/m² (RR = 0,16; IC95%: 0,01-0,97). No association was detected with gender, tobacco or alcohol use.
  
  
  CONCLUSIONS
  There is evidence of a high basal prevalence of latent tuberculosis infection in medical students. The incidence rate is within expected values and high in comparison with the general population. People with BMI > 25 kg/m² have protection against a latent infection. In medical students, more attention should be paid to biosecurity.
authors.affiliation: Sociedad Científica de Estudiantes de Medicina, Escuela de Medicina, Universidad Peruana de Ciencias Aplicadas, Lima, Perú. kocfachung@gmail.com
authors.forename: Kocfa
authors.initials: K
authors.lastname: Chung-Delgado
authors.forename: Sonia
authors.initials: S
authors.lastname: Guillén-Bravo
authors.forename: Laura
authors.initials: L
authors.lastname: Navarro-Huamán
authors.forename: Rafael
authors.initials: R
authors.lastname: Quiroz-Portella
authors.forename: Alejandro
authors.initials: A
authors.lastname: Revilla-Montag
authors.forename: Andrea
authors.initials: A
authors.lastname: Ruíz-Alejos
authors.forename: Mariana
authors.initials: M
authors.lastname: Zapata-Pachas
authors.forename: Antonio
authors.initials: A
authors.lastname: Bernabé-Ortiz
mesh_terms: D005260:Female; D006801:Humans; D015994:Incidence; D055985:Latent Tuberculosis / Q000175:diagnosis / Q000453:epidemiology*; D008297:Male; D010568:Peru / Q000453:epidemiology; D015995:Prevalence; D012189:Retrospective Studies; D012306:Risk; D012307:Risk Factors; D012577:Schools, Medical; D013337:Students, Medical / Q000706:statistics & numerical data*; D014374:Tuberculin Test