Tuberculin skin test size and risk of tuberculosis development: a large population-based study in contacts.
METHODS
Contacts of tuberculosis (TB) cases identified from eight Provincial databases in British Columbia, Canada, between 1990 and 2000.


OBJECTIVE
To assess the risk of developing TB based on tuberculin skin test (TST) sizes in contacts of TB cases who did not receive treatment for latent TB infection.


METHODS
Retrospective, population-based cohort study with a 12-year follow-up.


RESULTS
Among 26,542 contacts, 180 individuals developed TB (TB rate 678/100,000). Household contacts with a TST size 0-4 mm had a TB rate of 1014/100,000, those with 5-9 mm a TB rate of 2162/100,000 and those with 10-14 mm a rate of 4478/100,000. Children aged 0-10 years with 0-4 mm had a TB rate of 806/100,000, those with 5-9 mm a TB rate of 5556/100,000 and those with 10-14 mm a rate of 42,424/100,000. Immunosuppressed contacts with TST sizes 0-4 mm had a TB rate of 630/100,000, those with 5-9 mm a TB rate of 1923/100,000, and those with 10-14 mm a rate of 1770/100,000.


CONCLUSIONS
TB rates were high for all TST sizes in household contacts, 0-10 year old contacts and immunosuppressed contacts. These contacts may benefit from treatment for latent TB infection, regardless of the size of their TST.
Morán-Mendoza
O
O
Universidad Autónoma de San Luis Potosí, San Luis Potosí, México. omoran@uaslp.mx
Marion
S A
SA
Elwood
K
K
Patrick
D M
DM
FitzGerald
J M
JM
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001955:British Columbia / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D016358:Contact Tracing; D005191:Family Characteristics; D005260:Female; D006801:Humans; D016867:Immunocompromised Host; D007223:Infant; D007231:Infant, Newborn; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012307:Risk Factors; D014374:Tuberculin Test / Q000706:statistics & numerical data*; D014376:Tuberculosis / Q000175:diagnosis* / Q000453:epidemiology* / Q000276:immunology