Gm. Liss et al., TUBERCULOSIS INFECTION AMONG STAFF AT A CANADIAN COMMUNITY-HOSPITAL, Infection control and hospital epidemiology, 17(1), 1996, pp. 29-35
OBJECTIVE: To determine risks for tuberculin skin-test conversion amon
g employees of a community hospital in Ontario, Canada. DESIGN: Cohort
morbidity study. SETTING: Of 14 metropolitan Toronto area hospitals s
urveyed for data on tuberculin skin-test conversions, only one provide
d tuberculosis (TB) test data on all employees. Between 1991 and June
1994, 24 patients were treated at this hospital for pulmonary TB. POPU
LATION STUDIED: The population at risk included those on staff from Ja
nuary 1991 through December 1993 who previously were skin-test negativ
e; they were followed until the end of June 1994. Exposure was estimat
ed (a) based on ranking departments according to an estimate of the nu
mber of hours of direct patient contact during a typical day, and (b)
based on location of sputum-positive patients. OUTCOME MEASURE: Risks
of skin-test conversion among hospital employees with documented prior
negative skin tests. MAIN RESULTS: A total. of 809 skin-test negative
employees were followed for 2,084 person-years; 18 employees with ski
n-test conversions were identified. The overall conversion rate was 0.
9% per year (0.86 per 100 person-years). After excluding two conversio
ns attributed to contact with coworkers, the relative risk of conversi
on was 4.5 (5.5 after adjusting for age and gender) among those in the
highest exposure category (greater than or equal to 4 hours per day),
compared to those in departments ranked as having the lowest exposure
(<2 hours per day). Among those working in wards in which sputum-posi
tive patients were treated, 2.4% converted; the risk of conversion was
over six times greater than among those working on wards with no TB p
atients or in departments with no patient contact, of whom 0.4% conver
ted. Among the emergency room staff, the department in which the great
est number of sputum-positive patients were treated, at least 5% of st
aff converted. In those instances in which conversions were associated
with exposure to a specific TB patient, the involved patients had bee
n in the hospital for at least 4 days prior to being isolated. CONCLUS
IONS: These results indicate that even in a hospital with few admissio
ns due to tuberculosis, skin-test conversions associated with occupati
onal exposure may occur.