Annual incidence of latent tuberculosis infection among newly employed nurses at a tertiary care university hospital.
OBJECTIVE
To investigate the annual rate of tuberculosis (TB) infection among newly employed nurses using both tuberculin skin test (TST) and QuantiFERON-TB Gold (QFT-G; Cellestis Limited) assay.


METHODS
A prospective cohort study involving newly employed nurses.


METHODS
A tertiary care university hospital in South Korea.


METHODS
All participants (n = 196) were tested with the TST and QFT-G assay at baseline. After 1 year, the TST and QFT-G assay were reperformed for subjects who had negative TST results at baseline and for all subjects, respectively.


RESULTS
The baseline TST and QFT-G assays were positive for 101 subjects (51.5%) and 28 subjects (14.3%), respectively; 22 subjects (11.2%) had positive results of both tests. Although the overall between-test agreement was 54.9% (k = 0.151) [95% confidence interval, 0.047-0.245]), agreement improved to 78.5% (k = 0.462 [95% confidence interval, 0.007-0.917]) for subjects who had not received bacille Calmette-Guérin vaccination. After 1 year, the TST yielded positive results for 16 (21.3%) of 75 nurses with negative baseline results, and the QFT-G assay yielded positive results for 21 (14.4%) of 146 subjects with negative baseline results. Collectively, 5 subjects (3.0%) experienced conversion to positive results with both tests, and 32 subjects (18.9%) experienced conversion to positive results with one of the tests. Neither the employing hospital department nor exposure to patients with TB affected test conversion status.


CONCLUSIONS
The poor overall agreement between TST and QFT-G results may have been caused by the confounding effect of bacille Calmette-Guérin vaccination. The annual risk of TB infection among newly employed nurses was at least 3% on the basis of results of both the TST and QFT-G test. Stricter preventive strategies against TB spread should be implemented in our hospital.
Lee
Kwangha
K
Department of Pulmonary and Critical Care Medicine, University of Ulsan College of Medicine, Asan Medical Center, Seoul 138-736, Korea.
Han
Min Kyoung
MK
Choi
Hye Ran
HR
Choi
Chang-Min
CM
Oh
Yeon-Mok
YM
Lee
Sang Do
SD
Kim
Woo Sung
WS
Kim
Dong Soon
DS
Woo
Jun Hee
JH
Shim
Tae Sun
TS
D003428:Cross Infection / Q000453:epidemiology / Q000209:etiology; D005260:Female; D006784:Hospitals, Teaching; D006801:Humans; D015994:Incidence; D017758:Infectious Disease Transmission, Patient-to-Professional / Q000706:statistics & numerical data; D055985:Latent Tuberculosis / Q000175:diagnosis* / Q000453:epidemiology*; D009726:Nurses; D011446:Prospective Studies; D056910:Republic of Korea / Q000453:epidemiology; D014374:Tuberculin Test; D055815:Young Adult