Performance of the tuberculin skin test and interferon-gamma release assay for detection of tuberculosis infection in immunocompromised patients in a BCG-vaccinated population.
BACKGROUND
Interferon-gamma release assay (IGRA) may improve diagnostic accuracy for latent tuberculosis infection (LTBI). This study compared the performance of the tuberculin skin test (TST) with that of IGRA for the diagnosis of LTBI in immunocompromised patients in an intermediate TB burden country where BCG vaccination is mandatory.


METHODS
We conducted a retrospective observational study of patients given the TST and an IGRA, the QuantiFERON-TB Gold In-Tube (QFT-IT), at Severance Hospital, a tertiary hospital in South Korea, from December 2006 to May 2009.


RESULTS
Of 211 patients who underwent TST and QFT-IT testing, 117 (55%) were classified as immunocompromised. Significantly fewer immunocompromised than immunocompetent patients had positive TST results (10.3% vs. 27.7%, p 0.001), whereas the percentage of positive QFT-IT results was comparable for both groups (21.4% vs. 25.5%). However, indeterminate QFT-IT results were more frequent in immunocompromised than immunocompetent patients (21.4% vs. 9.6%, p 0.021). Agreement between the TST and QFT-IT was fair for the immunocompromised group (kappa = 0.38), but moderate agreement was observed for the immunocompetent group (kappa = 0.57). Indeterminate QFT-IT results were associated with anaemia, lymphocytopenia, hypoproteinemia, and hypoalbuminemia.


CONCLUSIONS
In immunocompromised patients, the QFT-IT may be more sensitive than the TST for detection of LTBI, but it resulted in a considerable proportion of indeterminate results. Therefore, both tests may maximise the efficacy of screening for LTBI in immunocompromised patients.
Kim
Eun Young
EY
Department of Internal Medicine, Yonsei University College of Medicine, 250 Seongsanno, Seodaemun-gu, Seoul, Republic of Korea. NARAE97@yuhs.ac
Lim
Ju Eun
JE
Jung
Ji Ye
JY
Son
Ji Young
JY
Lee
Kyung Jong
KJ
Yoon
Yoe Wun
YW
Park
Byung Hoon
BH
Moon
Jin Wook
JW
Park
Moo Suk
MS
Kim
Young Sam
YS
Kim
Se Kyu
SK
Chang
Joon
J
Kang
Young Ae
YA
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001500:BCG Vaccine / Q000008:administration & dosage; D005260:Female; D006801:Humans; D016867:Immunocompromised Host; D007371:Interferon-gamma / Q000097:blood*; D055985:Latent Tuberculosis / Q000175:diagnosis* / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D056910:Republic of Korea / Q000453:epidemiology; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014374:Tuberculin Test; D055815:Young Adult
D001500:BCG Vaccine; D007371:Interferon-gamma