Whole Blood Interferon-Gamma Assay for Baseline Tuberculosis Screening among Japanese Healthcare Students

BACKGROUND: The whole blood interferon-gamma assay (QuantiFERON-TB-2G; QFT) has not been fully evaluated as a baseline tuberculosis screening test in Japanese healthcare students commencing clinical contact. The aim of this study was to compare the results from the QFT with those from the tuberculin skin test (TST) in a population deemed to be at a low risk for infection with Mycobacterium tuberculosis. METHODOLOGY/PRINCIPAL FINDINGS: Healthcare students recruited at Okayama University received both the TST and the QFT to assess the level of agreement between these two tests. The interleukin-10 levels before and after exposure to M tuberculosis-specific antigens (early-secreted antigenic target 6-kDa protein [ESAT-6] and culture filtrate protein 10 [CFP-10]) were also measured. Of the 536 healthcare students, most of whom had been vaccinated with bacillus-Calmette-Guérin (BCG), 207 (56%) were enrolled in this study. The agreement between the QFT and the TST results was poor, with positive result rates of 1.4% vs. 27.5%, respectively. A multivariate analysis also revealed that the induration diameter of the TST was not affected by the interferon-gamma concentration after exposure to either of the antigens but was influenced by the number of BCG needle scars (p = 0.046). The whole blood interleukin-10 assay revealed that after antigen exposure, the median increases in interleukin-10 concentration was higher in the subgroup with the small increase in interferon-gamma concentration than in the subgroup with the large increase in interferon-gamma concentration (0.3 vs. 0 pg/mL; p = 0.004). CONCLUSIONS/SIGNIFICANCE: As a baseline screening test for low-risk Japanese healthcare students at their course entry, QFT yielded quite discordant results, compared with the TST, probably because of the low specificity of the TST results in the BCG-vaccinated population. We also found, for the first time, that the change in the interleukin-10 level after exposure to specific antigens was inversely associated with that in the interferon-gamma level in a low-risk population

Distribution map of mesh population data in Japan.

<p>Mesh population data of 380,000 one-kilometer mesh areas has been shown. These data were derived from the results of the Population Census of 2005 and include population information by age and sex. The white areas indicate that there are no inhabitants.</p

Partial correlation coefficients of the relationship between height and climatic variables on the basis of sex.

<p>TMP: Annual mean temperature.</p><p>SOLA: Annual mean solar radiation.</p><p>SUN: Annual total sunshine duration.</p><p>4000: Annual mean effective day length at 4000 lx.</p>**<p>p<0.01, *p<0.05.</p

Regression coefficients (standard errors) of predictors of height.

<p>4000: Annual mean effective day length at 4000 lx (h).</p

Partial correlation coefficients of the relationship between weight and climatic variables on the basis of sex.

<p>TMP: Annual mean temperature.</p><p>SOLA: Annual mean solar radiation.</p><p>SUN: Annual total sunshine duration.</p><p>4000: Annual mean effective day length at 4000 lx.</p>**<p>p<0.01, *p<0.05.</p

Pearson correlation matrix of climatic variables.

<p>TMP: Annual mean temperature.</p><p>SOLA: Annual mean solar radiation.</p><p>SUN: Annual total sunshine duration.</p><p>1000–10000: Annual mean effective day length at 1000 to 10000 lx.</p>**<p>p<0.0001.</p>*<p>p<0.005.</p

Pearson’s correlation coefficients of the relationship between height and climatic variables.

<p>TMP: Annual mean temperature.</p><p>SOLA: Annual mean solar radiation.</p><p>SUN: Annual total sunshine duration.</p><p>1000–10000: Annual mean effective day length at 1000 to 10000 lx.</p>**<p>p<0.0001</p>*<p>p<0.005.</p

Basic statistics for standardized height and weight.

<p>Basic statistics for standardized height and weight.</p

Distribution map of standardized height of Japanese youth.

<p>Distribution map of 13-year (1996 to 2008) average of the standardized height of (A) 14-year-old males and (B) 14-year-old females in each prefecture. The body height of Japanese youth tends to be larger in northern prefectures.</p

Basic statistics for climatic variables.

<p>Basic statistics for climatic variables.</p