TY - JOUR T1 - Serial testing using IGRAs in a cohort of Indian nursing students JF - European Respiratory Journal JO - Eur Respir J VL - 38 IS - Suppl 55 SP - p2654 AU - Devasahayam J. Christopher AU - Prince James AU - Joy Sarojini Michael AU - Alice Zwerling AU - Madhukar Pai Y1 - 2011/09/01 UR - http://erj.ersjournals.com/content/38/Suppl_55/p2654.abstract N2 - Objectives: Evaluate how continuous Interferon gamma response varies across and within individuals over time in nursing students at a tertiary care hospital in Southern India upon annual screening for LTBI using QFT-GIT.Methods: Students were approached to participate in a longitudinal study. In addition to history, clinical log books provided detailed information on potential TB exposure prior to baseline, and between annual testing. Students underwent QFT-GIT testing in 2008, 2009 and 2010.Results: 125 nursing students completed QFT testing at 2-3 points for a total of 311 observations. We present a trajectory plot of continuous IFN-gamma across time for each participant.There exists a high degree of correlation among observations from the same individual (ICC=0.55). To account for the correlation within individuals over time, we used linear mixed models to estimate a subject specific random effects model. We found IFN-gamma results to be negatively associated with successive visits (-0.09) suggesting responses may decrease over time within individuals, independant of exposure, although this effect was small and not statistically significant. We also identified a small random effect for student (variance = 1.76) after accounting for known LTBI risk factors and TB exposure, suggesting there may be unknown factors contributing to differences in baseline IFN-gamma response across students. ER -