@article {Christopherp2654, author = {Devasahayam J. Christopher and Prince James and Joy Sarojini Michael and Alice Zwerling and Madhukar Pai}, title = {Serial testing using IGRAs in a cohort of Indian nursing students}, volume = {38}, number = {Suppl 55}, elocation-id = {p2654}, year = {2011}, publisher = {European Respiratory Society}, abstract = {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.}, issn = {0903-1936}, URL = {https://erj.ersjournals.com/content/38/Suppl_55/p2654}, eprint = {https://erj.ersjournals.com/content}, journal = {European Respiratory Journal} }