Essay On Tst

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For the parent study, subjects had multiple QFT-GITs and three TST performed over a period of two weeks. Figure 3 illustrates the ten-day portion of the parent study that involved TSTs and which pertains to this sub-study. For this sub-study, five tests were performed: three TSTs and two QFT-GITs. On day 1, blood was collected for the first QFT-GIT. Immediately following this, PPD was injected for two TSTs, one on the left arm and one on the right arm. On day 3, transverse induration was measure at the PPD injection sites on the left and right arm. On day 8, subjects returned and had blood collected for a second QFT-GIT, again followed by injection of PPD for a third TST in either the left or the right arm. A third TST was not performed if…show more content…
An induration diameter ≥ 10 mm was interpreted as a positive test result. Results of the first two TSTs (right and left arm) were read by different readers. QFT-GIT was performed according to manufacturer’s package insert (Cellestis Limited, 2010) and as previously described (Powell, III, Whitworth, Bernardo, Moonan, & Mazurek, 2011). Blood was collected into three specially designed tubes that contained: a) heparin alone (Nil tube); b) heparin, dextrose, and phytohemagglutinin A (PHA, Mitogen tube); or c) heparin, dextrose, and a cocktail of peptides representing ESAT-6, CFP-10, and TB7.7 (TB Antigen tube). Tubes were first mixed so the entire inner surface of the tubes was coated with blood and then incubated within 12 hours of collection for 16 to 24 hours at 37˚C prior to harvesting plasma. The tubes were centrifuged, and the IFN-γ concentration in the plasma was measured by ELISA. ELISAs were performed on a Triturus automated ELISA workstation (Grifols USA, Miami, FL), using eight IFN-γ calibrators (8, 4, 2, 1, 0.5, 0.25, 0.125, and 0 IU/mL) in duplicate to create standard curves. IFN-γ concentration was calculated from a standard curve using software developed at the CDC, and test results interpreted as indicated in the Cellestis package insert and CDC guidelines (Mazurek et al., 2010; Cellestis Limited, 2010). TB Response was defined as the IFN-γ
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