TY - JOUR T1 - Influence of pre-analytic conditions on the rate of indeterminate T-SPOT®.<em>TB</em> tests JF - European Respiratory Journal JO - Eur Respir J SP - 221 LP - 222 DO - 10.1183/09031936.00179310 VL - 38 IS - 1 AU - A. Zellweger AU - J-P. Zellweger Y1 - 2011/07/01 UR - http://erj.ersjournals.com/content/38/1/221.abstract N2 - To the Editors:A prior study has demonstrated that the rate of indeterminate T-SPOT®.TB (Oxford Immunotec, Abingdon, UK) test results performed under routine field conditions was low (3.4%) [1]. Indeterminate test results were more common in individuals aged &gt;75 yrs and may be influenced by the transport conditions (cold weather in winter). Since this study was published, two technical improvements in the pre-analytic conditions were introduced. The first is the use of lithium heparinate blood sample collection tubes instead of the CPT™ Cell Preparation Tubes with sodium citrate (Vacutainer®; BD, Franklin Lakes, NJ, USA), as used in the prior study; the other is the use of the T-Cell Xtend™ reagent (Oxford Immunotec) in samples &gt;8 h old [2].The Meditest reference laboratory (Lausanne, Switzerland) receives blood samples from remote places in Switzerland, so that many samples travel overnight or for ≤36 h before being analysed. All samples that have been collected &gt;8 h earlier are processed with T-Cell Xtend. We therefore performed an updated analysis of the data from the beginning of 2010 to compare the rate of indeterminate tests … ER -