Letter to the Editor Circulating cardiac troponin T is not influenced by postural changes during venous blood collection Giuseppe Lippi a, ⁎, Gian Luca Salvagno b , Gabriel Lima-Oliveira b , Martina Montagnana b , Elisa Danese b , Gian Cesare Guidi b a Laboratory of Clinical Chemistry and Hematology, Academic Hospital of Parma, Parma, Italy b Laboratory of Clinical Biochemistry, Department of Life and Reproduction Sciences, University of Verona, Verona, Italy article info Article history: Received 1 October 2014 Accepted 4 October 2014 Available online xxxx Keywords: Troponin Preanalytical variability Biological variation The measurement of cardiospecific troponins is a mainstay for diag- nosing a broad spectrum of cardiac injuries [1]. According to recent ev- idence and recommendations, serial testing with assessment of kinetic changes is the most reliable strategy for discriminating between chronic increase of cardiospecific troponins and elevations prevalently attribut- able to acute myocardial infarction (AMI) [2]. It has recently been observed that circulating troponin T (TnT) exhibits a diurnal rhythm, which should be interpreted in relation with clinical presentation [3]. This important evidence leads to the conclusion that sampling variables should be standardized to minimize the impact of biological variation on circulating troponins and ultimately prevent misinterpretation of data. Serial sampling may be occasionally performed in different postural positions, most frequently in seated position when the patient is admit- ted to the emergency room, and in supine position thereafter, when ob- servation or treatment is initiated. Although blood collection performed in other positions is unusual, the traditional recommendation that patient should be allowed to rest in sitting or supine position for at least 15–20 min before venipuncture [4] may be frequently overlooked in short stay units and emergency care settings, where the blood is frequently drawn immediately after the patient has seated. Since body position during blood collection may induce significant variations of plasma volume and thereby affect the results of many laboratory tests [4], this study was planned to establish whether circulating TnT may be influenced by postural position during blood collection. The sample population consisted in 14 ostensibly health volunteers with measurable TnT (mean age 46 ± 12 years; 7 males, 7 females), re- cruited among the staff of the local laboratory. Venous blood sampling was performed after an overnight fast, between 9 and 12 AM, by the same experienced phlebotomist and without venous stasis. Three sequential samples were collected from each subject. The first was drawn after the subjects had rested for 25 min in supine position, the second after 20 min in conventionally seated position, and the third after 20 min in standing position. All samples were immediately transported to the laboratory, where plasma was separated with standard centrifugation. Highly-sensitive TnT was measured on lithium-heparin plasma using Cobas 6000 (Roche Diagnostics GmbH, Mannheim, Germany). The limit of blank and the 99th percentile reference limit of this immunoassay are 3.0 ng/l and 14.0 ng/l, respectively [5]. Hematocrit and hemoglobin were also assessed on whole blood anticoagulated with K 2 EDTA, using Advia 2120 (Siemens Healthcare Diagnostics, Deerfield, IL). The plasma volume change was then calculated with the formula of Dill and Costill [6]. Results were finally reported as mean and standard devi- ation (SD). Significance of differences was assessed with the Wilcoxon signed rank test, using Analyse-it (Analyse-it Software Ltd, Leeds, UK). Each patient provided written consent for being en- rolled in this study, which was performed in accord with the ethical standards established by the institution in which the experiments were performed and the Helsinki Declaration of 1975. As predictable, a significant reduction was observed for plasma volume from the supine to the sitting (-3.0 ± 2.7%; p b 0.001) and standing (-12.6 ± 4.2%; p b 0.001) positions. At variance with these findings, no significant changes were observed for circulating TnT as- suming different postural positions during blood collection (supine: 4.82 ± 2.25 ng/l; sitting, 4.78 ± 2.22 ng/l, p = 0.300; standing, 4.75 ± 2.24 ng/l, p = 0.236) (Fig. 1). No false positive cases were recorded, since no TnT value exceeded the 99th percentile reference limit of this assay. The identification of physiological sources of cardiospecific troponins elevation is crucial for appropriate interpretation of longitudinal data [7]. The results of this study may have practical implications, especially for repeated troponin testing in patients with suspected AMI, since we International Journal of Cardiology xxx (2014) xxx–xxx ⁎ Corresponding author at: U.O. Diagnostica Ematochimica, Azienda Ospedaliero- Universitaria di Parma, Via Gramsci, 14, 43126 Parma, Italy. Tel.: +39 0521 703050, +39 0521 703791. E-mail addresses: glippi@ao.pr.it, ulippi@tin.it (G. Lippi). IJCA-18999; No of Pages 2 http://dx.doi.org/10.1016/j.ijcard.2014.10.018 0167-5273/© 2014 Elsevier Ireland Ltd. All rights reserved. Contents lists available at ScienceDirect International Journal of Cardiology journal homepage: www.elsevier.com/locate/ijcard Please cite this article as: Lippi G, et al, Circulating cardiac troponin T is not influenced by postural changes during venous blood collection, Int J Cardiol (2014), http://dx.doi.org/10.1016/j.ijcard.2014.10.018