The problem of interlab variation in methods for mitochondrial disease diagnosis: enzymatic measurement of respiratory chain complexes * Frank Norbert Gellerich a, * , Johannes A. Mayr b , Sebastian Reuter a , Wolfgang Sperl b , Stephan Zierz a a Muskellabor der Neurologischen Klinik und Poliklinik, Martin-Luther Universita ¨t Halle-Wittenberg, Julius-Ku ¨hn-Strasse 7, D-06097 Halle/Saale, Germany b Labor der Universita ¨tsklinik fu ¨r Kinder- und Jugendheilkunde Salzburg, O ¨ sterreich, Germany Received 18 December 2003; received in revised form 28 May 2004; accepted 12 July 2004 Abstract Due to the large importance of mitochondrial function for numerous diseases the detection of respiratory chain defects for diagnostic purposes is an important task of mitochondrial medicine. For comparing the methods, standard mitochondrial homogenate prepared from bovine skeletal muscle was sent on dry ice to 14 labs of 8 countries. Activities of complexes I, ICIII, II, IICIII, IV (cytochrome c oxidase) and V (F 0 F 1 ATPase) as well as of citrate synthase were measured. For all enzymes the results differed at more than one order of magnitude. From eight labs we were able to compare the results with their control values for human skeletal muscle. Four labs found normal activity of cytochrome-c-oxidase whereas three labs found higher and one lab found lower activities compared to the own controls. Since all labs used different temperatures (25, 30 and 37 8C) in one lab the temperature dependencies were measured experimentally. The temperature correction did not much reduce the divergence of the results. It is concluded that differences in the lab protocols are the reason for the large variation of results. Since the experimental results strongly depend on the used method a strict standardization is necessary. q 2004 Published by Elsevier B.V. on behalf of Mitochondria Research Society. Keywords: Interlab variation; Mitochondrial disease; Respiratory chain complexes 1. Introduction 1.1. Why enzymatic measurements in the genomic and proteomic era? Since first reports linking human diseases to genetic defects of the mitochondrial genome, fast and exciting 1567-7249/$ - see front matter q 2004 Published by Elsevier B.V. on behalf of Mitochondria Research Society. doi:10.1016/j.mito.2004.07.007 Mitochondrion 4 (2004) 427–439 www.elsevier.com/locate/mito * In cooperation with: O. Boulat, H. Hansikova, M. Jaksch, L. van den Heuvel, W.S. Kunz, J. Okun, J. Schmiedel, J. Smet, B. Taylor, G.D. Vladutiu, J.C. von Kleist and M. Zeviani. * Corresponding author. Tel.: C49-345-557-3628; fax: C49- 345-557-3505. E-mail address: frank.gellerich@medizin.uni-halle.de (F.N. Gellerich).