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Dr. Fiedorczyk, et al reply To the Editor: We agree with Jung that several factors may influence measurements of matrix metalloproteinases (MMP) and tissue inhibitors of metalloproteinases (TIMP) in peripheral blood. Therefore our assessments were performed always under the same conditions. Blood specimens were clotted for 30 minutes without clot activator, and then centrifuged for 5 minutes at 2000 ´ g. Serum aliquots were frozen at –80°C immediately after sample collection. Aliquots for the serum MMP and TIMP measurements were thawed only once. The analysis of serum concentrations of MMP-1, MMP-3, MMP-9, MMP-13, TIMP-1, and TIMP-2 was based on a quantitative sandwich ELISA (Amersham Biosciences UK, Little Chalfont, Buckinghamshire, UK) strictly according to the manufacturer's instructions. In our patients white blood cell count before and after methotrexate treatment did not change significantly. Therefore we presume that possible release of the MMP or TIMP from white blood cells during sample preparation could not significantly hamper prognostic information of MMP and TIMP. However, we agree with Jung that interpretation of serum MMP and TIMP measurements should be performed with special caution. MALGORZATA FIEDORCZYK, MD, PhD, Assistant; PIOTR ADRIAN KLIMIUK, MD, PhD, Assistant; STANISLAW SIERAKOWSKI, MD, PhD, DSc (Med), Professor and Chair; EWA GINDZIENSKA-SIESKIEWICZ, MD, PhD, Assistant; JUSTYNA CHWIECKO, MA, PhD, Principal Technician, Department of Rheumatology and Internal Diseases, Medical University of Bialystok, M.C. Sklodowskiej 24a, 15-276 Bialystok, Poland. Address reprint requests to Dr P.A. Klimiuk. E-mail: klimp@amb.edu.pl |