Nucleosomes in serum as a marker for cell death

The concentration of nucleosomes is elevated in blood of patients with dise ases which are associated with enhanced cell death. In order to detect thes e circulating nucleosomes, we used the Cell Death Detection-ELISA(Plus) (CD DE) from Roche Diagnostics (Mannheim, Germany) (details at http:\\biochem.r oche.com). For its application in liquid materials we performed various mod ifications: we introduced a standard curve with nucleosome-rich material, w hich enabled direct quantification and improved comparability of the values within (CVinterassay:3.0-4.1%) and between several runs (CVinterassay:8.6- 13.5%), and tested the analytical specificity of the ELISA. Because of the fast elimination of nucleosomes from circulation and their l imited stability, we compared plasma and serum matrix and investigated in d etail the pre-analytical handling of serum samples which can considerably i nfluence the test results. Careless venipuncture producing hemolysis, delay ed centrifugation and bacterial contamination of the blood samples led to f alse-positive results; delayed stabilization with EDTA and insufficient sto rage conditions resulted in false-negative values. At temperatures of -20 d egreesC, serum samples which were treated with 10 mM EDTA were stable for a t least 6 months. In order to avoid possible interfering factors, we recomm end a schedule for the pre-analytical handling of the samples. As the first stage, the possible clinical application was investigated in t he sera of 310 persons. Patients with solid tumors (n = 220; mean = 361 Arb itrary Units (AU)) had considerably higher values than healthy persons (n = 50; mean = 30 AU; P = 0.0001) and patients with inflammatory diseases (n = 40; mean = 296 AU; p = 0.096). Within the group of patients with tumors, t hose in advanced stages (UICC 4) showed significantly higher values than th ose in early stages (UICC 1-3) (P = 0.0004).