Long-Term Stability of Cancer Biomarkers in Human Serum: Biomarkers of Oxidative Stress and Redox Status, Homocysteine, CRP and the Enzymes ALT and GGT

Five frequently used biomarkers in cancer research and epidemiological studies were tested for their assay stability upon storage of serum for 12 months at -20 and -70/-80°C.The biomarker assays include reactive oxygen metabolites (ROM), the total thiol levels (TTL), homocysteine (HCy), C-reactive protein (HS-CRP) and two liver enzymes, alanine aminotransferase (ALT) and γ-glutamyltransferase (GGT).The assays for ROM, HCy, HS-CRP and GGT were stable in human serum samples at the two temperatures tested. The two other assays TTL and ALT, however, showed statistically significant differences in their stability between -20 and -80°C.Therefore, storage at -80°C is advised to maintain a reliable assay outcome when serum samples have to be stored for longer periods.