Aim: 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.
Materials & methods: 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).
Results: 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.
Conclusion: Therefore, storage at -80°C is advised to maintain a reliable assay outcome when serum samples have to be stored for longer periods.
Keywords: C-reactive protein; alanine aminotransferase; cancer biomarkers; homocysteine; hydroperoxides; stability; storage; total thiols; γ-glutamyltransferase.