The Effects of a Single Freeze-Thaw Cycle on Concentrations of Nutritional, Noncommunicable Disease, and Inflammatory Biomarkers in Serum Samples.

Background  The stability of biological samples is vital for reliable measurements of biomarkers in large-scale survey settings, which may be affected by freeze-thaw procedures. We examined the effect of a single freeze-thaw cycle on 13 nutritional, noncommunicable diseases (NCD), and inflammatory bioanalytes in serum samples. Method  Blood samples were collected from 70 subjects centrifuged after 30 minutes and aliquoted immediately. After a baseline analysis of the analytes, the samples were stored at - 70°C for 1 month and reanalyzed for all the parameters. Mean percentage differences between baseline (fresh blood) and freeze-thaw concentrations were calculated using paired sample t -tests and evaluated according to total allowable error (TEa) limits (desirable bias). Results  Freeze-thaw concentrations differed significantly ( p < 0.05) from baseline concentrations for soluble transferrin receptor (sTfR) (- 5.49%), vitamin D (- 12.51%), vitamin B12 (- 3.74%), plasma glucose (1.93%), C-reactive protein (CRP) (3.45%), high-density lipoprotein (HDL) (7.98%), and cholesterol (9.76%), but they were within respective TEa limits. Low-density lipoprotein (LDL) (- 0.67%), creatinine (0.94%), albumin (0.87%), total protein (1.00%), ferritin (- 0.58%), and triglycerides (TAG) (2.82%) concentrations remained stable following the freeze-thaw cycle. In conclusion, single freeze-thaw cycle of the biomarkers in serum/plasma samples after storage at - 70°C for 1 month had minimal effect on stability of the studied analytes, and the changes in concentration were within acceptable limit for all analytes.