Quantitative (Non-qualitative) Changes of IgG Anti-Mumps After Freeze-‎Thaw Cycles

Object: The result of freeze-thaw (FT) tested sera is always doubtful, and is a matter of question which is accompanied by false negative results. To determine the effect of repeated FT cycles, on the assay results of mumps IgG antibody. This prospective laboratory study includes 25 volunteers. 25 sera underwent tests for first Mumps IgG antibody, and then were frozen at -20 degrees centigrade. One week later, they were thawed and stored again at 4 degrees centigrade for one more week when the second assays, were performed. The results for mumps IgG ELISA as an effect of two FT cycles and storage temperature were reported. The results were recorded by first and second Immune Serum Ratio (ISR) value (for first and second assay) and the percentage change of ISR. A linear regression model applied for analyzing ISR change percentage. There were three kinds of ISR value change as: 1-The stable ISR value (44%). 2-The decreasing change of ISR value (32%) mainly among males, older in age (14-19 years) and the first ISR more than the value of four. 3-The increasing change of ISR value (24%) which occurred in males 10-12 years with the first ISR value of 1-2 (lowest concentration). Based on regression model, level of the first ISR and group of test were significant factor for change percentage of ISR, but neither gender nor age, were significant. Mumps IgG antibody, as a function of two FT cycles, was affected by quantitative but not qualitative alteration. If the first ISR has value of 3-4, most probably it wills no any significant changes due to at least two FT cycles.