Short term variation of human immunoglobulin levels with an estimation of the day to day physiological variability.

In this work serum Ig levels were determined daily for 14 days in 12 subjects, every two days for 14 days in 19 subjects, every week for 1 month in 11 subjects and fortnightly in 11 subjects for 6 months. The serum IgG, IgM and IgA levels were quantitated by the linear plate method. The day-to-day reproducibility of the technique was checked for a period of one months on seven different samples. The mean coefficient of variation in the reproducibility experiments was found to be 4.8% for IgG, 8.2% for IgM and 5.2% for IgA. Since the observed variation in all groups of subjects was found to be higher than the methodological variation, it appears that physiological variability occurs in the serum Ig levels of an individual. No difference was found between the physiological variances of IgG, IgM and IgA observed in the group with daily analysis and those with determinations every two days. The physiological variations increase when longer periods are considered between consecutive determinations, but the variability of IgG and IgA in the group with fortnightly determinations is less important than that observed in the group with weekly analyses. Some evidence is presented indicating a periodic fluctuation of serum IgG and IgA levels with an amplitude of nearly 20% and with a recurrence rate of two weeks.