[The importance of using various methods in the determination of serum immune complex levels]

Concentration of immune complexes (IC) in the serum of patients with various diseases (glomerulonephritis systemic lupus erythematosus--SLE, rheumatoid arthritis--RA and with positive antibodies to human immunodeficiency virus--HIV+) has been determined using two methods: PEG precipitation and laser nephelometry (NL) of binding to Latex = C1 12q complement components in aqueous media. The presence of antiimmunoglobulin antibodies, that is, rheumatoid factor (RF) and its eventual effect on the precision of measurement of IC using LN C1q method has been determined by LN-Latex RF method. The results have shown that the increased IC values obtained by one method can be within physiological levels if the other method was applied and vice versa. Depending on the group of examinees such negative correlation ranged from 33% to 64%. This is the result of already known limitations of the studied methods and confirms the necessity of simultaneous application of different methods for determination of IC concentration. Regardless of anticomplementary activity of serum rheumatoid factor its presence in the serum has not shown to have any effect on the precision of determination of IC concentration using IC by LN- C1q method.