The effect of rheumatoid factor on three commercial immunoassays for serum cystatin C

Cystatin C (CysC) can be used to diagnose early changes in renal insufficiency. However, there are little researches to study whether there is an interference between the level of CysC and RF. Thus, we conducted this study to investigate it. We randomly selected 30 patients with high RF (RF concentration: 552.05 ± 476.23 IU/mL) and 33 healthy subjects with RF concentration <11.1 IU/mL and CysC were measured with different reagents and instruments; Interference experiment was also be included. The results showed that the measured CysC concentration increases with increasing RF concentration in a dose-dependent manner and CysC levels are falsely increased by RF interference depends on the reagents used (CysC reagent: Whitman, Nanjing, China). Reagent manufacturers should fully consider RF interference when developing CysC reagents, and evaluate them before they are sold. When selecting CysC reagents, we should evaluate RF interference to the measurement to avoid misleading results.