Abstract
BackgroundRF(Rheumatoid factor) is usually thought to cause positive interference in immunoassay. Recently, our study showed that high-concentration RFs caused negative interference as well as positive interference in serum HBsAg(Hepatitis B surface antigen) ELISA(Enzyme-linked immunosorbent assay), but it is unclear that RF causing negative interference is an anomaly produced by a certain ELISA kit or a common property of most of HBsAg ELISA kits.MethodsSerum models were made by blending HBsAg-positive sera and high- or moderate-concentration RFs sera at the ratio of 1: 9, then one-step and two-step ELISA were adopted to determine HBsAg in serum models.ResultsNo matter what kind of kit used, one-step ELISA showed that HBsAg S/CO( sample/cut off) values in serum models were significantly lower than original values. Bivariate correlations tests showed decline rates of HBsAg S/CO Values were not associated to serum RF concentrations ranging from 288 to 3560 IU/mL. HBsAg converted to be negative in 69.80% serum models with original-value ranging from 1.00 to 10.00, and in 2.68% serum models with higher original-value. RF causing decline of HBsAg S/CO value provided by one-step ELISA was more obvious than that provided by two-step ELISA. ConclusionsIt is concluded that susceptibility of all HBsAg ELISA assays to interference from RF, leading to predominantly lower and in some cases "false-negative" results, and moreover, the lower the original HBsAg S/CO Value, the higher the false-negative rate.
Highlights
Rheumatoid factor (RF), a kind of autoantibody against the fragment c portion of IgG, can be of any isotype of immunoglobulins i.e. IgA, IgG, IgM, IgE, IgD[1,2]
Regardless of kit used in this study, Wilcoxon Signed Ranks Test showed that hepatitis B surface antigen (HBsAg) S/CO values of serum models were significantly lower than original values
We investigated whether moderateconcentration RFs in serum resulted in negative interference in HBsAg ELISA as well as high-concentration RFs, in addition, we speculated the negative interference was a common denominator of HBsAg ELISA kits
Summary
Rheumatoid factor (RF), a kind of autoantibody against the fragment c portion of IgG, can be of any isotype of immunoglobulins i.e. IgA, IgG, IgM, IgE, IgD[1,2]. The presences of RFs in serum can cause falsely elevated analyte levels in troponin immunoassays [5,6,7], thyroid function tests [8], tumour marker immunoassays[9,10]. RF(Rheumatoid factor) is usually thought to cause positive interference in immunoassay. Methods: Serum models were made by blending HBsAg-positive sera and high- or moderate-concentration RFs sera at the ratio of 1: 9, one-step and two-step ELISA were adopted to determine HBsAg in serum models. Conclusions: It is concluded that susceptibility of all HBsAg ELISA assays to interference from RF, leading to predominantly lower and in some cases "false-negative" results, and the lower the original HBsAg S/CO Value, the higher the false-negative rate
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