[Heterophile interference: an experimental method of depleting rheumatoid factor from sera in Abidjan, Côte d'Ivoire]

Rheumatoid factor (RF) is a major source of interference in immunoassays. Several methods have been proposed to eliminate interference. We experimented with a new technique based on the depletion of rheumatoid factor from serum samples. Our study included 150 samples, 64 of them positive for RF. Depletion was performed by the adsorption of RF from the sample by latex beads sensitized with human IgG anti-RF. After precipitation of the complexes formed, the supernatant was tested for RF. Finally, we assessed the performance of this RF depletion method with two tests: ELISA Enzygnost Enzygnost anti-HBs micro-Behring and IFI falciparum Ref 75521 Biomerieux. We compared the percentages of false-negative and false-positive results of these tests before and after depletion of the RF-positive serum samples. Efficiency index is 92.2% and the performance of the two immunoassay tests improved significantly by a factor of 2 to 25 after depletion. In addition, this technique is easy, inexpensive, fast, and suitable to our limited resources as a developing country. It should be extended to other immunological tests for validation of the results.