Immunoassay Interference by a Commonly Used Blood Collection Tube Additive, the Organosilicone Surfactant Silwet L-720

Abstract

Background: A small number of immunoassays on several different types of analyzers were recently adversely affected by tube additives in Becton Dickinson (BD) Vacutainer® SST™, SST II, and Microtainer™ blood collection tubes. We examined the effect of a commonly used tube surfactant, Silwet™ L-720, on immunoassays and the mechanism for the interference. Methods: Immunoassays were performed on serum supplemented with Silwet L-720 on the IMMULITE™ 2500 and AxSYM™ analyzers. Direct effects of the surfactant on the chemiluminescent detection step of immunoassays and on antibody immobilization on the solid phase were examined. Results: Increasing the final surfactant concentration from 0 to 400 mg/L in serum significantly increased (∼51%) the apparent total triiodothyronine (TT3) concentrations measured on the IMMULITE 2500 but not the AxSYM analyzer. Several other competitive, but not noncompetitive, assays were also significantly affected by the surfactant on the IMMULITE 2500 analyzer. The effect was independent of serum components, and the surfactant had no direct effect on chemiluminescence reactions. The capture antibody, however, was displaced from the solid phase by incubation with solutions containing surfactant under conditions similar to the IMMULITE TT3 assay. Conclusions: The Silwet L-720 surfactant, which is used to coat the inner surfaces of tubes, appears to account for previously reported immunoassay interference by BD Vacutainer SST blood collection tubes. One of the mechanisms for the interference is the desorption of antibodies from the solid phase by the surfactant. The results identify an important factor in the selection of suitable blood collection tube surfactants and provide an approach for solving similar tube-assay interference problems in the future.

Comparison of Bayer Advia Centaur® immunoassay results obtained on samples collected in four different Becton Dickinson Vacutainer® tubes

“…18 More recently, the same investigators identi¢ed the source of the interference with the IMMULITEt 2500 TT 3 assay to be the high concentration of surfactant coated on the inner surface of the tubes, and suggested desorption of solid phase antibodies employed in the assays as the interfering mechanism. 7 In competitive solid-phase immunoassays, where antigen in the sample competes with labelled antigen for binding to solid-phase antibody, release of antibodies from the solid phase would result in a decrease in the signal which would be interpreted as a higher concentration of antigen being present. Except for CA15-3, for all immunoassays that were cited by the MHRA to give a positive bias, Advia Centaur s employs competitive solid-phase immunoassays.…”

Preanalytical quality improvement: in quality we trust

“…In response to the immunoassay interference, the manufacturer has reformulated the blood collection tubes to reduce the amount of tube additives [31] .…”

Effects of Blood Collection Tubes, including Pediatric Devices, on 16 Common Immunoassays

“…One of the interferents for immunoassays has been identified as an organosilicone surfactant (5 ). Daae et al (6,7 ) investigated the difference of hematology values in capillary and venous blood samples collected in Microtainers and Vacutainers, respectively.…”