Validation of an indirect ELISA employing a chimeric recombinant gag and env peptide for the serological diagnosis of equine infectious anemia

Abstract

The National Reference Center for equine infectious anemia (EIA) validated a commercial ELISA (Eradikit^® EIAV Indirect ELISA, In3diagnostic^®, Turin, Italy) employing a chimeric recombinant gag and env peptide for the detection of EIA virus antibodies, following the guidelines of the World Organization for Animal Health. The validation parameters evaluated were: analytical sensitivity (Se) and specificity (Sp); diagnostic Se and Sp; precision, based on repeatability and reproducibility through the estimation of the standard deviation (SD) and the coefficient of variation (CV); accuracy, estimated from a multiple K and relative Sp and Se with respect to those of the agar gel immunodiffusion test (AGIDT). Positive and negative predictive values were also defined. The assay showed a high specificity and a limit of detection of 1.43 log₁₀ major than AGIDT. Diagnostic Se was 100% and Sp was 99.3%, while SD values ranged from 1.58 to 5.01 with a CV between 2.8% and 28.8%. Multiple K was 0.98 and relative Se and Sp were respectively 99.1% and 100%. The assay proved to be robust and to possess a high sensitivity in detecting first antibodies produced at onset of infection as well as high analytic and diagnostic Se and Sp values, confirming it as a serological assay fit for purpose within EIA surveillance programs.

Keywords: Chimeric recombinant peptide; ELISA; Equine infectious anemia; Screening test; Surveillance; Validation; gag and env.