Antiglobulin test using an immunoenzyme method

An enzyme-linked antiglobulin test (ELAT) is described. All reagents are commercially available. The antiglobulin reagent is a monoclonal anti-IgG conjugated with alkaline phosphatase. The substrate (p-nitrophenylphosphate) is stable and innocuous. The procedure requires long incubations, particularly between red cells and the enzyme-conjugated antibody. However most of the time actively spent by the technician is consumed by washing procedures (LAV). These may be avoided by using density gradient centrifugation (CSG). ELAT is significantly more sensitive than agglutination, using either washing or gradient centrifugation (P = 0.002 and P = 0.0005, respectively). Moreover ELAT-CSG is significantly more sensitive than ELAT-LAV (P = 0.03). CSG yields better reproducibility and probably avoids some of the spontaneous elution of the primary and/or secondary antibody which may occur during washing.