COMPARISON OF ELISA AND EXTENDED COMPLEMENT CDC-AHG. M Williams, D Hartzell, M Hoffman, P Kimble, M Wetmore, B Carver. HLA Laboratory, Lehigh Valley Hospital, Allentown, PA.

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The ELISA was evaluated using kits from two different manufacturers. The testing was performed by a representative of each company so as to preclude technical errors by those unfamiliar with the technique. The CDC-AHG was performed using frozen cell trays according to the manufacturers directions, but with an extended complement incubation. The AHG was diluted in the complement prior to its addition to the trays. The crossmatches were performed by the same technique, extended complement with the AHG diluted in the complement for addition to the trays.

Thirty-five percent of the samples run were negative by the ELISA screen, but positive by CDC-AHG. The sera chosen were from patients who had demonstrated specific antibody for a period of time, by CDC-AHG. The specificities were found to be IgG and verified by specific crossmatches. Six of the sera showing discordant results were repeated with the ELISA screen and, again, were reported as negative. Several of the sera were negative using the screen, but positive using the antibody ID trays. Such specificities as A1, A25, A26, B14, B55&56 as well as Cw4, were identified by CDC-AHG but not by ELISA. Patient KR had consistently demonstrated A25 & 26 antibody for over a year with A34 & 66 occasionally reacting. After the ELISA screen was repeated and found to be negative, the ID tray was then run. Only two of the reactions were considered positive. Both wells contained an A66, neither of the A25 wells, a third A66 nor an A26 well reacted. Patient RF consistently demonstrated an A1 antibody, but was repeatedly negative by ELISA screening. An ID tray was run which contained 9 wells with A1 specificity, yet there was only 1 weakly reactive well with A30,36, B45,53 specificity.

Although ELISA based testing is quick and easy, the efficacy of this technology is still limited. This, once again, points out the need to use more than one technique to determine antibody status. The ability to identify any and all antibodies our patients possess is of critical importance in being able to obtain a compatible graft with the shortest possible ischemic time.