[HCV antibody test methods and patterns of antibody response]

The sensitivity and specificity of the second generation ELISA (2nd ELISA) and RIBA (2nd RIBA) using c 22 and c 200 or c 33 c recombinant antigens encoded in the core and NS 3 of HCV genome have been evaluated preclinically by Ortho and Chiron (USA). Sensitivity of the assay was evaluated by determining the reactivity of 2nd ELISA and RIBA in the following panels: NANBH (N = 35) and high risk groups composed of: hemophiliacs (N = 50), IVDA (N = 50) and renal dialysis cases (N = 279). In the reactive specimens, antibody response to both c 33 c and c 22-3 was present in 93-100% whereas antibody response to 5-1-1 and c 100-3 was seen in 46-84% of these same specimens. Specificity, in turn, was evaluated using 2000 volunteer donors of 29 (1.45%) 2nd ELISA positives, 16/29 (55.2%) were confirmed by 2nd RIBA and 8/29 (27.6%) were 1 band positive (indeterminate), whereas of 27 (1.35%) 1st ELISA positive, 9/27 (33.3%) were confirmed and 4/27 (14.8%) were 1 band positive by 1st RIBA (c 100-3, 5-1-1). The relevance of various band patterns and correlation between PCR positivity with 2nd RIBA reactivity are discussed. The consistency and sensitivity of the 2nd RIBA evaluated using a densitometer are also reported.