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The significance of third‐generation HCV RIBA‐indeterminate, RNA‐negative results in voluntary blood donors screened with sequential third‐generation immunoassays
Author(s) -
Kiely Philip,
Kay Deborah,
Parker Susan,
Piscitelli Lisa
Publication year - 2004
Publication title -
transfusion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.045
H-Index - 132
eISSN - 1537-2995
pISSN - 0041-1132
DOI - 10.1111/j.1537-2995.2003.00671.x
Subject(s) - indeterminate , immunoassay , rna , medicine , antibody , virology , immunology , biology , biochemistry , mathematics , pure mathematics , gene
BACKGROUND: One of the problems associated with the use of anti‐HCV immunoblot assays is the inter‐pretation of indeterminate results without detectable HCV RNA. The purpose of this study was to examine the significance of third‐generation RIBA (RIBA‐3)‐indeterminate, RNA‐negative results in voluntary blood donors. STUDY DESIGN AND METHODS: Since June 2000 all Australian Red Cross Blood Service testing sites have used an anti‐HCV sequential immunoassay testing strategy whereby donors who are reactive on the primary screening immunoassay are tested on a secondary immunoassay and if reactive on both assays, further tested by immunoblot. From the four testing sites that use RIBA‐3, the result profiles of donors who were RIBA‐3‐indeterminate, HCV RNA‐negative were analyzed. RESULTS: From 2,661,786 donations screened for anti‐HCV during the study period, 102 RIBA‐3‐indeterminate, RNA‐negative donors were identified, most of whom were reactive to either c33p (69.6%) or c22p (27.5%). The RIBA‐3‐indeterminate, RNA‐negative donors showed a significantly higher screening immunoassay signal strength to assay cutoff (S/CO) distribution than those with biologic false‐reactive (BFR) results (1.853 vs. 1.524, p < 0.05) but a significantly lower distribution than RIBA‐3‐positive, RNA‐negative (1.853 vs. 4.546, p < 0.05) or RNA‐positive (1.853 vs. 6.467, p < 0.05) donors. The RIBA‐3‐indeterminate, RNA‐negative donors showed a similar distribution of c33c and c22p band intensities compared with RIBA‐3‐positive, RNA‐negative donors but significantly lower distribution of band strengths compared to the RIBA‐3‐positive, RNA‐positive group. Compared to the indeterminate donors with previous anti‐HCV‐negative or BFR results, the indeterminate donors not previously screened for anti‐HCV showed higher immunoassay S/CO ratio distributions, a higher proportion with c22p reactivity (16.2% vs. 36.7%), and higher frequency of risk factors (46.4% vs. 75.0%). CONCLUSIONS: Our analysis suggests that a combination of indicators can be used to help clarify RIBA‐3‐indeterminate, RNA‐negative results. Specifically, donors with high S/CO ratios on a screening immunoassay, RIBA‐3 reactivity to c22p or c33c with band intensity of 2+ or greater, without a previous history of negative or BFR donations and with an identifiable risk factor, have a high probability of representing true anti‐HCV rather than nonspecific reactivity.