The significance of third-generation HCV RIBA-indeterminate, RNA-negative results in voluntary blood donors screened with sequential third-generation immunoassays
Version of Record online: 11 MAR 2004
Volume 44, Issue 3, pages 349–358, March 2004
How to Cite
Kiely, P., Kay, D., Parker, S. and Piscitelli, L. (2004), The significance of third-generation HCV RIBA-indeterminate, RNA-negative results in voluntary blood donors screened with sequential third-generation immunoassays. Transfusion, 44: 349–358. doi: 10.1111/j.1537-2995.2003.00671.x
- Issue online: 11 MAR 2004
- Version of Record online: 11 MAR 2004
- Received for publication July 28, 2003; revision received November 4, 2003, and accepted November 5, 2003.
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.