ABSTRACT
【Objective】 To assess the status of HCV infection by analyzing the results of anti-HCV reactive blood samples detected by the current blood testing strategy, and discuss the viability of classified management of reactive blood donors. 【Methods】 The anti-HCV reactive samples (dual ELISA and once NAT), from May 2017 to October 2018, were divided into three groups: samples both anti-HCV and HCV RNA reactive, sole HCV RNA reactive, and sole anti-HCV reactive, and all of them were confirmed by recombinant immunoblot assay (RIBA). The positive predictive value (PPV) between groups were compared. The sensitivity, specificity and PPV for each reagent under different screening threshold (screening threshold for routine detection, optimal screening threshold, and corresponding screening threshold of the highest PPV) were analyzed. The group with low PPV were stratified by ELISA S/CO values, and PPV by different screening threshold was compared. 【Results】 There were 939 reactive samples (0.49%, 937/191 627). Confirmed by RIBA, the positive rate of anti-HCV reactive samples was 10.67%(100/937). Two samples were sole HCV RNA reactive (0.001%). Both anti-HCV+ HCV RNA reactive samples were 6.71%(63/939), with the PPV of 96.83%(61/63). Sole anti-HCV reactive samples were 93.08(874/939), with the PPV of 4.46%(39/874), among which PPV by dual and one ELISA reagent were 18.72% and 0.15%, respectively, showing statistically significant difference (P<0.05). The PPV between different S/CO values was statistically significant (P<0.05). The optimal screening thresholds of anti-HCV reagent were 9.29 and 3.97, according to the ROC curve, with significant difference noticed in PPV by different screening threshold (P<0.05). PPV in the sole anti-HCV reactive group increased from 4.46% (the routine screening threshold) to 49.35%(the optimal screening threshold), and the difference was statistically significant (P<0.05). 【Conclusion】 The blood donors with both anti-HCV and HCV RNA reactive can be determined as HCV infection and need to be permanently deferred. The S/CO value of sole anti-HCV reactive samples was positively correlated with RIBA confirmation results, and the higher the S/CO value, the greater the chances of positive confirmation are. With the current blood screening strategy, the HCV infection status of sole anti-HCV reactive blood donors can be determined by establishing a screening threshold with high PPV or adding confirmatory test.
ABSTRACT
BACKGROUND: Recombinant immunoblot assay (RIBA) or RNA test is considered to be a supplemental test for confirming a HCV infection. A correlation has been reported between the signal-to-cutoff (S/CO) ratios of a third generation HCV enzyme-linked immunosorbent assay (ELISA) and a confirmed HCV infection. This study examined the results of an evaluation of domestic anti-HCV EIA and immunoblot kit (RIBA) in Korean donors. METHODS: A total of 375,576 donor samples were tested for anti-HCV using the LG third generation HCV ELISA (LG HCD 3.0 TMB, LGphD, Korea) and HCV RNA by NAT (Biomerieux/Roche RT-PCR, 24 pool). The anti-HCV repeat reactive samples were further tested by third generation RIBA (LG HCD Confirm, LGphD, Korea). A positive result by either the nucleic acid amplification test (NAT) or RIBA was interpreted as a confirmed HCV infection. RESULTS: There were 506 out of the 375,576 donor samples (0.13%) that were anti-HCV repeat reactive (RR) by routine screening ELISA. The confirmed HCV prevalence in the donors was 0.01% (RIBA 42/375,570, RNA 36/375,570). 443 samples from the 506 repeat reactive samples in ELISA (87.6%) showed a S/CO ratio 3.6 (mean 4.40+/-0.80), compared with the negative group (mean 1.54+/-0.64). CONCLUSION: There was a good correlation between a high S/CO ratios and a confirmed HCV infection. In addition, samples showing a low S/CO ratio with an ID (Indeterminate) or negative RIBA result suggest a high probability of nonspecific reactivity in ELISA.