Monitoring recency of infection helps to identify current transmission in vulnerable populations for effective disease control. We have established an in-house avidity based hepatitis C virus (HCV) recency assay based on the Monolisa Anti-HCV PLUS Version 3 ELISA kit for use of dried serum/plasma spots (DS/PS) in order to distinguish recent and long-term infections. A first panel of DS/PS (n = 218; genotype 1 n = 170 and non-genotype 1 n = 48) consisting of primary and at least one follow up sample was used to analyze the temporal changes of the Avidity Index (AI) over time. Sub-panels of longitudinal DS/PS (n = 66) and acute cases (<26 weeks; n = 34) were taken to calculate the Mean Duration of Recent Infection (MDRI) and the False Long-term Rate (FLTR), respectively. A second panel of DS/PS >104 weeks (n = 132) and a third panel of DS/PS prepared from resolved infections (≥180 days since last positive; n = 32) were used to calculate the False Recent Rate (FRR). For all genotypes, the optimal AI cut-off was determined to be 40% resulting in an MDRI of 364 days (95% CI: 223-485). FLTR was 5.9% (95% CI: 0.7-19.7), 8.3% (95% CI: 1-27), and 0% (-) and FRR was 13.6% (95% CI: 8.3-20.7), 11.7% (95% CI: 6.6-19), and 30.6% (95% CI: 9.1-61.4) for all genotypes, genotype 1, and non-genotype 1 infections, respectively. For resolved infections, the FRR was 53.1% (95% CI: 35.8-70.4). Thus, this assay performs particularly well for genotype 1 reaching a high rate of correct discriminations between infections acquired less than a year before diagnosis and those acquired earlier by applying an AI cut-off of 40%. Due to a rapid decline in avidity post resolution of an HCV infection this assay is not recommended to be used in HCV RNA negative patients.

中文翻译：

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建立干燥的血清/血浆斑点的抗丙型肝炎病毒IgG亲和力测试。

监测感染的新近度有助于确定易感人群中的当前传播情况，以有效控制疾病。我们已经建立了基于Monolisa Anti-HCV PLUS 3版ELISA试剂盒的内部基于亲和力的丙型肝炎病毒（HCV）新近度检测方法，用于使用干燥的血清/血浆斑点（DS / PS），以区分近期和长期足月感染。由第一样本和至少一个随访样本组成的第一组DS / PS（n = 218；基因型1 n = 170和非基因型1 n = 48）用于分析亲和力指数（AI）的时间变化随着时间的推移。纵向DS / PS（n = 66）和急性病例（<26周； n = 34）的子面板分别用于计算近期感染的平均持续时间（MDRI）和假长期率（FLTR） 。DS / PS的第二个面板> 使用104周（n = 132）和由解决的感染（自上次阳性以来≥180天； n = 32）制备的第三组DS / PS用于计算假近期发生率（FRR）。对于所有基因型，确定的最佳AI截止值为40％，导致MDRI为364天（95％CI：223-485）。FLTR为5.9％（95％CI：0.7-19.7），8.3％（95％CI：1-27）和0％（-），FRR为13.6％（95％CI：8.3-20.7），11.7％（所有基因型，基因型1和非基因型1感染的感染率分别为95％CI：6.6-19）和30.6％（95％CI：9.1-61.4）。对于已解决的感染，FRR为53.1％（95％CI：35.8-70.4）。因此，该检测方法对于基因型1表现特别好，在诊断前不到一年的感染与通过应用40％的AI截止值在较早获得的感染之间达到了较高的正确判别率。