School of Veterinary Science, The University of Queensland, Gatton Campus, Gatton, QLD, Australia.
BMC Vet Res. 2012 Jul 23;8:117. doi: 10.1186/1746-6148-8-117.
Chicken red blood cells (RBCs) are commonly used in hemagglutination inhibition (HI) tests to measure hemagglutinating antibodies against influenza viruses. The use of horse RBCs in the HI test can reportedly increase its sensitivity when testing human sera for avian influenza antibodies. This study aims to compare the proportion of positives detected and the agreement between two HI tests using either chicken or horse red blood cells for antibody detection in sera of ducks experimentally infected or naturally exposed to Indonesian H5 subtype avian influenza virus. In addition, comparison with a virus neutralisation (VN) test was conducted with the experimental sera.
In the experimental study, the proportion of HI antibody-positive ducks increased slightly, from 0.57 when using chicken RBCs to 0.60 when using horse RBCs. The HI tests indicated almost perfect agreement (kappa = 0.86) when results were dichotomised (titre ≥ 4 log2), and substantial agreement (weighted kappa = 0.80) for log titres. Overall agreements between the two HI tests were greater than between either of the HI tests and the VN test. The use of horse RBCs also identified a higher proportion of antibody positives in field duck sera (0.08, compared to chicken RBCs 0.02), with also almost perfect agreements for dichotomized results (Prevalence and bias adjusted Kappa (PABAK) = 0.88) and for log titres (weighted PABAK = 0.93), respectively. Factors that might explain observed differences in the proportion of antibody-positive ducks and in the agreements between HI tests are discussed.
In conclusion, we identified a good agreement between HI tests. However, when horse RBCs were used, a higher proportion of sera was positive (titre ≥ 4 log2) than using chicken RBCs, especially during the early response against H5N1 virus. The HRBC-HI might be more responsive in identifying early H5N1 HPAI serological response and could be a recommended assay for avian influenza sero-surveillance in both wild and domestic birds.
鸡红细胞（RBC）常用于血凝抑制（HI）试验，以测量针对流感病毒的血凝抗体。据报道，在检测人血清中的禽流感抗体时，使用马 RBC 可以提高试验的敏感性。本研究旨在比较使用鸡或马 RBC 进行抗体检测时，两种 HI 试验在检测人工感染或自然感染印度尼西亚 H5 亚型禽流感病毒的鸭血清中的阳性检出率和一致性。此外，还与病毒中和（VN）试验进行了比较。
在实验研究中，使用马 RBC 时 HI 抗体阳性鸭的比例略有增加，从使用鸡 RBC 时的 0.57 增加到 0.60。当结果二分类（滴度≥4 log2）时，HI 试验几乎完全一致（kappa=0.86），对数滴度时具有实质性一致（加权 kappa=0.80）。两种 HI 试验之间的总体一致性大于任何一种 HI 试验与 VN 试验之间的一致性。使用马 RBC 还鉴定了田间鸭血清中更高比例的抗体阳性（0.08，与鸡 RBC 相比为 0.02），二分类结果（调整后的流行率和偏差 Kappa（PABAK）=0.88）和对数滴度（加权 PABAK=0.93）也几乎完全一致。讨论了可能解释观察到的抗体阳性鸭比例和 HI 试验之间一致性差异的因素。
总之，我们发现 HI 试验之间具有良好的一致性。然而，当使用马 RBC 时，与使用鸡 RBC 相比，更高比例的血清呈阳性（滴度≥4 log2），尤其是在对 H5N1 病毒的早期反应中。HRBC-HI 可能更能敏感地识别早期 H5N1 高致病性禽流感血清学反应，可作为野生和家养鸟类禽流感血清学监测的推荐检测方法。
