Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, 77843, USA.
Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, 30602, USA.
Vet Parasitol. 2021 Jan;289:109302. doi: 10.1016/j.vetpar.2020.109302. Epub 2020 Dec 10.
Antigen enzyme-linked immunosorbent assay tests are widely used for the diagnosis of heartworm infection in dogs. While commercially-available heartworm antigen tests have high sensitivity and specificity, false-negative test results can occur in dogs with low worm burdens, female-only infections, or prior to patency. The use of immune complex dissociation (ICD) methods have demonstrated increased sensitivity in the detection of Dirofilaria immitis antigens and the reversal of false-negative antigen results. However, there are concerns pertaining to false-positive antigen results due to infections of other nematode parasites, especially post-ICD. Therefore, this study evaluated the effect of heat-treatment on serum samples of dogs experimentally-infected with Dirofilaria repens during the course of infection, to assess for potential cross-reactivity on heartworm antigen tests. Archived serum samples from three dogs experimentally-infected with D. repens were utilized. All samples were tested for cross-reactivity pre- and post-heat-treatment using the DiroCHEK® Heartworm Antigen test kit throughout infection (day -9 through 404 days post-infection; dpi). All heat-treated samples tested false-positive starting at 164 dpi and continuing through 404 dpi, thereby testing positive prior to patency. No cross-reactivity was observed for any dog at any time point prior to heat-treatment. Our results suggest that the ICD method decreased the specificity of heartworm antigen tests and caused cross-reactivity of serum from dogs experimentally infected with D. repens. In conclusion, heat-treatment of serum in areas co-endemic for D. repens and D. immitis has limited clinical value, and should be used with caution.
抗原酶联免疫吸附试验广泛用于犬心丝虫感染的诊断。虽然市售的心丝虫抗原检测具有高灵敏度和特异性，但在低虫负荷、仅雌性感染或未开放前，可能会出现假阴性检测结果。免疫复合物解离（ICD）方法的应用已证明在检测犬恶丝虫抗原方面具有更高的灵敏度，并能逆转假阴性抗原结果。然而，由于其他线虫寄生虫的感染，特别是 ICD 后，存在假阳性抗原结果的担忧。因此，本研究评估了在犬恶丝虫感染过程中对感染 Dirofilaria repens 的犬血清样本进行热处理对心丝虫抗原检测的潜在交叉反应的影响。本研究使用了三只犬实验感染 Dirofilaria repens 的存档血清样本。在整个感染过程中（感染前 9 天至 404 天），使用 DiroCHEK®心丝虫抗原检测试剂盒对所有样本进行热处理前后的交叉反应性检测。所有热处理样本在 164 dpi 开始出现假阳性，并持续到 404 dpi，因此在未开放前就呈阳性。在热处理之前，任何一只犬在任何时间点都没有观察到交叉反应。我们的结果表明，ICD 方法降低了心丝虫抗原检测的特异性，并导致了犬实验感染 D. repens 的血清发生交叉反应。总之，在 D. repens 和 D. immitis 共同流行地区，血清的热处理对临床价值有限，应谨慎使用。
