Clinical Laboratory, Department for Clinical Diagnostics and Services, and Center for Clinical Studies, Vetsuisse Faculty, University of Zurich, Winterthurerstrasse 260, 8057 Zurich, Switzerland.
Viruses. 2019 Jul 31;11(8):697. doi: 10.3390/v11080697.
Feline immunodeficiency virus (FIV) is a lentivirus of domestic cats worldwide. Diagnosis usually relies on antibody screening by point-of-care tests (POCT), e.g., by enzyme-linked immunosorbent assays (ELISA), and confirmation using Western blot (WB). We increasingly observed ELISA-negative, WB-positive samples and aimed to substantiate these observations using 1194 serum/plasma samples collected from 1998 to 2019 primarily from FIV-suspect cats. While 441 samples tested positive and 375 tested negative by ELISA and WB, 81 samples had discordant results: 70 were false ELISA-negative (WB-positive) and 11 were false ELISA-positive (WB-negative); 297 ambiguous results were not analyzed further. The diagnostic sensitivity and specificity of the ELISA (82% and 91%, respectively) were lower than those reported in 1995 (98% and 97%, respectively). The diagnostic efficiency was reduced from 97% to 86%. False ELISA-negative samples originated mainly (54%) from Switzerland (1995: 0%). Sixty-four false ELISA-negative samples were available for POCT (SNAP/WITNESS): five were POCT-positive. FIV RT-PCR was positive for two of these samples and was weakly positive for two ELISA- and POCT-negative samples. Low viral loads prohibited sequencing. Our results suggest that FIV diagnosis has become more challenging, probably due to increasing travel by cats and the introduction of new FIV isolates not recognized by screening assays.
猫免疫缺陷病毒（FIV）是全球家猫的慢病毒。诊断通常依赖于即时护理测试（POCT）的抗体筛选，例如酶联免疫吸附测定（ELISA），并用 Western blot（WB）确认。我们越来越多地观察到 ELISA 阴性、WB 阳性的样本，并旨在使用 1998 年至 2019 年主要从 FIV 可疑猫收集的 1194 份血清/血浆样本证实这些观察结果。虽然 441 份样本通过 ELISA 和 WB 检测呈阳性，375 份样本检测呈阴性，但 81 份样本的结果不一致：70 份为假 ELISA 阴性（WB 阳性），11 份为假 ELISA 阳性（WB 阴性）；297 份结果不确定，未进一步分析。ELISA 的诊断灵敏度和特异性（分别为 82%和 91%）低于 1995 年报道的（分别为 98%和 97%）。诊断效率从 97%降低到 86%。假 ELISA 阴性样本主要来源于瑞士（54%，1995 年为 0%）。64 份假 ELISA 阴性样本可用于 POCT（SNAP/WITNESS）：5 份 POCT 阳性。其中 2 份样本的 FIV RT-PCR 阳性，2 份 ELISA 和 POCT 阴性样本的 RT-PCR 弱阳性。低病毒载量禁止测序。我们的结果表明，FIV 的诊断变得更加具有挑战性，可能是由于猫的旅行增加以及筛选检测未识别的新 FIV 分离株的引入所致。
