The suitability of acetic acid as a safer alternative to formalin in the modified Knott test was evaluated for the diagnosis of canine heartworm (Dirofilaria immitis). Microfilaria concentration was measured by both methods and found to agree within reasonable limits (-5.84 % bias; -88.1-76.4 % limits of agreement). The level of agreement was lower when samples were prepared with a 24 h delay, but this was due to the formalin method tending to yield lower counts (-20.1 % bias; -90.5-50.2 % limits of agreement). Clearing the sample of hemoglobin improves readability and is a key feature of the modified Knott test. Hemolysis was significantly lower in the acetic acid method than the formalin method as measured by red blood cell count (6.83 × 106 and 8.79 × 106 cells/ml, respectively; p =  0.015) and absorbance at 415 nm (33.20 and 34.75, respectively; p <  0.001). Visual assessment, however, revealed little practical difference in readability. Finally, lengths of microfilariae were measured to ensure the validity of species identification by the acetic acid method; mean length was significantly shorter after acetic acid treatment (273 μm) than formalin treatment (316 μm; p <  0.001). Length reduction was also observed in acetic acid-treated Acanthocheilonema reconditum (254 μm versus 262 μm; p =  0.035), though these samples were stored prior to testing and are not directly comparable. We conclude that, while the readability of samples is similar for both methods, species differentiation must still be accomplished by other means. For most clinical purposes in determining the presence or absence of blood circulating microfilariae, however, acetic acid appears to be a suitable alternative to formalin in the modified Knott test.

中文翻译：

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在改良的Knott试验中，乙酸作为替代试剂。

在改良的Knott试验中，评估了乙酸作为福尔马林替代品的安全性的适用性，用于诊断犬心丝虫（Dirofilaria炎）。通过两种方法测量微丝aria的浓度，发现它们在合理的范围内一致（偏差为-5.84％；一致范围为-88.1-76.4％）。延迟24小时制备样品时，一致水平较低，但这是由于福尔马林法倾向于产生较低的计数（偏差为-20.1％；一致极限为-90.5-50.2％）。清除血红蛋白样本可提高可读性，并且是改进的Knott测试的关键功能。通过红细胞计数（分别为6.83×106和8.79×106个细胞/ ml，p = 0.015）和在415 nm处的吸光度（33.20和34.75，分别; p <0.001）。视觉评估，但是，在可读性上几乎没有实际差异。最后，测量微丝aria的长度，以确保通过乙酸方法鉴定物种的有效性。乙酸处理（273μm）后的平均长度显着短于福尔马林处理（316μm； p <0.001）。在乙酸处理过的棘皮动物门皮瘤中，也观察到长度减少（254μm对262μm； p = 0.035），尽管这些样品是在测试前存储的，不能直接比较。我们得出的结论是，尽管两种方法的样品可读性相似，但仍必须通过其他方式完成物种区分。但是，对于大多数临床目的而言，确定是否存在血液循环微丝aria病是