Allergen extracts used in subcutaneous immunotherapy can be standardized or non-standardized. Standardized extracts are available in specific biological potencies, presumably making their biological activity more consistent. The majority of allergen extracts are non-standardized and may have less consistent potencies. Non-standardized extracts are labeled as weight per volume or protein nitrogen units (PNUs). Neither method provides direct information regarding the extract’s biologic potency. The purpose of this study was to compare weight per volume versus PNU concentrations for 4 non-standardized allergen extracts prepared by two allergen manufacturers. The potencies were compared to current North American practice recommendations. The weight per volume and PNU values were provided for 4 non-standardized extracts—birch, short ragweed, dog hair and Alternaria—from HollisterStier and Stallergenes Greer. Weight per volume and PNU concentrations were compared for each of these extracts from both manufacturers. From the raw data, we calculated the corresponding PNU values for a weight per volume of 1:100 and 1:200 for each extract. Similarly, we calculated the corresponding weight per volume including a range of PNU values, for 1000, 2000, 3000, 4000 and 5000 PNU/ml. Birch extract has low PNU concentration, below 5000, for a weight per volume of 1:200 for both HollisterStier and Stallergenes Greer. In contrast, for both HollisterStier and Stallergenes Greer ragweed extract, a weight per volume of 1:200 corresponds to a PNU concentration greater than 5000. Dog extract for a weight per volume of 1:200, and even for 1:100, corresponds to very low PNUs for both companies. For Alternaria, corresponding PNU concentrations for HollisterStier is low at only 500 while over 5000 for Stallergenes Greer. Our results show variability when comparing weight per volume and PNU concentrations for both Hollister-Stier and Stallergenes Greer products. We suggest selecting a PNU dose that corresponds to a weight per volume of 1:200 as this may improve patient safety. Our recommendations for starting PNU dose for the four non-standardized extracts are 1500 for birch, 5000 for ragweed, 25 for dog, and 500 for Alternaria when using HollisterStier products; 2300 for birch, 5000 for ragweed, 1200 for dog, and 5000 for Alternaria when using Stallergenes Greer products. If the starting PNU concentration is considerably below 5000 for a weight per volume of 1:200 slow up-titration is advised. Conversely, for PNU concentrations above 5000 for weight per volume of 1:200 we suggest a maintenance dose of 5000 PNU.

中文翻译：

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非标准化过敏原提取物中单位体积重量和蛋白氮单位的比较：对皮下免疫治疗处方的影响

皮下免疫疗法中使用的过敏原提取物可以是标准化的或非标准化的。标准化提取物具有特定的生物效力，可能使它们的生物活性更加一致。大多数过敏原提取物是非标准化的，可能具有不太一致的效力。非标准化提取物被标记为每体积重量或蛋白质氮单位 (PNU)。这两种方法都没有提供有关提取物生物效力的直接信息。本研究的目的是比较由两家过敏原制造商制备的 4 种非标准化过敏原提取物的单位体积重量与 PNU 浓度。将效力与当前北美实践建议进行了比较。提供了 4 种非标准化提取物的单位体积重量和 PNU 值——桦木、短豚草、狗毛和链格孢——来自 HollisterStier 和 Stallergenes Greer。比较了来自两个制造商的每种提取物的单位体积重量和 PNU 浓度。根据原始数据，我们计算了每个提取物的每体积重量为 1:100 和 1:200 的相应 PNU 值。类似地，我们计算了相应的每体积重量，包括一系列 PNU 值，例如 1000、2000、3000、4000 和 5000 PNU/ml。对于 HollisterStier 和 Stallergenes Greer 而言，桦木提取物的 PNU 浓度较低，低于 5000，每体积重量为 1:200。相比之下，对于 HollisterStier 和 Stallergenes Greer 豚草提取物，每体积重量为 1:200 对应于大于 5000 的 PNU 浓度。每体积重量为 1:200 甚至 1:100 的狗提取物对应于两家公司的 PNU 都非常低。对于链格孢，相应的 HollisterStier 的 PNU 浓度仅为 500，而 Stallergenes Greer 的 PNU 浓度超过 5000。在比较 Hollister-Stier 和 Stallergenes Greer 产品的单位体积重量和 PNU 浓度时，我们的结果显示了可变性。我们建议选择与每体积重量 1:200 相对应的 PNU 剂量，因为这可以提高患者的安全性。使用 HollisterStier 产品时，我们建议四种非标准化提取物的起始 PNU 剂量为桦木 1500、豚草 5000、狗 25 和链格孢 500；使用 Stallergenes Greer 产品时，桦木 2300、豚草 5000、狗 1200 和链格孢 5000。如果对于每体积重量为 1:200 的起始 PNU 浓度远低于 5000，建议缓慢滴定。反过来，