IDIM, Universidad del Salvador, Libertad 836, C1012 AAR, Buenos Aires, Argentina.
Osteoporos Int. 2021 Oct;32(10):2111-2114. doi: 10.1007/s00198-021-05950-2. Epub 2021 Apr 24.
Parathyroid hormone (PTH) measurement using immunoassays is inherently vulnerable to interferences due to the presence of different proteins such as heterophile antibodies, human anti-animal antibodies, auto-analyte antibodies, the rheumatoid factor, and others. The frequency of immunoassay interference can be as high as 6%. We report the case of a patient showing persistent high levels of PTH without impact on calcium and bone metabolism.
The patient was a 59-year-old asymptomatic woman who consistently showed elevated PTH levels (385-482 pg/ml) using the Roche Elecsys (Cobas e-411) and ADVIA Centaur assays, with normal calcium, phosphorus, vitamin D, and renal function parameters. She had no history of fractures, nephrolithiasis, gastrointestinal complaints, renal insufficiency, or autoimmune diseases. Her physical examination revealed no abnormalities. Biomarkers of bone metabolism were within the reference range. To rule out falsely elevated PTH levels, we initially performed serial dilutions using both assays, which revealed nonlinearity. After a polyethylene glycol precipitation test, less than 10% of PTH was recovered from the supernatant. These results suggested the presence of heterophile antibodies as the cause of the falsely elevated PTH levels.
Physicians should be aware of this issue in order to avoid unnecessary clinical investigations and inappropriate treatments.
由于存在不同的蛋白质，如异嗜性抗体、人抗动物抗体、自身分析物抗体、类风湿因子等，甲状旁腺激素 (PTH) 的免疫测定法在测量时本质上容易受到干扰。免疫测定法干扰的频率可能高达 6%。我们报告了一例患者持续出现高 PTH 水平而无钙和骨代谢影响的病例。
患者为 59 岁无症状女性，罗氏 Elecsys (Cobas e-411) 和 ADVIA Centaur 检测始终显示 PTH 水平升高 (385-482 pg/ml)，钙、磷、维生素 D 和肾功能参数正常。她没有骨折、肾结石、胃肠道投诉、肾功能不全或自身免疫性疾病的病史。她的体格检查无异常。骨代谢标志物在参考范围内。为排除 PTH 水平假性升高，我们最初使用两种检测方法进行了连续稀释，结果显示为非线性。聚乙二醇沉淀试验后，上清液中回收的 PTH 不到 10%。这些结果提示存在异嗜性抗体是导致 PTH 水平假性升高的原因。
医生应该意识到这个问题，以避免不必要的临床检查和不适当的治疗。
