Worth G K, Vasikaran S D, Retallack R W, Musk A A, Gutteridge D H
Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Hospital Avenue, Nedlands, Western Australia 6009.
Ann Clin Biochem. 2004 Mar;41(Pt 2):149-54. doi: 10.1258/000456304322880050.
Following the introduction of two-site immunometric assays for parathyroid hormone (PTH), the expectation of good inter-assay agreement has not been fulfilled. The reasons for this may include differences in standardization as well as fragment recognition between the assays.
PTH values for healthy individuals, patients with renal failure and patients with normal renal function and elevated parathyroid hormone (hPTH) were compared using two commercial two-site immunochemiluminometric assays (Bayer Magic-lite and DPC Immulite 2000).
Immulite results had a mean value 50.4% greater than the corresponding Magic-lite values for the whole study population with individual values ranging from 17.5% below to 118.3% above the corresponding Magic-lite value. There was no significant difference in inter-assay bias between patients with renal failure and those with normal renal function, suggesting that variable cross-reactivity with circulating disease-specific PTH fragments was not the primary cause of the observed discrepancy. Cross-reactivity with the synthetic fragment hPTH (7-84) was 34+/-5% for Magic-lite and 62+/-2% for Immulite. We also studied the stability of synthetic hPTH on storage.
The instability of synthetic hPTH over extended storage periods may affect primary standard material. The consistent inter-assay differences and the over-recovery observed in external quality assessment programmes for the Immulite assay may have best been explained by differences in calibration and the relative cross-reactivities and/or kinetics of the two assay systems for specific parathyroid fragments.
在引入甲状旁腺激素（PTH）的两点免疫测定法后，检测间良好一致性的期望并未实现。其原因可能包括标准化差异以及各检测方法之间的片段识别差异。
使用两种商业化的两点免疫化学发光测定法（拜耳Magic - lite和DPC Immulite 2000）对健康个体、肾衰竭患者以及肾功能正常但甲状旁腺激素（hPTH）升高的患者的PTH值进行比较。
对于整个研究人群，Immulite测定结果的平均值比相应的Magic - lite值高50.4%，个体值范围在比相应的Magic - lite值低17.5%至高118.3%之间。肾衰竭患者和肾功能正常患者之间的检测间偏差无显著差异，这表明与循环中疾病特异性PTH片段的可变交叉反应性不是观察到的差异的主要原因。Magic - lite与合成片段hPTH（7 - 84）的交叉反应性为34±5%，Immulite为62±2%。我们还研究了合成hPTH储存时的稳定性。
合成hPTH在延长储存期内的不稳定性可能会影响一级标准物质。Immulite测定法在外部质量评估计划中观察到的一致的检测间差异和回收率过高，最好用两种检测系统针对特定甲状旁腺片段的校准差异、相对交叉反应性和/或动力学差异来解释。
