Preissner Carol M, O'Kane Dennis J, Singh Ravinder J, Morris John C, Grebe Stefan K G
Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota 55905, USA.
J Clin Endocrinol Metab. 2003 Jul;88(7):3069-74. doi: 10.1210/jc.2003-030122.
Serum thyroglobulin (Tg) measurement is a major means of detecting thyroid cancer recurrence. Unlike anti-Tg autoantibody interferences, heterophile antibody (HAB) immunoassay interferences are not well recognized by laboratorians or clinicians as a Tg assay problem. When HAB interferences occur, they usually result in false positive test results. With the current trend to treat some thyroid cancer patients with radioiodine on the basis of an elevated serum Tg result alone, this has the potential to result in unwarranted therapy. We evaluated the prevalence of HAB interference in a commonly used automated immunoassay in 1106 consecutive specimens with Tg values greater than 1 ng/ml. All Tg measurements were repeated after sample incubation in heterophile-blocking tubes (HBT). Results, which showed a more than 3 SD percentage difference from the original result, were considered to suffer from HAB interference. All possible interferences were confirmed by dilution testing. After HBT treatment, Tg levels dropped to less than 1 ng/ml in 32 specimens (P < 0.0000001), 20 of which fell to less than 0.1 ng/ml (P < 0.00002). Of these 20, 17 were anti-Tg autoantibody negative, and all 32 showed a fall of greater than 3 SD percentage (>56.91%) compared with the original result. There were also two samples that showed a significant increase of greater than 56.91% after HBT treatment. HAB interference is relatively prevalent (1.5-3%) in a commonly used automated Tg assay and can lead to clinically significant artifacts. It is currently unknown, but possible, that other immunometric Tg assays suffer from similar problems. Unless a Tg assay is confirmed to be free of HAB interference or uses additional blocking steps, as ours now does, HAB interference should be suspected if Tg results do not fit the clinical picture.
血清甲状腺球蛋白（Tg）检测是检测甲状腺癌复发的主要手段。与抗Tg自身抗体干扰不同，嗜异性抗体（HAB）免疫分析干扰并未被实验室人员或临床医生充分认识为Tg检测问题。当发生HAB干扰时，通常会导致检测结果呈假阳性。鉴于目前仅根据血清Tg结果升高就对部分甲状腺癌患者进行放射性碘治疗的趋势，这有可能导致不必要的治疗。我们评估了在1106份连续的Tg值大于1 ng/ml的标本中，常用自动化免疫分析中HAB干扰的发生率。在嗜异性阻断管（HBT）中孵育样本后，重复所有Tg检测。结果显示与原始结果的差异超过3个标准差百分比的，被认为存在HAB干扰。所有可能的干扰均通过稀释试验进行确认。经过HBT处理后，32份标本中的Tg水平降至1 ng/ml以下（P < 0.0000001），其中20份降至0.1 ng/ml以下（P < 0.00002）。在这20份标本中，17份抗Tg自身抗体阴性，所有32份标本与原始结果相比下降幅度均大于3个标准差百分比（>56.91%）。还有两份样本在HBT处理后显示显著升高超过56.91%。在常用的自动化Tg检测中，HAB干扰相对普遍（1.5 - 3%），并可能导致具有临床意义的假象。目前尚不清楚，但其他免疫比浊法Tg检测可能也存在类似问题。除非确认Tg检测无HAB干扰或采用额外的阻断步骤（如我们现在所做的），如果Tg结果与临床情况不符，应怀疑存在HAB干扰。
