Sena S F, Syed D, Romeo R, Krzymowski G A, McComb R B
Department of Pathology, Hartford Hospital, CT 06115.
Clin Chem. 1988 Oct;34(10):2144-8.
The single-slide method used for creatinine in the Kodak "Ektachem" analyzer is far more precise than the two-slide method. We confirm that sera from patients on intravenous therapy with lidocaine exhibit a positive bias in results for creatinine but that lidocaine itself does not interfere. Instead, N-ethylglycine, a metabolite of lidocaine with a structure similar to that of sarcosine, is probably the cause. A method that allows N-ethyglycine to be measured directly is described. We followed the degree of this interference through five generations of the slide. Our investigations include two detailed comparison studies between the Kodak Ektachem 700 and the Beckman Astra analyzers. Creatinine determinations on lidocaine-treated patients when first-generation slides were used averaged 4.6 mg/L higher than determinations on these same specimens performed in the Astra. Serum creatinine results from patients not on lidocaine showed no significant difference between the two instruments. The average difference in generation 2, 3, and 4 slides was 0.24, 0.22, and 2.5 mg/L, respectively. No more than 2% of our creatinine results had a clinically significant lidocaine-related bias. We show how to identify and correct this small proportion of results that are biased because of lidocaine therapy.
柯达“Ektachem”分析仪中用于检测肌酐的单玻片法比双玻片法精确得多。我们证实，接受利多卡因静脉治疗的患者血清中肌酐检测结果存在正偏差，但利多卡因本身并无干扰。相反，结构与肌氨酸相似的利多卡因代谢产物N - 乙基甘氨酸可能是原因所在。本文描述了一种直接检测N - 乙基甘氨酸的方法。我们跟踪了五代玻片的这种干扰程度。我们的研究包括柯达Ektachem 700分析仪与贝克曼Astra分析仪之间的两项详细对比研究。使用第一代玻片时，利多卡因治疗患者的肌酐测定结果平均比在Astra分析仪上对相同标本进行的测定结果高4.6 mg/L。未使用利多卡因患者的血清肌酐结果在两台仪器之间无显著差异。第二代、第三代和第四代玻片的平均差异分别为0.24、0.22和2.5 mg/L。我们的肌酐检测结果中，因利多卡因导致的具有临床意义的偏差结果占比不超过2%。我们展示了如何识别并纠正这一小部分因利多卡因治疗而产生偏差的结果。
