Background Pleural fluid pH has diagnostic, therapeutic, and prognostic implications in the management of pleural space infections and malignancy. Pleural fluid sample collection, transportation and processing are known for source of pre-analytical error which contribute to inaccuracy of measured pH with clinical implication to patient care. Some clinical practices observed locally include pleural fluid collection in sterile container for ease of other biochemistry analytes measurement in addition to pH. This study aimed to compare the differences in pleural fluid pH and other commonly ordered biochemistry analytes collected using sterile container against heparinized blood gas syringe. Methods Total 20 Pleural fluid samples were collected from patient using a procedure called thoracentesis from, with approximately 2 to 3ml of fluid directly transferred into heparinized blood gas syringe as well as in a sterile container. Both samples were then transported to Clinical Biochemistry Laboratory within an hour. Both samples were analyzed on 3 analytical systems; 1) pH on Roche COBAS b221 blood gas analyzer, 2) Glucose, Total Protein, LDH on Beckman AU System and 3) Specific Gravity on Reflectometer. Statistical analysis was performed using Analyze-It software. Results pH fluid collected in sterile container demonstrates significant high bias (absolute of 0.4 units or 5%) as compared to sample collected in heparinizes blood gas syringe. Other commonly ordered tests in fluid profile (Glucose, Total Protein, LDH and SG) demonstrate good correlation (Altman-Bland Difference Plot <5%) for pleural fluid collected in sterile container as compared to heparinized syringe. Conclusions This positive bias observed is likely attributed to air exposure in pleural fluid collection in sterile container as compared to heparinized syringe. The accuracy of measured pleural pH is critically dependent on the method of sample collection. This study highlights the need for a standardized protocol for pleural pH collection for accurate measurement.

中文翻译：

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A-116 胸腔积液 pH 值 - 我们是否正确收集和测量它？


背景 胸水 pH 对胸膜腔感染和恶性肿瘤的治疗具有诊断、治疗和预后意义。众所周知，胸水样本的采集、运输和处理是分析前误差的来源，这会导致测量的 pH 值不准确，对患者护理产生临床影响。当地观察到的一些临床实践包括将胸水收集在无菌容器中，以便于测量除 pH 之外的其他生化分析物。本研究旨在比较使用无菌容器与肝素血气注射器收集的胸水 pH 值和其他常用生化分析物的差异。方法 使用胸腔穿刺术从患者身上采集总共 20 份胸水样本，将大约 2 至 3ml 的液体直接转移到肝素血气注射器以及无菌容器中。然后两个样本在一小时内被运送到临床生化实验室。两个样品均在 3 个分析系统上进行分析； 1) Roche COBAS b221 血气分析仪上的 pH 值，2) Beckman AU 系统上的葡萄糖、总蛋白、LDH 和 3) 反射计上的比重。使用Analyze-It 软件进行统计分析。结果 与肝素化血气注射器中收集的样品相比，在无菌容器中收集的 pH 液体表现出显着的高偏差（绝对值 0.4 单位或 5%）。其他常用的液体特征测试（葡萄糖、总蛋白、LDH 和 SG）显示，与肝素化注射器相比，无菌容器中收集的胸水具有良好的相关性（Altman-Bland 差异图 <5%）。 结论 观察到的这种正偏差可能是由于与肝素化注射器相比，无菌容器中胸腔积液收集中的空气暴露所致。测量胸膜 pH 值的准确性很大程度上取决于样本采集方法。这项研究强调了胸膜 pH 值采集标准化方案的必要性，以实现准确测量。