Lorde Nathan, Gama Rousseau, Kalaria Tejas
Blood Sciences, Black Country Pathology Services, 8692 The Royal Wolverhampton NHS Trust , Wolverhampton, UK.
School of Medicine and Clinical Practice, University of Wolverhampton, Wolverhampton, UK.
Clin Chem Lab Med. 2025 Feb 3;63(7):1383-1391. doi: 10.1515/cclm-2024-1389. Print 2025 Jun 26.
To study the prevalence of trisodium citrate (NaCitrate) contamination in hypernatraemic serum samples by direct measurement of citrate and to evaluate the performance of indirect markers for identification of NaCitrate contamination.
Serum citrate was measured in all hypernatraemic serum samples (sodium ≥148 mmol/L) over a three-month period. The performance of serum chloride, sodium-chloride gap, indirect ion selective electrode (ISE)-direct ISE sodium disparity and osmolar gap in identification of NaCitrate contaminated samples was assessed against the 'gold-standard' direct citrate measurement.
In total, 27 NaCitrate contaminated samples were identified based on serum citrate concentration ≥1.5 mmol/L. The prevalence of citrate contamination was 3.1 % of hypernatraemic samples (n=875) and 0.017 % of all samples received for urea and electrolyte analysis (n=153,404). Most contaminated samples were from patients receiving haemodialysis (59.3 %), and the rest from inpatients. Cut-offs to give 100 % sensitivity were chloride ≤105 nmol/L (specificity 93.4 %), sodium-chloride gap ≥47 mmol/L (specificity 95.3 %), indirect ISE-direct ISE sodium disparity ≥3 mmol/L (specificity 81.9 %), and osmolar gap ≥39 mOsm/kg (specificity 2.8 %).
Trisodium citrate contamination is uncommon. Most contaminated samples were from patients receiving haemodialysis, likely because of contamination with citrate catheter locking solution. Screening with serum chloride or sodium-chloride gap can confidently exclude NaCitrate contamination in over 90 % of hypernatraemic samples, and in nearly all samples with sodium ≥155 mmol/L if metabolic alkalosis has been excluded. In the remaining samples, NaCitrate contamination can only be definitively confirmed or excluded by measurement of serum citrate. We propose algorithms to identify spurious hypernatraemia.
通过直接测量枸橼酸盐来研究高钠血症血清样本中枸橼酸钠（柠檬酸钠）污染的发生率，并评估用于识别枸橼酸钠污染的间接标志物的性能。
在三个月期间对所有高钠血症血清样本（钠≥148 mmol/L）进行血清枸橼酸盐测量。根据“金标准”直接枸橼酸盐测量评估血清氯、钠-氯间隙、间接离子选择性电极（ISE）-直接ISE钠差异和渗透压间隙在识别枸橼酸钠污染样本方面的性能。
根据血清枸橼酸盐浓度≥1.5 mmol/L，共识别出27个枸橼酸钠污染样本。枸橼酸盐污染的发生率在高钠血症样本中为3.1%（n = 875），在所有接受尿素和电解质分析的样本中为0.017%（n = 153,404）。大多数污染样本来自接受血液透析的患者（59.3%），其余来自住院患者。给出100%敏感性的截断值分别为：氯≤105 nmol/L（特异性93.4%）、钠-氯间隙≥47 mmol/L（特异性95.3%）、间接ISE-直接ISE钠差异≥3 mmol/L（特异性81.9%）和渗透压间隙≥39 mOsm/kg（特异性2.8%）。
枸橼酸钠污染并不常见。大多数污染样本来自接受血液透析的患者，可能是由于被枸橼酸盐导管封管液污染。用血清氯或钠-氯间隙进行筛查可以在90%以上的高钠血症样本中可靠地排除枸橼酸钠污染，并且在几乎所有钠≥155 mmol/L且已排除代谢性碱中毒的样本中也能排除。在其余样本中，只能通过测量血清枸橼酸盐来明确确认或排除枸橼酸钠污染。我们提出了识别假性高钠血症的算法。
