Background: Differentiating between true and pseudohyperkalaemia is essential for patient management. Common causes of pseudohyperkalaemia include haemolysis, blood cell dyscrasias and EDTA contamination . One approach to differentiate between them is by checking the renal function, as it is believed that true hyperkalaemia is rare with normal function. This is logical, but there is limited published evidence to support it. The aim of this study was to investigate the potential role of the eGFR in differentiating true from pseudohyperkalaemia.

Methods: GP serum potassium results >6.0 mmol/L from 01/01/2017-31/12/2017, with a repeat within 7 days, were included. Entries were retrospectively classified as true or pseudohyperkalaemia based on the potassium reference change value and reference interval. If the initial sample had a FBC, it was classified as normal/abnormal to remove blood cell dyscrasias. Different eGFR cut-points were used to determine the potential in differentiating true from pseudohyperkalaemia.

Results: 272 patients were included with potassium results >6.0 mmol/L, with 145 classified as pseudohyperkalaemia. At an eGFR of 90 ml/min/1.73 m2, the negative predictive value (NPV) was 81% (95% CI: 67-90%), this increased to 86% (95% CI: 66-95%) by removing patients with abnormal FBC. When only patients with an initial potassium ≥6.5 mmol/L were included (regardless of FBC), at an eGFR of >90 ml/min/1.73 m2, the NPV was 100%. Lower NPVs were seen with decreasing eGFR cut-points.

Conclusion: Normal renal function was not associated with true hyperkalaemia, making the eGFR a useful tool in predicting true from pseudohyperkalaemia, especially for potassium results ≥6.5 mmol/L

背景：区分真性和假性高钾血症对患者管理至关重要。假性高钾血症的常见原因包括溶血、血细胞恶液质和 EDTA 污染。区分它们的一种方法是检查肾功能，因为人们认为真正的高钾血症在功能正常的情况下很少见。这是合乎逻辑的，但支持它的已发表证据有限。本研究的目的是调查 eGFR 在区分真性高钾血症和假性高钾血症中的潜在作用。

方法：纳入 2017 年 1 月 1 日至 2017 年 1 月 12 日 31 日，7 天内重复的 GP 血清钾结果 >6.0 mmol/L。根据钾参考变化值和参考区间，将条目回顾性分类为真性或假性高钾血症。如果初始样本有 FBC，则将其分类为正常/异常以去除血细胞恶液质。使用不同的 eGFR 切点来确定区分真性高钾血症和假性高钾血症的潜力。

结果：272例患者血钾>6.0 mmol/L，其中145例为假性高钾血症。在 eGFR 为 90 ml/min/1.73 m2 时，阴性预测值 (NPV) 为 81% (95% CI: 67-90%)，通过去除FBC异常的患者。当仅包括初始钾≥6.5 mmol/L 的患者时（不考虑 FBC），在 eGFR > 90 ml/min/1.73 m2 时，NPV 为 100%。随着 eGFR 分界点的降低，可以看到较低的 NPV。

结论：正常肾功能与真性高钾血症无关，使 eGFR 成为预测假性高钾血症的有用工具，尤其是钾结果≥6.5 mmol/L