Department of Renal Medicine, Changi General Hospital, Singapore, Singapore.
School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Aberdeen, UK.
Intern Med J. 2022 Sep;52(9):1531-1537. doi: 10.1111/imj.15396. Epub 2022 Jun 2.
The anion gap (AG) is often used to evaluate acid-base disorders. The reference interval for normal AG is used to differentiate between raised (gap) or normal AG (non-gap) acidosis. Historically accepted AG values may not be valid with the evolution of modern analytical techniques and the reference interval requires revalidation.
To determine the reference interval for AG based on current laboratory techniques.
During a health-screening exercise, 284 participants with no major illnesses volunteered surplus blood for analysis. The samples were tested in an internationally accredited clinical laboratory. AG was calculated by [Na ] - [Cl ] - [HCO ] and AG by [Na ] + [K ] - [Cl ] - [HCO ]. The reference interval was determined at 2.5th-97.5th percentiles. Analysis was further undertaken for a subcohort of 156 individuals with no suboptimal health indicators.
Median age was 35 years, body mass index 23.4 kg/m and the glomerular filtration rate was 106 mL/min/1.73 m . Median AG was 13 mmol/L and the reference interval for normal AG is 10-18 mmol/L with a 99% level of confidence. Statistically significant differences in AG were detected for sex, race, obesity and serum albumin, but the difference was 1 mmol/L between subgroups. The reference interval was the same for the sub-cohort of 156 individuals. Median AG was 17.7 mmol/L and reference interval was 14.6-22.5 mmol/L.
The AG reference interval of 10-18 mmol/L is valid for laboratories with similar reference intervals for electrolytes. Lower values expected with current laboratory techniques were not observed. The median AG of 13 mmol/L may be used to differentiate gap acidosis, non-gap acidosis or mixed acid-base disorders.
阴离子间隙（AG）常用于评估酸碱失衡。正常 AG 的参考区间用于区分升高的（间隙）或正常 AG（非间隙）酸中毒。随着现代分析技术的发展，历史上接受的 AG 值可能不再有效，参考区间需要重新验证。
根据当前实验室技术确定 AG 的参考区间。
在一项健康筛查活动中，284 名没有重大疾病的参与者自愿捐献多余的血液进行分析。这些样本在一家获得国际认可的临床实验室进行测试。AG 通过 [Na+] - [Cl-] - [HCO3-] 计算，AG 通过 [Na+] + [K+] - [Cl-] - [HCO3-] 计算。参考区间在第 2.5-97.5 百分位数确定。进一步对 156 名没有亚健康指标的亚组进行了分析。
中位年龄为 35 岁，体重指数为 23.4kg/m，肾小球滤过率为 106mL/min/1.73m。中位 AG 为 13mmol/L，正常 AG 的参考区间为 10-18mmol/L，置信度为 99%。AG 性别、种族、肥胖和血清白蛋白存在统计学差异，但亚组之间差异为 1mmol/L。亚组 156 人的参考区间相同。中位 AG 为 17.7mmol/L，参考区间为 14.6-22.5mmol/L。
对于具有相似电解质参考区间的实验室，10-18mmol/L 的 AG 参考区间是有效的。目前实验室技术并未观察到预期的较低 AG 值。13mmol/L 的中位 AG 值可用于区分间隙性酸中毒、非间隙性酸中毒或混合性酸碱平衡紊乱。
