Dinh C H, Ng R, Grandinetti A, Joffe A, Chow D C
Department of Internal Medicine, University of Hawaii, John A Burns School of Medicine, Honolulu, HI 96816, USA.
Emerg Med J. 2006 Aug;23(8):627-9. doi: 10.1136/emj.2005.031898.
An elevated lactate level reflects impaired tissue oxygenation and is a predictor of mortality. Studies have shown that the anion gap is inadequate as a screen for hyperlactataemia, particularly in critically ill and trauma patients. A proposed explanation for the anion gap's poor sensitivity and specificity in detecting hyperlactataemia is that the serum albumin is frequently low. This study therefore, sought to compare the predictive values of the anion gap and the anion gap corrected for albumin (cAG) as an indicator of hyperlactataemia as defined by a lactate > or =2.5 mmol/l.
A retrospective review of 639 sets of laboratory values from a tertiary care hospital. Patients' laboratory results were included in the study if serum chemistries and lactate were drawn consecutively. The sensitivity, specificity, and predictive values were obtained. A receiver operator characteristics curve (ROC) was drawn and the area under the curve (AUC) was calculated.
An anion gap > or =12 provided a sensitivity, specificity, positive predictive value, and negative predictive value of 39%, 89%, 79%, and 58%, respectively, and a cAG > or =12 provided a sensitivity, specificity, positive predictive value, and negative predictive value of 75%, 59%, 66%, and 69%, respectively. The ROC curves between anion gap and cAG as a predictor of hyperlactataemia were almost identical. The AUC was 0.757 and 0.750, respectively.
The sensitivities, specificities, and predictive values of the anion gap and cAG were inadequate in predicting the presence of hyperlactataemia. The cAG provides no additional advantage over the anion gap in the detection of hyperlactataemia.
乳酸水平升高反映组织氧合受损，是死亡率的一个预测指标。研究表明，阴离子间隙作为高乳酸血症的筛查指标并不充分，尤其是在危重症和创伤患者中。阴离子间隙在检测高乳酸血症时敏感性和特异性较差的一个可能解释是血清白蛋白水平经常较低。因此，本研究旨在比较阴离子间隙和校正白蛋白后的阴离子间隙（cAG）作为乳酸≥2.5 mmol/l定义的高乳酸血症指标的预测价值。
对一家三级医院的639套实验室检查值进行回顾性分析。如果血清化学指标和乳酸检查是连续进行的，患者的实验室检查结果则纳入研究。获得敏感性、特异性和预测值。绘制受试者工作特征曲线（ROC）并计算曲线下面积（AUC）。
阴离子间隙≥12时，敏感性、特异性、阳性预测值和阴性预测值分别为39%、89%、79%和58%，而cAG≥12时，敏感性、特异性、阳性预测值和阴性预测值分别为75%、59%、66%和69%。作为高乳酸血症预测指标的阴离子间隙和cAG之间的ROC曲线几乎相同。AUC分别为0.757和0.750。
阴离子间隙和cAG在预测高乳酸血症的存在方面，其敏感性、特异性和预测值均不足。在检测高乳酸血症方面，cAG相对于阴离子间隙没有额外优势。
