用99mTc-DTPA双血浆法评估肾小球滤过率公式的准确性

Study on accuracy of glomerular filtration rate formulas by 99mTc-DTPAdouble plasma method

目的:以99mTc-DTPA双血浆法(99mTc-DTPAdouble-phase plasma method)为“金标准”,分析CKD-EPI 2009公式及改良MDRD公式评估肾小球滤过率的准确性。方法:收集慢性肾脏病(chronickidney disease,CKD)1~5期患者166例,以99mTc-DTPA双血浆法测得值(rGFR)为“金标准”,应用CKD-EPI 2009公式和改良的MDRD公式计算eGFR,使用统计软件分析2个公式计算值与rGFR的相关性及偏倚等指标,评价公式法评估GFR在不同CKD分期中的准确性。结果:CKD1期患者中,CKD-EPI 2009公式的偏倚较改良MDRD公式小;CKD-EPI 2009公式和改良MDRD公式均与rGFR呈弱相关(P<0.01);CKD-EPI 2009公式计算值的误差小于15%、30%、50%rGFR的概率更小。CKD2期患者中,CKD-EPI 2009公式的偏倚较改良MDRD公式小;两公式均与rGFR呈中等程度相关(P<0.01);CKD-EPI 2009公式计算值的误差小于15%、30%、50%rGFR的概率更小。CKD3期患者中,CKD-EPI 2009公式的偏倚较改良MDRD公式小,两个公式均与rGFR呈强相关(P<0.01);改良MDRD公式计算值的误差小于15%、30%、50%rGFR的概率更小。CKD4期和5期患者中,CKD-EPI 2009公式的偏倚较改良MDRD公式小;两个公式与rGFR均为极强相关(P<0.01);CKD-EPI 2009公式计算值的误差小于15%、30%、50%rGFR的概率更小。在GFR<60 mL/min的患者中,CKD-EPI 2009公式诊断“肾功能下降”的灵敏度及阳性预期值更高,特异度两者相当。结论:⑴在肾功能仅轻度下降时两个公式准确性均欠佳,此时CKD-EPI 2009公式相比之下更为准确,推荐使用;⑵还需进一步改进目前的公式,以提高其对肾功能下降早期GFR的评估效能;⑶对CKD患者进行临床分期时,仅依据eGFR是可能造成分期误判的,建议联合病因-GFR-白蛋白尿分期来评估病情。

Objective:To evaluate the accuracy of glomerular filtration rate(GFR)by the CKD-EPI 2009formula and the modified MDRD formula with the 99mTc-DTPA double-phase plasma method as“gold standard”,respectively.Methods:A total of 166patients diagnosed as chronic kidney disease(CKD)were enrolled in the study.The value measured by 99mTc-DTPA double-plasma method(rGFR)was used as the"gold standard".The CKD-EPI 2009formula and the modified MDRD formula were used to calculate eGFR.Statistical software was used to analyze the correlation between the calculated values of the two formulas and the gold standard value and the bias.Then the accuracy of the two GFR formulas was evaluated.Results:Among the CKD stage 1 patients,the bias of the CKD-EPI 2009formula was smaller than that of the modified MDRD formula;both formulas were weakly correlated with the gold standard(correlation coefficients were 0.216,0.229,P<0.01,respectively);the probability of the bias of the calculated value measured bythe CKD-EPI 2009 formula less than 15%,30%,and 50%of the gold standard value was smaller.Among the CKD stage 2 patients,the bias of the CKD-EPI 2009 formula was smaller than that of the modified MDRD formula;both formulas were moderately correlated with the gold standard(correlation coefficients were 0.568,0.581,P<0.01,respectively);the probability of the bias of the calculated value measured by the CKD-EPI 2009 formula less than 15%,30%,and 50%of the gold standard value was smaller.Among the CKD stage 3 patients,the bias of the CKD-EPI 2009 formula was smaller than that of the modified MDRD formula;both formulas were strongly correlated with the gold standard(correlation coefficients were 0.664,0.670,P<0.01,respectively);the probability of the bias of the calculated value measured by the modified MDRD formula less than 15%,30%,and 50%of the gold standard value was smaller.Among the CKD stages 4 and 5 patients,the bias of the CKD-EPI 2009 formula was smaller than that of the modified MDRD formula;the CKD-EPI 2009formula and the modified MDRD formula were strongly correlated with the gold standard(correlation coefficient r was 0.808,0.802,P<0.01,respectively);the probability of the bias of the calculated value of the CKD-EPI 2009 formula less than 15%,30%,and 50%of the gold standard value wassmaller.In patients with decreased renal function with GFR<60 mL/min,the sensitivity and positive predictive valuesmeasured by the CKD-EPI 2009formulain diagnosing"decreased renal function"were higher,and the specificity was comparable.Conclusion:1.When the renal function is only slightly decreased,the accuracy of the two formulas is not good.In this condition,the CKD-EPI 2009 formula is more accurate and recommended;2.It is necessary to further improve the current formulas especially when it comes to the evaluation of the slightly declined renal function;3.When we try to identify the stage of CKD patients,according to eGFR alone may cause misclassification,so it is recommended to combine the etiology-GFR-albuminuria staging to assess the stage of CKD;4.The current formulas have limitations;thus,to obtain a highly accurate assessment of GFR,the 99mTc-DTPA dual plasma method is recommended.