改良MDRD公式、血清肌酐、肌酐清除率、胱抑素C及尿微量白蛋白在慢性肾病早期诊断中的应用

目的采用估算的肾小球滤过率（eGFR）在慢性肾病（CKD）患者中分期，用于比较各期血清肌酐（Scr）、肌酐清除率（Ccr）、胱抑素C（CystatinC）及尿微量白蛋白（mAlb）的异常率，分析该五项指标在慢性肾病早期诊断中的应用。方法Scr和尿肌酐采用苦味酸动力学法测定，血清Cystatinc采用胶乳增强免疫比浊法，尿mAlb采用速率散射比浊法，eGFR主要基于Scr及年龄而采用简化的肾病膳食改良试验（MDRD）方程进行计算。结果CKD患者随着eGFR的降低，Nor、Ccr、CystatinC三指标平均水平在各期间的差异有统计学意义（P〈0．05）。而尿mAlb在各期内离散度很大，各水平间差异无统计学意义（P〉0．05）。当eGFR≥90mL／min时，Ccr、CystatinC、尿mAlb与Scr的异常率分别为18．42％、22．37％、25．0％、0，前三者与Scr比较差异均有统计学意义（P〈0．05），而三者间异常率比较差异无统计学意义（P〉0．05）；当eGFR在60-89mL／min时，异常率分别为28．89％、46．67％、22．22％、2。22％，前三者与Scr比较差异同样有统计学意义（P〈0．05）；当eGFR在30～59mL／min时，异常率分别为90．48％、76．19％、57．14％、52．38％，Ccr及CystatinC异常率与Scr比较差异有统计学意义（P〈0．05），Ccr异常率最为显著；在eGFR≤29mL／min时，Scr、Ccr、CystatinC、尿mAlb四项指标的异常率均为100％。结论当eGFR〉60mL／min，Scr不能反映GFR的下降，eGFR高估了实际的GFR，而应增加CystatinC和Ccr来评价肾脏功能；当eGFR在30-59mL／min，Scr、CystatmC、Ccr及mAlb能检出一半以上的病例异常，其中CystatinC及Ccr能检出3／4GFR下降的病例，因此对于此期Scr正常，应增加CystatinC和Ccr检验来评价肾脏功能，必要时应检测^99mTc—DTPA清除率来检测GFR值；当eGFR％29mL／min，各指标都反映肾脏功能受损。对于出现尿mAlb的患者，说明肾脏早期受到损伤，24h尿mAlb量的多少不反映GFR的降低，应增加Cysta—tinC、Ccr及eGFR来判断CKD分期，必要时应检测^99mTc-DTPA清除率来检测GFR值。

Clinical application of simplified MDRD formula, serum creatinine, creatinine clearance rate, eystatin Cand urinary microalbumin in early diagnosis of chronic kidney disease

Objective To perform staging of chronic kidney disease (CHD) with estimated glo-merular filtration rate (eGFR), compare the abnormality rates of serum creatinine (Scr), ereatinine clearance rate (Ccr), cystatin C and urine microalbumin (mAlb) in each stage, so as to investigate their clinical application in early diagnosis of CKD. Methods The levels of creatinine in serum and urine were determined with Jaffe method; serum cystatin C was determined by applying latex-enhanced im-munoturbidimetry; urine mAlb was determined with the rate nephelometry; and eGFR was calculated by using simplified Modification of Diet in Renal Diease (MDRD) formula,which was mainly based on the serum creatinine concentration and patient age. According to the guidelines of Kidney Disease Out-come Quality Initiative (K/DOQI) published by American National Kidney Foundation (NKF), all CKD cases were classified into 5 stages based on eGFR. Results With the decrease of eGFR, the differences in mean levels of Scr, Ccr and cystatin C showed statistical significance (P<0.05), while the divergency of urine mAlb was great,and there were no statistical differences of urine mAlb levels among different stages (P>0.05). When eGFR≥90 mL/min, the abnormality rates of Ccr,cystatin C, urine malb and Scr were 18.42% ,22.37% ,25.0% and 0,respectively. The difference between the for-mer three items and Scr were statistically significant (P<0.05) ,but the differences among the former three parameters did not achieve statistical significance (P>0.05). When eGFR was within 60-89 mL/ rain,the abnormality rates of Ccr,cystatin C,urine mAlb and Src were 28.89% ,46.67% ,22.22% and2.22% ,respectively (P<0.05). The difference between the former three items and Scr was also sta-tistically significant (P<0.05). When eGFR was within 30-59 mL/min,the abnormality rates of Ccr, systatin C,urine mAlb and Scr were 90.48% ,76.19% ,57.14% and 52.38% ,respectively. The differ-ence of abnormality rate between Ccr,cystatin C and Scr was statistically significant (P<0.05). The abnormality rate of Ccr was the most prominent. When eGFR≤29 mL/min,the abnormal rates of Scr, Ccr,cystatin C and urine mAlb were all 100%. Conclusion When eGFR excels 60 mL/min, Scr can't reflect the decline of GFR and eGFR overestimates the actual level of GFR,at this time cystatin C and Ccr should be added to evaluate the kidney function. When eGFR is within 30-59 mL/min,Scr,cystatin C,Ccr,and mAlb can detect more than half of abnormal eases; in which cystatin C and Ccr can detect three fourth of cases wth a decrease of GFR. Thus, for normal Scr at this stage, cystatin C and Ccr should also be included to evaluate the kidney function. If necessary,the clearance rate of 99mTc-DTPA should be determined to measure the GFR level. When eGFR was below 29 mL/min, each parameter can be used to show the damage of kidney function. For patients with positive urine mAlb, renal injury occurs in early stage,and the amount of urine mAlb in 24 h does not reflect the decrease of GFR. Cys-tatin C,Ccr,and eGFR should be added to estimate the stage of CKD,and the clearance rate of 99mTc-DTPA should be determined to measure the GFR level if necessary.