Correction And Clinical Value Of Gates Method For The Determination Of Glomerular Filtration Rate

Objective:Glomerular filtration rate（GFR）measurement using radionuclide technetium 99m labeled Diethylenetriamine pent acetic acid(^99mTc-DTPA)renal scintigraphy Gates method is one of the routine projects in nuclear medicine imaging.This study aims to1.Establish a standardized inspection process,improve the accuracy of GFR determination by Gates method though establishing correction equation and quality control;2.Explore the feasibility of Gates method in determiningGFR as a diagnostic and staging standard for chronic kidney disease（CKD）and its relationship with clinical general characteristic indicators,general biochemical indicators,renal function indicators,chronic medical history,and damage to heart and carotid target organs;3.Explore the significance of Gates method in the determination of split renal GFR as a preoperative routine examination of one side kidney/ureteral tumor and the clinical value of asymmetric renal impairment.Methods:1.Retrospective analysis of ^99mTc-DTPA dynamic imaging in the department of nuclear medicine from August 2017 to July 2019,from the whole inspection process,image processing and the reference standard established by Gates method,the influence factors of GFR determined by Gates method were analyzed.Establish standardized quality control system,standardized inspection process and unified image processing.On this basis,the correction equation of Gates method forGFR determination was established according to the reference standard of ^99mTc-DTPA double plasma clearance method widely used in the world.2.The determination of GFR by single or double plasma method of ^99mTc-DTPA was used as the reference standard（rGFR）,the determination of GFR by the Gates method using the correction equation was referred as gGFR,and the CKD-EPI creatinine equations forGFR estimation was referred as eGFR.The bias,accuracy,precision and correlation between gGFR,eGFR and rGFR were compared.According to the diagnosis and staging of CKD in the improved global prognosis of kidney disease（KDIGO）:when GFR<60ml/min/1.73m² and last for more than 3 months,the CKD was diagnosed and classified into five stages based on theGFR value.The diagnosis and staging of CKD by gGFR and eGFR were compared.Clinical data of patients were retrospectively analyzed,the patients were divided into two groups with a boundary of 60ml/min/1.73m² according to gGFR.Statistical analysis was conducted to compare the general characteristic indexes,general biochemical indexes,renal function indexes,chronic medical history,and damage of heart and carotid target organs between the two groups.3.Measures of split renal function:left or right kidney GFR and relative split function percentage of left or right kidney.Left or right kidney GFR=total kidney GFR×relative split function percentage of left or right kidney.The diagnosis of asymmetric renal impairment:the value of the percentage difference in relative split renal function was greater than 10% and theGFR of the total and/or split renal was below the lower limit of the normal reference range for the same age group.A retrospective analysis was performed to determine the incidence,type,degree and influencing factors of asymmetric renal impairment in each population by Gates method of ^99mTc-DTPA renal dynamic imaging in nuclear department.Results:1.A total of 1806 cases of renal dynamic imaging were performed in our department within two years,and the first success rate was 97.7%,the main reason for the failure was that the“bolus”injection was not qualified.Quality control items include pre-examination patient preparation,imaging equipment,imaging agent,full needle collection,injection,image collection,and established a unified implementation standard.The correlation between the measurement of GFR by double plasma method with ^99mTc-DTPA and that by Gates method was statistically significant in 117 patients（r=0.81,P=0.000,95% CI:0.76～0.88）,the correction equation:The corrected GFR=the original GFR×1.122-7.160.2.The bias,precision,15% and 30% accuracy and correlation coefficient of gGFR and rGFR were as follows:-3.83,13.5,77.4%,89.3% and 0.88;these indicators between eGFR and rGFR were as follows:-6.59,26.5,70.2%,79.5% and 0.46.In the 389 cases for CKD diagnosis and staging,the diagnosis of CKD by gGFR was 27% and CKD1～5 phases were 147,137,69,28 and 8 cases respectively,while the diagnosis of CKD by eGFR was 19.5% and CKD1～5 phases were 161,152,52,19 and 5 cases respectively.The Kappa value of CKD staging by gGFR and eGFR was 0.49.In the 274 cases for studying the clinical value of gGFR,the patients were divided into two groups with a boundary of 60ml/min/1.73m² according to gGFR,the age,diastolic blood pressure,fasting blood glucose,triglyceride,HDL cholesterol,very low density lipoprotein cholesterol,atherosclerosis index,creatinine,uric acid and eGFR were significantly different between the two groups（P<0.05）.The proportions of hypertension,diabetes,cardiovascular and cerebrovascular diseases and the history of CKD in the two groups were significantly different（P<0.05）.The ratio of decreased left ventricular systolic/diastolic function and carotid artery stenosis/insufficient blood supply in patients with decreased renal function diagnosed by gGFR was significantly higher than that in patients with normal renal function diagnosed by gGFR（P<0.05）.3.Among the 644 cases renal dynamic imaging,346 had asymmetric renal impairment,with an incidence of 53.7%.The incidence was 47.3% in patients with common chronic diseases and 55.6% in patients with urinary tract diseases.A total of 182 patients underwent renal dynamic imaging examination before operation due to one renal/ureteral tumor,and 105 patients had asymmetric renal impairment,with an incidence of 56.6%,the absolute value of the percentage difference between healthy kidney and affected kidney was（24.1±10.2）%.Conclusions:1.The establishment of standardized inspection process and unified image processing through standardized quality control are the basis to ensure the accuracy of GFR measurement by Gates method.On the basis of quality control,the correction equation was established by using ^99mTc-DTPA double plasma clearance method to determineGFR as the reference standard,which improved the accuracy of GFR determination by Gates method.2.GFR after correction by the Gates method is an accurate measure of renal function.The determination of GFR by Gates method can be used as the basis of diagnosis and staging of CKD.The determination of GFR by Gates method is closely related to clinical biochemical indicators,disease status,and target organ damage.3.^99mTc-DTPA renal dynamic imaging Gates method can accurately determine the left and right renal GFR after correction.The determination of split renal GFR by renal dynamic imaging Gates method is an important basis for the establishment of preoperative surgical program of one renal/ureteral tumor and a reliable and practical examination method for the study of clinical asymmetric renal dysfunction.