Kunihiro Yamagata

Revised Equations for Estimated GFR From Serum Creatinine in Japan

BACKGROUND Estimation of glomerular filtration rate (GFR) is limited by differences in creatinine generation among ethnicities. Our previously reported GFR-estimating equations for Japanese had limitations because all participants had a GFR less than 90 mL/min/1.73 m2 and serum creatinine was assayed in different laboratories. STUDY DESIGN Diagnostic test study using a prospective cross-sectional design. New equations were developed in 413 participants and validated in 350 participants. All samples were assayed in a central laboratory. SETTING & PARTICIPANTS Hospitalized Japanese patients in 80 medical centers. Patients had not participated in the previous study. REFERENCE TEST Measured GFR (mGFR) computed from inulin clearance. INDEX TEST Estimated GFR (eGFR) by using the modified isotope dilution mass spectrometry (IDMS)-traceable 4-variable Modification of Diet in Renal Disease (MDRD) Study equation using the previous Japanese Society of Nephrology Chronic Kidney Disease Initiative (JSN-CKDI) coefficient of 0.741 (equation 1), the previous JSN-CKDI equation (equation 2), and new equations derived in the development data set: modified MDRD Study using a new Japanese coefficient (equation 3), and a 3-variable Japanese equation (equation 4). MEASUREMENTS Performance of equations was assessed by means of bias (eGFR - mGFR), accuracy (percentage of estimates within 15% or 30% of mGFR), root mean squared error, and correlation coefficient. RESULTS In the development data set, the new Japanese coefficient was 0.808 (95% confidence interval, 0.728 to 0.829) for the IDMS-MDRD Study equation (equation 3), and the 3-variable Japanese equation (equation 4) was eGFR (mL/min/1.73 m2) = 194 x Serum creatinine(-1.094) x Age(-0.287) x 0.739 (if female). In the validation data set, bias was -1.3 +/- 19.4 versus -5.9 +/- 19.0 mL/min/1.73 m2 (P = 0.002), and accuracy within 30% of mGFR was 73% versus 72% (P = 0.6) for equation 3 versus equation 1 and -2.1 +/- 19.0 versus -7.9 +/- 18.7 mL/min/1.73 m(2) (P < 0.001) and 75% versus 73% (P = 0.06) for equation 4 versus equation 2 (P = 0.06), respectively. LIMITATION Most study participants had chronic kidney disease, and some may have had changing GFRs. CONCLUSION The new Japanese coefficient for the modified IDMS-MDRD Study equation and the new Japanese equation are more accurate for the Japanese population than the previously reported equations.

Original InvestigationPathogenesis and Treatment of Kidney DiseaseRevised Equations for Estimated GFR From Serum Creatinine in Japan

BACKGROUND Estimation of glomerular filtration rate (GFR) is limited by differences in creatinine generation among ethnicities. Our previously reported GFR-estimating equations for Japanese had limitations because all participants had a GFR less than 90 mL/min/1.73 m2 and serum creatinine was assayed in different laboratories. STUDY DESIGN Diagnostic test study using a prospective cross-sectional design. New equations were developed in 413 participants and validated in 350 participants. All samples were assayed in a central laboratory. SETTING & PARTICIPANTS Hospitalized Japanese patients in 80 medical centers. Patients had not participated in the previous study. REFERENCE TEST Measured GFR (mGFR) computed from inulin clearance. INDEX TEST Estimated GFR (eGFR) by using the modified isotope dilution mass spectrometry (IDMS)-traceable 4-variable Modification of Diet in Renal Disease (MDRD) Study equation using the previous Japanese Society of Nephrology Chronic Kidney Disease Initiative (JSN-CKDI) coefficient of 0.741 (equation 1), the previous JSN-CKDI equation (equation 2), and new equations derived in the development data set: modified MDRD Study using a new Japanese coefficient (equation 3), and a 3-variable Japanese equation (equation 4). MEASUREMENTS Performance of equations was assessed by means of bias (eGFR - mGFR), accuracy (percentage of estimates within 15% or 30% of mGFR), root mean squared error, and correlation coefficient. RESULTS In the development data set, the new Japanese coefficient was 0.808 (95% confidence interval, 0.728 to 0.829) for the IDMS-MDRD Study equation (equation 3), and the 3-variable Japanese equation (equation 4) was eGFR (mL/min/1.73 m2) = 194 x Serum creatinine(-1.094) x Age(-0.287) x 0.739 (if female). In the validation data set, bias was -1.3 +/- 19.4 versus -5.9 +/- 19.0 mL/min/1.73 m2 (P = 0.002), and accuracy within 30% of mGFR was 73% versus 72% (P = 0.6) for equation 3 versus equation 1 and -2.1 +/- 19.0 versus -7.9 +/- 18.7 mL/min/1.73 m(2) (P < 0.001) and 75% versus 73% (P = 0.06) for equation 4 versus equation 2 (P = 0.06), respectively. LIMITATION Most study participants had chronic kidney disease, and some may have had changing GFRs. CONCLUSION The new Japanese coefficient for the modified IDMS-MDRD Study equation and the new Japanese equation are more accurate for the Japanese population than the previously reported equations.

Overview of Regular Dialysis Treatment in Japan (as of 31 December 2008)

A nationwide statistical survey of 4124 dialysis facilities was conducted at the end of 2008 and 4081 facilities (99.0%) responded. The number of patients undergoing dialysis at the end of 2008 was determined to be 283 421, an increase of 8179 patients (3.0%) compared with that at the end of 2007. The number of dialysis patients per million at the end of 2008 was 2220. The crude death rate of dialysis patients from the end of 2007 to the end of 2008 was 9.8%. The mean age of the new patients begun on dialysis was 67.2 years and the mean age of the entire dialysis patient population was 65.3 years. For the primary diseases of the new patients begun on dialysis, the percentages of patients with diabetic nephropathy and chronic glomerulonephritis were 43.3% and 22.8%, respectively. Among the facilities that measured bacterial count in the dialysate solution in 2008, 52.0% of facilities ensured that a minimum dialysate solution volume of 10 mL was sampled. Among the patients treated by facility dialysis, 95.4% of patients were treated three times a week, and the average time required for one treatment was 3.92 ± 0.53 (SD) h. The average amounts of blood flow and dialysate solution flow were 197 ± 31 and 487 ± 33 mL/min, respectively. The number of patients using a polysulfone membrane dialyzer was the largest (50.7%) and the average membrane area was 1.63 ± 0.35 m2. According to the classification of dialyzers by function, the number of patients using a type IV dialyzer was the largest (80.3%). The average concentrations of each electrolyte before treatment in patients treated with blood purification by extracorporeal circulation were 138.8 ± 3.3 mEq/L for serum sodium, 4.96 ± 0.81 mEq/L for serum potassium, 102.1 ± 3.1 mEq/L for serum chloride, and 20.7 ± 3.0 mEq/L for HCO3‐; the average serum pH was 7.35 ± 0.05. Regarding the type of vascular access in patients treated by facility dialysis, in 89.7% of patients an arteriovenous fistula was used and in 7.1% an arteriovenous graft was used. The percentage of hepatitis C virus (HCV)‐positive patients who were HCV‐negative in 2007 was 1.04%; the percentage is particularly high in patients with a period of dialysis of 20 years or longer. The risk of becoming HCV‐positive was high in patients with low serum creatinine, serum albumin, and serum total cholesterol levels, and/or a low body mass index before beginning dialysis.

Estimation of glomerular filtration rate by the MDRD study equation modified for Japanese patients with chronic kidney disease

BackgroundAccurate estimation of the glomerular filtration rate (GFR) is crucial for the detection of chronic kidney disease (CKD). In clinical practice, GFR is estimated from serum creatinine using the Modification of Diet in Renal Disease (MDRD) study equation or the Cockcroft-Gault (CG) equation instead of the time-consuming method of measured clearance for exogenous markers such as inulin. In the present study, the equations originally developed for a Caucasian population were tested in Japanese CKD patients, and modified with the Japanese coefficient determined by the data.MethodsThe abbreviated MDRD study and CG equations were tested in 248 Japanese CKD patients and compared with measured inulin clearance (Cin) and estimated GFR (eGFR). The Japanese coefficient was determined by minimizing the sum of squared errors between eGFR and Cin. Serum creatinine values of the enzyme method in the present study were calibrated to values of the noncompensated Jaffé method by adding 0.207 mg/dl, because the original MDRD study equation was determined by the data for serum creatinine values measured by the noncompensated Jaffé method. The abbreviated MDRD study equation modified with the Japanese coefficient was validated in another set of 269 CKD patients.ResultsThere was a significant discrepancy between measured Cin and eGFR by the 1.0 × MDRD or CG equations. The MDRD study equation modified with the Japanese coefficient (0.881 × MDRD) determined for Japanese CKD patients yielded lower mean difference and higher accuracy for GFR estimation. In particular, in Cin 30–59 ml/min per 1.73 m2, the mean difference was significantly smaller with the 0.881 × MDRD equation than that with the 1.0 × MDRD study equation (1.9 vs 7.9 ml/min per 1.73 m2; P <?0.01), and the accuracy was significantly higher, with 60% vs 39% of the points deviating within 15%, and 97% vs 87% of points within 50%, respectively (both P <?0.01). Validation with the different data set showed the correlation between eGFR and Cin was better with the 0.881 × MDRD equation than with the 1.0 × MDRD study equation. In Cin less than 60 ml/min per 1.73 m2, the accuracy was significantly higher, with 85% vs 69% of the points deviating within 50% (P <?0.01), respectively. The mean difference was also significantly smaller (P <?0.01). However, GFR values calculated by the 0.881 × MDRD equation were still underestimated in the range of Cin over 60 ml/min per 1.73 m2.ConclusionsAlthough the Japanese coefficient improves the accuracy of GFR estimation of the original MDRD study equation, a new equation is needed for more accurate estimation of GFR in Japanese patients with CKD stages 3 and 4.

Prevalence of chronic kidney disease (CKD) in the Japanese general population predicted by the MDRD equation modified by a Japanese coefficient

BackgroundThe number of patients with end-stage renal disease (ESRD) in Japan has continuously increased in the past three decades. In 2005, 36 063 patients whose average age was 66 years entered a new dialysis program. This large number of ESRD patients could be just the tip of the iceberg of an increasing number of patients with chronic kidney disease (CKD). However, to date, a nationwide epidemiological study has not been conducted yet to survey the CKD population.MethodsData for 527 594 (male, 211 034; female, 316 560) participants were obtained from the general adult population aged over 20 years who received annual health check programs in 2000–2004, from seven different prefectures in Japan: Hokkaido, Fukushima, Ibaraki, Tokyo, Osaka, Fukuoka, and Okinawa prefectures. The glomerular filtration rate (GFR) for each participant was estimated from the serum creatinine values, using the abbreviated Modification of Diet in Renal Disease (MDRD) study equation modified by the Japanese coefficient.ResultsThe prevalences of CKD stage 3 in the study population, stratified by age groups of 20–29, 30–39, 40–49, 50–59, 60–69, 70–79, and 80–89 years, were 1.4%, 3.6%, 10.8%, 15.9%, 31.8%, 44.0%, and 59.1%, respectively, predicting 19.1 million patients with stage 3 CKD in the Japanese general adult population of 103.2 million in 2004. CKD stage 4 + 5 was predicted in 200 000 patients in the Japanese general adult population. Comorbidity of hypertension, diabetes, and proteinuria increased as the estimated GFR (eGFR) decreased. The prevalence of concurrent CKD was significantly higher in hypertensive and diabetic populations than in the study population overall when CKD was defined as being present with an eGFR of less than 40 ml/min per 1.73 m2 instead of less than 60 ml/min per 1.73 m2.ConclusionsAbout 20% of the Japanese adult population (i.e., approximately 19 million people) are predicted to have stage 3 to 5 CKD, as defined by a GFR of less than 60 ml/min per 1.73 m2.

Slower Decline of Glomerular Filtration Rate in the Japanese General Population: A Longitudinal 10-Year Follow-Up Study

The prevalence of stage 3 to 5 chronic kidney disease (CKD) in Japan (18.7%) is considerably higher than that in the United States (4.5%). This study investigated in the Japanese general population whether this higher prevalence of CKD might reflect to a progressive decline of renal function, and in turn to the increased risk of end-stage renal disease. A decline in renal function over 10 years was examined in 120,727 individuals aged 40 years or older who participated in the annual health examination program of the two periods over 10 years, 1988–1993 and 1998–2003. Renal function was assessed with estimated glomerular filtration rate (GFR) using the abbreviated Modification of Diet in Renal Disease (MDRD) Study equation modified by a Japanese coefficient. The rate of GFR decline in the participants was 0.36 mL/min/1.73 m2/year on average. In the male population aged 50–79, the mean rate of GFR decline was significantly higher in the presence of hypertension than in its absence. The rate of GFR decline was more than two times higher in participants with proteinuria than in those without proteinuria in both sexes. The rate was significantly higher in participants with an initial GFR <50 mL/min/1.73 m2 among the groups younger than age 70 and in participants with an initial GFR <40 mL/min/1.73 m2 in the group with age 70–79. Based on the slow rate of GFR decline, we concluded that the decline in renal function progresses slowly in the Japanese general population. Hypertension, proteinuria and lower GFR were found to be significant risk factors for a faster decline of GFR.

Laser microdissection-based analysis of cytokine balance in the kidneys of patients with lupus nephritis

To determine the cytokine balance in patients with lupus nephritis (LN), we analysed kidney‐infiltrating T cells. Renal biopsy samples from 15 systemic lupus erythematosus (SLE) patients were used. In accordance with the classification of International Society of Nephrology/Renal Pathology Society, they were categorized into Class III, Class III+V (Class III‐predominant group, n = 4), Class IV, Class IV+V (Class IV‐predominant group, n = 7) and Class V (n = 4) groups. The single‐cell samples of both the glomelular and interstitial infiltrating cells were captured by laser‐microdissection. The glomerular and interstitial infiltrating T cells produced interleukin (IL)‐2, IL‐4, IL‐10, IL‐13 and IL‐17 cytokines in the Class III‐predominant, Class IV‐predominant and Class V groups. Interferon‐gamma was detected only in the glomeruli of the Class III‐predominant and Class V group samples. The expression level of IL‐17 was correlated closely with clinical parameters such as haematuria, blood urea nitrogen level, SLE Disease Activity Index scores in both glomeruli and interstitium, urine protein level in glomeruli and serum creatinine and creatinine clearance levels in interstitium. This suggests that the glomerular infiltrating T cells might act as T helper type 1 (Th1), Th2 and Th17 cells while the interstitial infiltrating T cells, act as Th2 and Th17 cells in the Class III‐predominant and Class V groups. In contrast, both the glomerular and interstitial infiltrating T cells might act as Th2 and Th17 cells in the Class IV‐predominant group. The cytokine balances may be dependent upon the classification of renal pathology, and IL‐17 might play a critical role in SLE development.

An Overview of Regular Dialysis Treatment in Japan (As of 31 December 2010)

A nationwide statistical survey of 4226 dialysis facilities was conducted at the end of 2010, and 4166 facilities (98.6%) responded. The number of new patients introduced into dialysis was 37 512 in 2010. This number has decreased for two consecutive years since it peaked in 2008. The number of patients who died in 2010 was 28 882, which has been increasing every year. The number of patients undergoing dialysis at the end of 2010 was 298 252, which is an increase of 7591 (2.6%) compared with that at the end of 2009. The number of dialysis patients per million at the end of 2010 was 2329.1. The crude death rate of dialysis patients in 2010 was 9.8%, and has been gradually increasing. The mean age of the new patients introduced into dialysis was 67.8 years and the mean age of the entire dialysis patient population was 66.2 years. Regarding the primary disease of the new patients introduced into dialysis, the percentage of patients with diabetic nephropathy was 43.6%, which is a slight decrease from that in the previous year (44.5%). Patients with diabetic nephropathy as the primary disease accounted for 35.9% of the entire dialysis patient population, which approaches the percentage of patients with chronic glomerulonephritis as the primary disease (36.2%). The percentage of patients who had undergone carpal tunnel release surgery (CTx) was 4.3%, which is a slight decrease from that at the end of 1999 (5.5%). The decrease in the percentage of patients who had undergone CTx was significant among the patients with dialysis durations of 20–24 years (1999, 48.0%; 2010, 23.2%). A total weekly Kt/V attributable to peritoneal dialysis and their residual functional kidney was 1.7 or higher for 59.4% of patients who underwent peritoneal dialysis.

An Overview of Regular Dialysis Treatment in Japan (as of 31 December 2012)

A nationwide statistical survey of 4279 dialysis facilities was conducted at the end of 2012, among which 4238 responded (99.0%). The number of new dialysis patients was 38 055 in 2012. Since 2008, the number of new dialysis patients has remained almost the same without any marked increase or decrease. The number of dialysis patients who died in 2012 was 30 710; a slight decrease from 2011 (30 743). The dialysis patient population has been growing every year in Japan; it was 310 007 at the end of 2012, which exceeded 310 000 for the first time. The number of dialysis patients per million at the end of 2012 was 2431.2. The crude death rate of dialysis patients in 2012 was 10.0%, a slight decrease from that in 2011 (10.2%). The mean age of new dialysis patients was 68.5 years and the mean age of the entire dialysis patient population was 66.9 years. The most common primary cause of renal failure among new dialysis patients was diabetic nephropathy (44.2%). The actual number of new dialysis patients with diabetic nephropathy has been approximately 16 000 for the last few years. Diabetic nephropathy was also the most common primary disease among the entire dialysis patient population (37.1%), followed by chronic glomerulonephritis (33.6%). The percentage of dialysis patients with diabetic nephropathy has been continuously increasing, whereas not only the percentage but also the actual number of dialysis patients with chronic glomerulonephritis has decreased. The number of patients who underwent hemodiafiltration (HDF) at the end of 2012 was 21 725, a marked increase from that in 2011 (14 115). In particular, the number of patients who underwent on‐line HDF increased threefold from 4890 in 2011 to 14 069 in 2012. From the results of the facility survey, the number of patients who underwent peritoneal dialysis (PD) was 9514 and that of patients who did not undergo PD despite having a PD catheter in the abdominal cavity was 347. From the results of the patient survey, among the PD patients, 1932 also underwent another dialysis method using extracorporeal circulation, such as hemodialysis (HD) and HDF. The number of patients who underwent HD at home in 2012 was 393, a marked increase from that in 2011 (327).

An overview of regular dialysis treatment in Japan (as of 31 December 2007).

A nationwide statistical survey of 4098 dialysis facilities was conducted at the end of 2007, and 4052 facilities (98.88%) participated. The number of patients undergoing dialysis at the end of 2007 was determined to be 275 242, an increase of 10 769 patients (4.1%) compared with that at the end of 2006.The number of dialysis patients per million at the end of 2007 was 2154. The crude death rate of dialysis patients at the end of 2007 from the end of 2006 was 9.4%. The mean age of new patients begun on dialysis was 66.8 years and the mean age of the entire dialysis patient population was 64.9 years. For the primary diseases of new patients begun on dialysis, the percentages of patients with diabetic nephropathy and chronic glomerulonephritis were 43.4% and 23.8%, respectively. The percentages of facilities that achieved the control standard of endotoxin concentration in the dialysate solution of <0.05 EU/mL and those that achieved a bacterial count of <100 cfu/mL in the dialysate solution, as specified by the Japanese Society for Dialysis Therapy, were 93.6% and 97.4%, respectively. The percentage of patients positive for the hepatitis C virus antibody among the entire dialysis population significantly decreased from 15.95% at the end of 1999 to 9.83% at the end of 2007. The mean hemoglobin concentration in all the dialysis patients at the end of 2007 was 10.27 (±1.32, SD) g/dL, which has scarcely changed over the last three years. The numbers of male and female patients with a history of hip fracture were 142.9 and 339.0 per 10 000 dialysis patients, respectively, showing an extremely high prevalence among female patients. A history of hip fracture correlates with a low body mass index, serum albumin concentration, and a history of diabetes. The serum creatinine level of patients upon introduction to dialysis was 8.34 (±3.55) mg/dL, and the estimated glomerular filtration rate was 5.43 (±3.43) mL/min/1.73 m2 for the patients who were newly begun on dialysis in 2007.