Glomerular filtration rates in healthy Asians without kidney disease.

AIM: The Chronic Kidney Disease Collaboration - Epidemiology (CKD-EPI) glomerular filtration rates (GFR) estimation equation is believed to estimate GFR more accurately in healthy people but this has not been validated in Asians. We studied the distribution of GFR in a multi-ethnic Asian population without CKD, and compared the performance of measures of GFR estimation, including the CKD-EPI equation, Cockroft-Gault equation, and 24-hour urine creatinine clearances. MATERIALS AND METHODS: A total of 103 healthy volunteers without a history of kidney disease, hypertension, or diabetes underwent GFR measurement using 3-sample plasma clearance of (99m) Tc-DTPA. Cockroft-Gault estimated GFR and 24-hour urine creatinine clearances were normalized to body surface area. RESULTS: The mean measured GFR was 101 ± 15.8 mL/min per 1.73 m(2) and was lowest in Indians (93 ± 12.3 mL/min per 1.73 m(2); P < 0.001). The CKD-EPI equation appears to be more accurate for healthy participants. Estimated GFR correlated with measured GFR (r = 0.57, P < 0.001), and the mean difference is 3.72 ± 14.43 mL/min per 1.73 m(2) (P < 0.001). However, estimating GFR using self-directed 24-hour urine creatinine clearances is poorer than using the CKD-EPI equation. CONCLUSIONS: GFR estimation using self-directed 24-hour urine collection for creatinine clearance is less accurate than using the CKD-EPI equation. A larger study is required to clarify GFR in healthy Asians, and the association of health outcomes of Asian kidney donors with lower GFR thresholds.

Performance of the CKD-EPI creatinine-cystatin C glomerular filtration rate estimation equations in a multiethnic Asian population.

INTRODUCTION: Clinical practice guidelines recommend using creatinine-based equations to estimate glomerular filtration rates (GFRs). While these equations were formulated for Caucasian-American populations and have adjustment coefficients for African-American populations, they are not validated for other ethnicities. The Chronic Kidney Disease-Epidemiology Collaborative Group (CKD-EPI) recently developed a new equation that uses both creatinine and cystatin C. We aimed to assess the accuracy of this equation in estimating the GFRs of participants (healthy and with chronic kidney disease [CKD]) from a multiethnic Asian population. METHODS: Serum samples from the Asian Kidney Disease Study and the Singapore Kidney Function Study were used. GFR was measured using plasma clearance of 99mTc-DTPA. GFR was estimated using the CKD-EPI equations. The performance of GFR estimation equations were examined using median and interquartile range values, and the percentage difference from the measured GFR. RESULTS: The study comprised 335 participants (69.3% with CKD; 38.5% Chinese, 29.6% Malays, 23.6% Indians, 8.3% others), with a mean age of 53.5 ± 15.1 years. Mean standardised serum creatinine was 127 ± 86 µmol/L, while mean standardised serum cystatin C and mean measured GFR were 1.43 ± 0.74 mg/L and 67 ± 33 mL/min/1.73 m2, respectively. The creatinine-cystatin C CKD-EPI equation performed the best, with an estimated GFR of 67 ± 35 mL/min/1.73 m2. CONCLUSION: The new creatinine-cystatin C equation estimated GFR with little bias, and had increased precision and accuracy in our multiethnic Asian population. This two-biomarker equation may increase the accuracy of population studies on CKD, without the need to consider ethnicity.

Spot urine tests in predicting 24-hour urine sodium excretion in Asian patients.

OBJECTIVE: The control of hypertension is often suboptimal, and it is frequently due to excessive sodium intake. Monitoring sodium intake is cumbersome and involves 24-hour collection of urine. We hypothesize that a spot urine test can accurately predict 24-hour urine sodium excretion in an Asian population. DESIGN: This is a prospective, observational study. We used stored urine specimens (n = 333) from the Asian Kidney Disease Study and Singapore Kidney Function Study Phase I. We measured spot urine tests and correlated these variables to the previously measured 24-hour urine sodium measurements. RESULTS: Age, gender, ethnicity, diastolic blood pressure, height, weight, body mass index, serum creatinine, spot urine sodium, spot urine chloride, and spot urine osmolality were associated with 24-hour urine sodium excretion. The final model for predicting 24-hour urine sodium less than 100 mmol included age, gender, ethnicity, weight, and spot urine sodium. CONCLUSION: Spot urine sodium can help monitor a patient's sodium intake when used in the derived 5-variable equation.