Acute kidney injury (AKI) and chronic kidney disease (CKD) are major health problems. Urinary biomarkers have both diagnostic and prognostic utility in AKI and CKD. However, how biomarker excretion rates should be reported, especially whether they should be normalised to urinary creatinine concentration (uCr), is controversial. Some studies suggest that normalisation to uCr may be inappropriate at times, as urinary creatinine excretion rate may vary greatly, depending on the situation. Notably, recent studies suggest that while normalisation of values to UCr may be valid for the evaluation of CKD and prediction of AKI sequelae and occurrences, it could be inappropriate for the diagnosis of AKI, or in the presence of certain acute kidney disease states.
Acute Kidney Injury ; urine ; Biomarkers ; urine ; Creatinine ; urine ; Glomerular Filtration Rate ; Humans ; Kidney ; physiopathology ; Nephrology ; methods ; standards ; Renal Insufficiency, Chronic ; urine ; Treatment Outcome ; Urinalysis ; standards

INTRODUCTIONClinical 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.

METHODSSerum 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.

RESULTSThe 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.

CONCLUSIONThe 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.

Adult ; Aged ; Body Mass Index ; China ; ethnology ; Female ; Healthy Volunteers ; Hospitals, University ; Humans ; Hypertension ; epidemiology ; India ; ethnology ; Linear Models ; Malaysia ; ethnology ; Male ; Middle Aged ; Prospective Studies ; Renal Insufficiency, Chronic ; ethnology ; urine ; Sodium, Dietary ; urine

INTRODUCTIONClinical practice guidelines recommend different levels of dietary protein intake in predialysis chronic kidney disease (CKD) patients. It is unknown how effectively these recommendations perform in a multi-ethnic Asian population, with varied cultural beliefs and diets. We assess the profi le of protein intake in a multi-ethnic Asian population, comparing healthy participants and CKD patients.

MATERIALS AND METHODSWe analysed the 24-hour urine collections of the Asian Kidney Disease Study (AKDS) and the Singapore Kidney Function Study (SKFS) to estimate total protein intake (TPI; g/day). We calculated ideal body weight (IDW; kg): 22.99 × height2 (m). Standard statistical tests were applied where appropriate, and linear regression was used to assess associations of continuous variables with protein intake.

RESULTSThere were 232 CKD patients and 103 healthy participants with 35.5% diabetics. The mean TPI in healthy participants was 58.89 ± 18.42 and the mean TPI in CKD patients was 53.64 ± 19.39. By US National Kidney Foundation (NKF) guidelines, 29/232 (12.5%) of CKD patients with measured glomerular filtration rate (GFR) <25 (in mL/min/1.73 m2) had a TPI-IDW of <0.6 g/kg/day. By Caring for Australasians with Renal Impairment (CARI) guidelines, 76.3% (177/232) of CKD patients had TPI-IDW >0.75g/kg/ day. By American Dietetic Association (ADA) guidelines, 34.7% (44/127) of CKD patients with GFR <50 had TPI-IDW between 0.6 to 0.8 g/kg/day. Only 1/6 non-diabetic CKD patients with GFR <20 had a protein intake of between 0.3 to 0.5 g/kg/day. A total of 21.9% (25/114) of diabetic CKD patients had protein intake between 0.8 to 0.9 g/kg/day.

CONCLUSIONOn average, the protein intake of most CKD patients exceeds the recommendations of guidelines. Diabetic CKD patients should aim to have higher protein intakes.

Adult ; Aged ; Asian Continental Ancestry Group ; Cross-Sectional Studies ; Dietary Proteins ; administration & dosage ; urine ; Female ; Health Surveys ; Humans ; Malnutrition ; ethnology ; Middle Aged ; Renal Insufficiency, Chronic ; ethnology ; Singapore

INTRODUCTIONClinical 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.

METHODSSerum 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.

RESULTSThe 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.

CONCLUSIONThe 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.

Adult ; Aged ; Biomarkers ; blood ; urine ; China ; ethnology ; Creatinine ; blood ; Cystatin C ; blood ; Female ; Glomerular Filtration Rate ; Healthy Volunteers ; Humans ; India ; ethnology ; Malaysia ; ethnology ; Male ; Middle Aged ; Models, Statistical ; Prospective Studies ; Renal Insufficiency, Chronic ; blood ; urine ; Reproducibility of Results