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PubMed1975

Validity of corrections for creatinine excretion and creatinine clearance.

Corrections of values for creatinine excretion and creatinine clearance on the basis of body weight reduce the population variation, i.e., narrow the reference range. The range is not further narrowed, however, by correcting for calculated surface area or calculated lean body mass. Corrections of creatinine clearance for body weight and calculated lean body mass remove the sex difference seen in the uncorrected clearances, but creatinine clearance corrected for surface area, although not significantly different between the sexes, give appreciably different reference ranges. These conclusions apply to individuals healthy in terms of body composition.

Adult↗
PubMed2006

[Serum creatinine and creatinine clearance to estimate renal function in essential hypertension].

The shortcoming of serum creatinine (SCr) as an index of renal function is well known, patients can have significantly decreased glomerular filtration rates (GFR) with normal range SCr values, making the recognition of renal dysfunction more difficult. This study was designed to estimate renal function and the prevalence of renal dysfunction in essential hypertensive patients, comparing SCr and 4 formulas used to measure the creatinine clearance (CrCl) (the urinary CrCl formula, Cockcroft-Gault, MDRD and body surface formula) The study included 721 essential hypertensive patients, 319 men (44.2%), 402 women (55.8%), mean age 56.3 +/- 13.9 (53.7 +/- 14.4 vs 58.3 +/- 13.3). In all subjects SCr was measured and 24-h urine sample was collected to evaluate CrCl. Creatinine clereance was calculated by 4 formulas. Patients were grouped according to age (< 40, 41-65, 65-75 and > 76) and renal function was classified as normal when SCr < 1.4 in women and 1.5 mg/dl in men and CrCl (> 60 ml/m, respectively) within the above written formulas. SCr increases with age (1.01 +/- 0.36 vs 1.3 +/- 1.15) and CrCl decreases according to the 4 formulas (107.6; 92.8; 74.7 and 57.3 for the urinary SCr formula); (117.7; 87.7; 65.9 and 49.5 for the CC formula); (87.4, 74.9, 66.5 and 61 for the MDRD formula) and (97, 85.3, 71.9 and 57.3 for the body suface formula). The 4 formulas are comparable markers of renal function in the overall population. With any formula the percentage of patients with impaired renal function was much higher than indicated by the plasma creatinine alone (4% for SCr) vs 18.3-25.3% (CrCl < 60 ml/m) according to the 4 formulas. This study documents the substantial prevalence of abnormal renal function in essential hypertension. Estimation of GFR may help to facilitate the early identification of patients with renal impairment.

Adolescent↗
PubMed2006

Comparison of estimated glomerular filtration rates from serum creatinine and cystatin C in patients with impaired creatinine production.

Determination of the glomerular filtration rate (GFR) is important for the drug dosage adjustment and clinical management of patients. The aim of our study was the comparison of estimated GFR values from serum creatinine (eGFRcreatinine) and cystatin C (eGFRcystatin C) in patients with impaired creatinine production. A total of 564 serum samples from patients with kidney disease (n=179), liver (n=71) and kidney (n=182) transplants, critically ill patients (n=82) and healthy subjects (n=50) were analyzed for serum creatinine and cystatin C. The creatinine production rate (CPR) was significantly lower in the different groups of patients than in the control group (p<0.001). A negative correlation was found between the eGFRcreatinine/eGFRcystatin C ratio and CPR (r= -0.964, p<0.001). For CPR higher than 800 mg/24h both procedures for estimating the GFR classified values higher and lower than 60 mL/min with an acceptable agreement; however, for CPR less than 800 mg/24h the eGFRcreatinine led to false negatives in a high number of cases with eGFRcystatin C <60 mL/min.

Adult↗
PubMed1980

Colorimetric rate method for the determination of creatinine as implemented by the Beckman Creatinine Analyzer 2.

We evaluated the performance characteristics of the Beckman Creatinine Analyzer 2, a kinetic colorimetric analyzer which utilizes a modified Jaffé reagent. The instrument gave linear measurements to at least 300 mg/L and its within-run precision on a 50 mg/l creatinine standard was 1.1%. Its between-day precision on the 50 mg/L creatinine standard was less than 5.0%. Its results correlated well with those from the manual Jaffé. CentrifiChem System 400, TechniconTM SMATM 6/60 System, and TraceTM systems I and III. Interferences from 19 possible serum constituents and 32 drugs were almost nonexistent. The extended linear range of the Creatinine Analyzer 2 allowed the direct assay of samples from patients undergoing periodic hemodialysis.

Bilirubin↗
PubMed1994

The use of urinary albumin-creatinine ratios and calcium-creatinine ratios as screening tests for pregnancy-induced hypertension.

OBJECTIVE: To assess the potential of both urinary albumin creatinine ratios and urinary calcium-creatinine ratios as screening tests for pregnancy-induced hypertension. METHODS: A prospective, non-interventional study was performed in a teaching hospital antenatal clinic. Five hundred normotensive, nulliparous pregnant women provided a urine sample at 19 weeks' gestation. The main outcome measurements were the development of pregnancy-induced hypertension and preeclampsia. RESULTS: No significant differences in urinary albumin/creatinine and calcium/creatinine were demonstrated between patients who developed pregnancy-induced hypertension and those who remained normotensive. Urinary creatinine concentrations were significantly higher at 19 weeks' gestation in patients who subsequently developed pregnancy-induced hypertension. CONCLUSIONS: This study suggests that neither urinary ratio is a potential screening test for pregnancy-induced hypertension. The increased urinary creatinine concentration in patients who subsequently developed pregnancy-induced hypertension has not previously been reported and merits further investigation.

Adult↗
PubMed1993

Calculation of creatinine clearance from plasma creatinine.

Glomerular filtration rate (GFR) is commonly assessed by measurement of endogenous creatinine clearance (Ccr). Several formulae have been described to calculate Ccr from plasma creatinine. I have evaluated the effectiveness of four formulae in 35 healthy subjects (21M and 14F, 18-34 years) and in 41 patients (24M, 17F, 20-69 years) attending a renal clinic with diminished renal function (serum creatinine 200-600 mumol/l). The GFR was measured using 51 Cr-EDTA clearance and endogenous Ccr. The Ccr was also estimated by four formulae. In healthy subjects Ccr calculated by the formulae of Cockcroft and Gault and Hull et al gave higher correlation coefficient (0.710 and 0.714 respectively) with endogenous Ccr than the formulae of Gates and that of Jellife (0.514 and 0.586 respectively). When all the subjects with a wide range of GFR (3.5-145 mls/min) were considered all the four formulae gave reasonable correlation, but the formula of Cockcroft and Gault was the best. It is recommended that in developing counties with limited resources, the formula of Cockcroft and Gault can be used to estimate Ccr from plasma creatinines.

Adolescent↗
PubMedDate not supplied

Uremia with low serum creatinine-an entity produced by marked creatinine secretion.

Two patients are presented who were uremic requiring dialysis despite steady state serum creatinine levels (Cr) of 4.0 and 4.4 mg percent. Their blood urea nitrogen/creatinine (BUN/Cr) ratios of 54 and 44 were shown to be due to excessive creatinine secretion and urea reabsorption. Evaluation of serum creatinine alone may occasionally give misleading information regarding the level of renal function. If clinical evidence of uremia is present while serum creatinine value is relatively low, measurement of glomerular filtration rate (GFR) by Na-iothalamate 125I (OIT) or inulin is essential.

Aged↗
PubMedDate not supplied

Estimation of total daily creatinine clearance in CAPD from serum creatinine concentration.

OBJECTIVE: To establish whether estimation of creatinine clearance (CrCl) from serum creatinine, gender, age, and weight might reduce the number of 24-hour urine and dialysate collections required to monitor adequacy of delivered dialysis on continuous ambulatory peritoneal dialysis (CAPD). DESIGN: Retrospective single-center study. SETTING: University Hospital. PATIENTS: Creatinine excretion and CrCl were measured in 187 24-hour urine and dialysate collections from 99 CAPD patients (55 male, 44 female). Multiple regression analysis was used to estimate creatinine excretion from age and weight in males and females. CrCl was derived and also calculated using the Cockcroft-Gault and Mitch-Walser formulas. Positive and negative predictive values for indicating adequacy of dialysis were determined. RESULTS: Measured and derived CrCl were correlated (males: r = 0.85; females: r = 0.83; p < 0.001), but agreement was poor (95% limits of agreement: males, 26.05 to -25.75 L/wk; females, 37.47 to -19.49 L/wk). Taking the minimum acceptable CrCl as 60 L/week, the respective positive predictive values of the derived, Cockcroft, and Mitch methods in predicting underdialysis were 88%, 100%, and 100% in males and 88%, 88%, and 89% in females. Negative predictive values were 83%, 57%, and 53% in males and 53%, 48%, and 45% in females. CONCLUSION: A derived CrCl > 60 was not predictive of adequate dialysis. Because the detection of underdialysis is our objective, formal clearance studies should be performed in this group. A derived CrCl < 60 L/wk was predictive of underdialysis in males and females and an increase in dialysis dose without formal clearance measurements could be suggested in these patients. The use of this approach could allow an important reduction in the number of clearance studies required to monitor CAPD adequacy.

Adult↗
PubMed1983

Automated assay of creatinine in serum as simplified by the use of immobilized enzymes, creatinine deiminase, and glutamate dehydrogenase.

A method for the automated analysis of creatinine in serum using immobilized enzymes in column form which does not require a blank correction and can be run in a single buffer of pH 7.5 is described. The method was based on the determination of ammonia formed by the action of creatinine deiminase. Endogenous ammonia in serum was removed by an immobilized glutamate dehydrogenase column prior to the action of creatinine deiminase also immobilized and used in column form. The present method was found to give perfect linearity of the data up to 0.10 g creatinine/liter with satisfactory precision, reproducibility, and accurate reaction recoveries. The immobilized enzyme reactor unit showed good operational stability for a 2-month period, during which time it was repeatedly used for analyses over 2000 times. The results correlated satisfactorily with those obtained by other well-established methods.

Adult↗
PubMed1995

Length/serum creatinine ratio does not predict measured creatinine clearance in critically ill children.

OBJECTIVE: Information regarding renal function is important in critically ill children to adjust the dosage of drugs that are eliminated by the kidneys. Methods for estimating glomerular filtration rate (GFR) based on age and serum creatinine level have shown good agreement with measured creatinine clearance (CLCR) in children without critical illness but have not been examined in critically ill children. METHODS: CLCR (24 hours) was measured (CLCR-measured) in 100 individuals (aged 5.6 years [range, 0.1 to 20.8 years]) admitted to a pediatric intensive care unit. Urine was collected by indwelling bladder catheters. Serum levels were determined. CLCR was calculated (CLCR-measured) according to the standard formula. GFR was estimated (CL-estimated) according to a published method, in which GFR is based on serum creatinine levels, patient length, and a constant that varies with the age and sex of the child. For each patient, the percentage difference between methods was calculated as the difference between the methods divided by the average obtained by the two methods and expressed as a percentage. Bias was calculated as the absolute value of the percentage difference. RESULTS: CLCR-measured and CL-estimated were significantly correlated (CLCR-measured = 0.57 CL-estimated + 16.8; r = 0.68; p < 0.001). However, CL-estimated was greater than CLCR-measured in 84 patients. The difference ranged from -230 to +123 ml/min/1.73 m2 (mean -25.9 ml/min/1.73 m2 [95% confidence interval, -18.1 to 33.7 ml/min/1.73 m2]). The mean percentage difference between the methods was also large (-38.1% [95% confidence interval, -47.1% to 29.2%]) and ranged from -153.2% to 102.1%. The mean bias was 45.2% (95% confidence interval, 37.7% to 52.8%). In 36 of 100 patients the discrepancy between the two methods was greater than 50%. Adjusting for weight percentile, as a proxy for abnormal muscle mass, did not improve the model. CONCLUSION: A method to estimate GFR in children that is based on age and sex, but not critical illness, does not correspond with measured 24-hour CLCR. Use of this method to adjust dosage of drugs eliminated by the kidney might result in significant overdosage in most critically ill children.

Adolescent↗
PubMed2004

A stable three-enzyme creatinine biosensor. 3. Immobilization of creatinine amidohydrolase and sensor development.

We describe the development of an extended use amperometric three-enzyme creatinine biosensor and the successful chemical modification and immobilization of the enzyme creatinine amidohydrolase using polyurethane prepolymers. Creatinine amidohydrolase is significantly stabilized by immobilization in polyurethane polymers. The half-life increases from six to more than 80 days in buffer at 37 degrees C. The effect of silver ions leached from amperometric reference electrodes on enzyme and sensor performance is discussed. The use of cellulose acetate cover membranes to prevent silver from reaching the enzyme is investigated. Sensors prepared with cover membranes have half-lives almost an order of magnitude greater than those prepared with no cover membrane over the silver electrode. The complete biosensor has been constructed on a clinical blood analyzer platform and is stable for many days.

Amidohydrolases↗
PubMed1992

Creatinine arm index as alternative for creatinine height index.

Nutritional assessment of elderly people is limited due to a lack of age-corrected standards. The objective of this study was to develop a new, more age-independent index for nutritional assessment by correcting the creatinine height index (CHI) for the age-induced changes in its variables. This might improve the differentiation between physiological reduction in muscle mass in elderly people and the changes induced by malnutrition. Seventy-four elderly and 100 young healthy volunteers were compared by anthropometric and biochemical-assessment variables. From the high correlation between total arm length and body length (r = 0.86; P less than 0.001) and the use of an alternative formula to calculate ideal body weight (IBW) from height and wrist circumference, a relatively age-independent estimate of IBW was determined. Creatinine arm index, as an adapted index of CHI, is proposed based on this age-independent IBW estimation and a specific creatinine coefficient for different age groups.

Adult↗
PubMed1976

Prediction of creatinine clearance from serum creatinine.

A formula has been developed to predict creatinine clearance (Ccr) from serum creatinine (Scr) in adult males: (see article)(15% less in females). Derivation included the relationship found between age and 24-hour creatinine excretion/kg in 249 patients aged 18-92. Values for Ccr were predicted by this formula and four other methods and the results compared with the means of two 24-hour Ccr's measured in 236 patients. The above formula gave a correlation coefficient between predicted and mean measured Ccr's of 0.83; on average, the difference predicted and mean measured values was no greater than that between paired clearances. Factors for age and body weight must be included for reasonable prediction.

Adolescent↗
PubMed1989

Renal function in the newborn. Newborn creatinine related to birth weight, maturity and maternal creatinine.

The maternal and newborn renal function in 84 normal pregnant women delivering at term was investigated. There was no difference between maternal and newborn plasma concentrations of urea (3.9 +/- 1.0 vs. 3.9 +/- 1.2 mmol/l) and creatinine (65.8 +/- 13.3 vs. 65.3 +/- 11.6 mumols/l). The plasma sodium and potassium concentrations were significantly higher in the newborn (139.6 +/- 4.1 vs. 136.8 +/- 5.1 mmol/l, p less than 0.001, and 5.1 +/- 1.3 vs. 4.2 +/- 0.9 mmol/l, p less than 0.001, respectively). Significant correlations were found between newborn sodium (p less than 0.02) and potassium (p = 0.0001) with maternal potassium concentrations, newborn urea with maternal urea concentrations (p = 0.0001), and newborn creatinine with maternal creatinine concentrations (p = 0.0001), gestation of delivery (p less than 0.05) and birth weight (p = 0.025).

Birth Weight↗
PubMed1986

Renal function in an elderly population. A study of S-creatinine, 51Cr-EDTA clearance, endogenous creatinine clearance and maximal tubular water reabsorption.

There has been reported a decline in renal function with age, a decline that seems to accelerate after the age of 50. A systemically chosen sample of 70- and 75-year-old probands from the study '70-year-olds in Göteborg' have previously been examined with respect to GFR. The present study is a longitudinal follow-up of GFR in the previously examined 75-year-old probands at age 79. Renal tubular water absorption was also determined. In order to make a longitudinal comparison, S-creatinine was determined in a subsample of 166 probands, who had attended the study at 70, 75 and 79 years of age, by using frozen sera from these three examinations. S-creatinine increased slightly but statistically significant in both sexes between 70 years and 79 years of age. The reference values for EDTA clearance at age 79 calculated as M +/- 2 SD were 46-94 ml/min X 1.73 m2 BSA without any difference between the sexes. There was no change in GFR between 75 years and 79 years of age. We did not find any correlation between EDTA clearance and creatinine clearance. The tubular water reabsorption for probands without disorders was 843 +/- 92.6 (range 709-982). The results suggest that the renal filtration rate at age 79 is still good and that the ageing of the tubular function is not as pronounced as that of the GFR.

Age Factors↗
PubMed1988

Evaluation of several creatinine methods in search of a suitable secondary reference method: report from the subcommittee on reference method for creatinine, Nordic Society for Clinical Chemistry.

Several methods for creatinine have been examined by the subcommittee on reference method for creatinine. These include the use of picric acid to precipitate proteins followed by alkalization, or the use of alkaline picrate after protein precipitation and adsorption to Fuller's earth. The first approach was not found to be suitable as a reference method since it was susceptible to matrix effects, fluctuations in temperature and wavelengths. The second approach was less sensitive to these effects but showed variations with different batches of Fuller's earth. The method using high performance liquid chromatography (HPLC) had poor precision, probably because endogenous compounds co-eluted either with creatinine or with the internal standard. The enzymatic method based on the determination of hydrogen peroxide had good accuracy and precision. However, the main disadvantage is that the method is sold as a kit and detailed specifications concerning all the ingredients are not available to permit independent studies using the basic components.

Chromatography, High Pressure Liquid↗
PubMed1976

Reaction of alkaline sodium picrate with creatinine: I. Kinetics and mechanism of formation of the mono-creatinine picric acid complex.

Spectrophotometric, kinetic, and nuclear magnetic resonance studies indicate that alkaline sodium picrate and creatinine react to form a 1/1 aduct between picric and creatinine, with a stability constant of log K= 4.26. Kinetic studies indicate that the forward reaction is first order with respect to picric acid, hydroxide, and creatinine concentration. The reverse reaction, the dissociation of the 1/1 complex, shows a complex dependence on hydroxide concentration. The expression for the observed pseudo-first-order rate constant in the presence of excess picric acid is: Kobsd = K1K0[P][OH] +[K2[OH]x. A value of K1K0 = 5.0 (mol/liter)-2s-1 is obtained. For accurate analytical results with this reaction, hydroxide concentration must be maintained at a constant value for both samples and standards.

Chemical Phenomena↗