Creatinine measurement

Obtain a baseline serum creatinine measurement. Calculate the estimated creatinine clearance and adjust the dose of H2RAs and sucralfate according to package insert recommendations. 

Drugs cleared by the renal route often require adjustment of clearance in proportion to renal function. This can be conveniently estimated from the creatinine clearance, calculated from a single serum creatinine measurement and the predicted creatinine production rate. 

External standard procedure using ChromStar software or manual calculation using an integrator. Measure the creatinine in urine and calculate the results as mmol/mol creatinine. Measure Hb in dried blood extracts and calculate results as nmol/g Hb. 

A commonly used surrogate marker for actual creatinine clearance is the Cockcroft-Gault formula, which employs creatinine measurements and a patient s age and weight to predict the clearance. It is named after the scientists who first published the formula. The equation is popular because it is easy to calculate. 

Wang TL, Chiang HK, Lu HH, Peng EY (2005) Semi-quantitative surface enhanced Raman scattering spectroscopic creatinine measurement in human urine samples. Opt Quant Electron... 

The data in Tables 4,3,4,4, and 4,5 illustrate the broad applicability of urinary creatinine measurements in the I lUtritional sciences. These studies concern the excretion of urinary nitrogen (Table 4.3), calcium (Table 4.4), and riboflavin (Table... 

In all crises, the amount of metabolite is expressed per nfiilligram of creatinine excreted, rather than on a "per-volume" or "per-day" basis. Another reason for expressing excretion data in terms of creatinine is that, although a researcher might want to determine excretion data on a per-day basis, collection of an entire day s urinary output may be difficult or inconvenient. This difficulty can be overcome by using creatinine measurements. 

WaiserM. Assessing renai function from creatinine measurements in aduits with chronic renai faiiure. Am J Kidney Dis 1998 32 23-31. 

Zoledronic acid has also been investigated in the prevention of cancer treatment-induced bone loss in 401 premenopausal women receiving adjuvant endocrine therapy for hormone-responsive breast cancer in a randomised, open-label. Phase 111 clinical trial [76]. In this study, patients received tamoxifen and goserelin with or without zoledronic acid (4 mg i.v. every 6 months) versus anastrozole and goserelin with or without zoledronic acid (4 mg i.v. every 6 months) for 3 years. The combination of zoledronic acid with endocrine therapy was well tolerated and was not associated with changes in renal function in this patient population. Over 3 years, 2, 904 serum creatinine measurements were taken, the mean serum creatinine level was 0.78 + 0.17 mg/ dl, and no patient had serum creahnine levels that exceeded 1.5 times the upper limit of normal [76]. 

Urine creatinine is used to adjust the values of urinary biological indicators for example, creatinine measurements are necessary for correction of vanilmandelic and homovanillic acids, which indicate neuroblastoma and pheochromocytoma, when excreted in urine in abnormally increased concentrations. Ratios of vanilmandelic and homovanillic acids to creatinine have been utilized as a diagnostic index of these diseases. 

E369 Nanji, A.A., Poon, R. and Hinberg, I. (1987). Interference by cephalosporins with creatinine measurement by desk-top analyzers. Europ. J. Clin. Pharmacol. 33, 427-429. 

Lidocaine metabolite and creatinine measurement in the Ektachem 700 Steps to minimize its impact on patient care. Clin. Chem. 34, 2144-2148. 

E698 Franzini, C., Morelli, A.M. and Cattozzo, G. (1991). Use of a synthetic soluble bilirubin derivative to assess interference in creatinine measurements. Clin. Chem. 37, 236-238. 

The clinical utility of creatinine measurement is discussed later in this chapter. 

Clearly, standardization of creatinine measurement is crucial to the ability to accurately diagnose, stage, and manage CKD. Further, it is a prerequisite to the meaningful... 

Given the discussion above, reference intervals for plasma creatinine are clearly method dependent. Typically, reference intervals for plasma creatinine, measured by Jaffe methods, are 0.9 to 1,3 mg/dL (80 to 115 p,mol/L) in men and 0.6 to 1.1 mg/dL (53 to 97p.mol/L) in women. Plasma creatinine concentration in patients with untreated end-stage renal disease (ESRD) may exceed 11 mg/dL (lOOOlxmol/L). Reference intervals for plasma creatinine are also listed in Chapter 56. 

Plasma creatinine is an imperfect marker of GFR and therefore it is not altogether surprising that formulas based predommantly upon it are imperfect. Their use cannot circumvent the very significant spectral interferences affecting plasma creatinine measurement (i.e., hemolysis, icterus, and lipemia) and the formulas are unsuitable for use in patients with acute renal failure, in whom plasma creatinine concentrations are changing rapidly. Additionally, the formulas are critically susceptible to variations in creatinine assay calibration and specificity. Notwithstanding the MDRD formula is thought to improve the estimation of GFR compared with plasma creatinine alone. 

Carobene A, Ferrero C, Ceriotti F, Modenese A, Besozzi M, et al. Creatinine measurement proficiency testing assignment of matrix-adjusted ID GC-MS target values. CUn Chem 1997 43 1342-7. 

Rowe DJ, Omar H, Barratt SL, Biggs P. An evaluation of blood creatinine measurement by creatinase on the NOVA M7 blood gas analyser. Clin Chim Acta 2001 307 23-5. 

Concentrations of urinary resorption markers are usually normalized by dividing by the urinary creatinine concentration. The variability (within- and between-method) of creatinine measurements, within-subject variability in urinary creatinine, and creatinine s dependence on muscle mass contribute to the overall variability of urinary resorption markers. 

Studies comparing the Schwartz-predicted GFR versus measured GFR noted that the Schwartz formula overestimated GFR in patients with decreasing GFR. The formula may not provide an accurate estimation of GFR in patients with rapidly changing serum creatinine concentrations, as seen in the critical care setting, in infants younger than 1 week of age, and in patients with obesity, malnutrition, or muscle wasting. Factors that interfere with serum creatinine measurement also may cause errors in estimation of GFR. 

Administration of cimetidine has also resulted in improved performance of CG to predict GFR. Ixkes and associates gave patients three 800-mg doses of cimetidine in 24 hours, and measured creatinine plasma levels from 3 to 7 hours following the final dose. During this 4-hour period, the CL iothalamate was used to measure the GFR. The CG calculations were performed with the plasma creatinine measurement 3 hours after the last dose of cimetidine. The ratio of the CG-estimated CLcriCL iothalamate decreased from 1.28 0.21 to 0.98 0.11 in the presence of cimetidine. 

Walser M. Assessing renal function from creatinine measurements in 38. 

As CKD presentation is often asymptomatic, recommended screening studies include serum creatinine measurement, urinalysis, and/or imaging studies of the kidneys. Diabetes, hypertension, genitourinary abnormalities, and autoimmune diseases represent some of the more common conditions associated with kidney disease. People who are older or those who have a family history of kidney disease should also be screened. If the serum creatinine is elevated, or more appropriately the GFR decreases, or if there are abnormalities in the urinalysis or imaging studies, an evaluation for CKD should be performed. ... 

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