Creatinine, analysis

Since collection of all urine from volunteers over a 24-h period may not be possible, creatinine analysis of the composite total urine sample is recommended. This will allow for a more scientific analysis and interpretation of the excretion pattern presented by the worker during the course of the monitoring. 

Calculation of ID using biological monitoring techniques requires the knowledge of the pharmacokinetics of the parent pesticide in laboratory animals. This will allow the use of the parent or its urine metabolite(s) to calculate the total amount of the parent that had been absorbed through the skin of the test subject. The amount of the residue in the urine should be corrected for any molecular weight differences between the parent and its urine metabolite(s) and also corrected for daily urine excretion volumes based on creatinine analysis of the urine samples. 

Lafolie P, Beck O, Blennow G, Boreus L, Borg S, Elwin CE, et al. Importance of creatinine analysis of urine when screening for abused drugs. Clin Chem 1991 37 1927-31. 

Traditionally, creatine has been determined by the Folin method whereby creatine is determined as creatinine by the Jaffe reaction after conversion in boiling acid for an hour, or autoclaving for 20 min at 120°C. Thus, one aliquot of a sample is analyzed for creatinine, and a second part is heated in acid prior to creatinine analysis. The difference between the two answers gives the concentration of creatine. Large errors are often reported. Also note that heating creatine for an hour in 6 mol 1 HCl is reported to liberate sarcosine. 

To satisfy the third of the above criteria, laboratories analyzing for CDU or B2MU also should submit a QA/QC plan for creatinine analysis (CRTU) the QA/QC plan and characterization analyses for CRTU must come from the laboratory performing the CRTU analysis, even if the CRTU analysis is being performed by a contract laboratory. 

The performance requirement for CDU analysis is defined as an analytical result within 1 pg/l urine or 15% of the consensus mean (whichever is greater). For samples exhibiting a consensus mean less than 1 pg/l urine, the performance requirement is defined as a concentration between the detection limit of the analysis and a maximum of 2 pg/l urine. Laboratories also should demonstrate proficiency in creatinine analysis as defined by the CAP. Note that reporting CDU results, other than for the CTQ proficiency samples should be accompanied with results of analyses for CRTU, and these 2 sets of results should be combined to provide a measure of CDU in units of pg/g CRTU. 

The above evaluation supports the following recommendations for a CDU proficiency program. These recommendations address only sampling and analysis procedures for CDU determinations specifically, which are to be reported as an unadjusted pg Cd/I urine. Normalizing this result to creatinine requires a second analysis for CRTU so that the ratio of the 2 measurements can be obtained. Creatinine analysis is addressed in Section 5.4. Formal procedures for combining the 2 measurements to derive a value and a confidence limit for CDU in pg/g CRTU are provided in Section 3.3.3. 

The determination of creatinine in urine by HPLC is a good alternative to the Jaffe method for industrial hygiene laboratories. Sample clarification with SEP-PAKs did not change the amount of creatinine found in urine samples. However, it does protect the analytical column. The results of this creatinine in urine procedure are unaffected by the pH of the urine sample under the conditions tested by this procedure. Therefore, no special measures are required for creatinine analysis whether the urine sample has been stabilized with 10% nitric acid for the Cd analysis or brought to a pH of 7 with 0.11 NaOH for the B2M analysis. 

For creatinine analysis, four enzymes (creatinine amidohydrolase, creatinine kinase, pyruvate kinase, and lactate dehydrogenase) were co-immobilized in a nylon tube reactor [56]. 

Ginman, R., Colliss, ).S., and Knox, J.M. (1983) The use of an immobilized enzyme nylon tube reactor incorporating a four enzyme system for creatinine analysis. AppL Biochem. Biotechnol., 8, 213-226. doi 10.1007/BF02778259... 

Description of Method. Creatine is an organic acid found in muscle tissue that supplies energy for muscle contractions. One of its metabolic products is creatinine, which is excreted in urine. Because the concentration of creatinine in urine and serum is an important indication of renal function, rapid methods for its analysis are clinically important. In this method the rate of reaction between creatinine and picrate in an alkaline medium is used to determine the concentration of creatinine in urine. Under the conditions of the analysis, the reaction is first-order in picrate, creatinine, and hydroxide. 

Much of the early work with certified reference materials was linked to the derivation of reference methods and there was a period in which primary or definitive (i.e. very accurate but usually very complex) and secondary (or usable) methods were reported e.g. steroid hormones (Siekmann 1979), creatinine (Siekmann 1985), urea (Welch et al. 1984) and nickel (Brown et al. 1981). Although there are some application areas, such as checking the concentrations of preparations listed in a pharmacopoeia, where a prescribed, defined method has to be used, in practice such work is limited. However, this approach to chemical analysis is no longer widely used and will not be further discussed. The emphasis now is placed on using RMs to demonstrate that a method in use meets analytical criteria or targets deemed to be appropriate for the application and to develop figures of merit (Delves 1984). 

Obtain serum drug levels for aminoglycosides and/or vancomycin and perform pharmacokinetic analysis. Adjust the dose, if needed, according to the parameters in Table 13-2. Obtain follow-up trough levels at weekly intervals or sooner if renal function is unstable. Follow serum creatinine levels if renal function is unstable. Hearing tests may be scheduled yearly or per patient preference. 

The urine samples were analyzed using a modified version of a published method.8 The method involved fortification of the urine samples with an internal standard 3,4,5-trichloro-2-pyridinyl, which is a structural isomer of the 3,5,6-TCP metabolite of chlorpyrifos hydrolysis of labile acid conjugates to 3,5,6-TCP solvent extraction derivitization to the f-butyl-dimethylsilyl ester of 3,5,6-TCP and subsequent negative-ion chemical ionization gas chromatography/mass spectrometry (GC/MS) analysis. Creatinine was determined in urine using a modification of a method of Fabiny and Erting-shausen.9... 

Analysis of the urinary data. The amount of creatinine and 3,5,6-TCP in each urine collection was calculated from the volume of the urine specimen and the concentration of each in that urine specimen. The amount of creatinine excreted per day was compared across days for each volunteer and to standard literature values for creatinine excretion (i.e., mean 1.8 g/24 hr 95% range, 1.1 to 2.5 g/24 hr). The urine collection was considered to be complete if the amount of creatinine was consistent with the amount of creatinine in the other urine specimens provided by that individual and within the literature range for normal creatinine excretion. 

The second estimate of dose was arrived at through analysis of the collected urine of volunteers for 3,5,6-TCP and creatinine. The second approach is generally considered to yield a more accurate estimate of dose as it measures, indirectly, the amount of test substance absorbed from all routes of exposure. The following estimation of dose is for the liquid turf evaluation only a summarization of data will be given for the granular turf evaluation. 

A study of 398 male and 133 female civil servants in London, England, measured blood pressure, PbB, and serum creatinine concentration the study found no correlation between blood pressure and PbB after adjustment for significant covariates, including sex, age, cigarette smoking, alcohol intake, and body mass index in a stepwise multiple regression analysis (Staessen et al. 1990). 

A report entitled Chemical Trespass was issued in May 2004 by the Pesticide Action Network (Schafer et al., 2006). It contained detailed analysis of 2000/01 National Health and Nutrition Examination Survey (NHANES) OP urinary metabolite data and used published methods to estimate exposure levels to parent compounds from creatinine corrected urinary metabolite levels. They focused on chlorpyrifos and its metabolite 3,4,6-trichloro-2-pyridinol (TCP), and found that chlorpyrifos exposures for children ages 6-11 and 12-19 exceeded EPA s chronic population-adjusted dose (cPAD) by surprisingly wide margins. Geometric mean TCP levels were 3 to 4.6 times higher than the EPA-estimated safe dose, as shown in Fig. 14.2. The more heavily exposed children received daily doses more than ten times the safe level. 

A complete physical examination and laboratory analysis are needed to rule out secondary causes and to assess kyphosis and back pain. Laboratory testing may include complete blood count, liver function tests, creatinine, urea nitrogen, calcium, phosphorus, alkaline phosphatase, albumin, thyroid-stimulating hormone, free testosterone, 25-hydroxyvitamin D, and 24-hour urine concentrations of calcium and phosphorus. Urine or serum biomarkers (e.g., cross-linked N-telopeptides of type 1 collagen, osteocalcin) are sometimes used. 

The biological exposure index (BEI) for occupational exposure to 5 ppm phenol is 250 mg total phenol in urine/g creatinine (ACGIH 1998). The urine should be collected at the end of the 8-hour work shift. The sample can be stored in the refrigerator for 4 days or frozen for at least 3 months before analysis. 

Dash, A.K. and Sawhney, A., A simple LC method with UV detection for the analysis of creatine and creatinine and its apphcation to several creatine formulations, J. Pharm. Biomed. Anal., 29, 939, 2002. 

A volume equivalent to 0.25 mg of creatinine from 500 mL of urine of a healthy adult donor is analyzed as described above. The collection is then spiked with up to ten organic acids (1 mg/ml stock solutions), selected from those with an active calibration curve by GC-MS TIC, to mimic a concentration of 100 pg acid/mg creatinine. The spiked collection is aliquoted into screw-cap vials during continued mixing, then stored frozen. For GC-MS SIM analysis, all compounds listed in Table 3.1.5 are included in the abnormal control, at a concentration matching the fourth point of the calibration curve (1 1 molar ratio to the labeled internal standard, see Table 3.1.5). 

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