Alkaline Picrate Research Articles

Cyanide Content of Commercial Gari from Different Areas of Ekiti State, Nigeria

Gari, a creamy-white granular flour made from fresh cassava tubers have been known to contain residual cyanide (hydrocyanic acid) after processing. Cyanide is poisonous and ingestion of Gari beyond the permissible limit can lead to chronic toxicity. This study therefore investigated the presence of this chemical in Gari samples taken from different areas of Ekiti State in Nigeria to ascertain whether or not they are below the permissible level. Random samples of commercial Gari processed locally were collected from 6 areas of Ekiti State in South West Nigeria and screened for residual cyanide content. The alkaline picrate method was used for the screening. Four of the samples contained cyanide in the range of 2.10-9.10 mgHCN/kg which falls below the permissible limit while the remaining two samples had higher residual cyanide of 11.78 and 15.30mgHCN/kg which is above the permissible limit. WHO permissible limit of cyanide concentration is 10.0mgHCN/kg. The samples with concentration above 10mgHCN/kg are from areas where the cassava mash was fermented for less than 12 hours.

Effect of a Cooked Meat Meal on Serum Creatinine and Estimated Glomerular Filtration Rate in Diabetes-Related Kidney Disease

Fasting is not routinely recommended for renal function tests, despite the known effects of cooked meat on creatinine. We therefore studied variation in creatinine and estimated glomerular filtration rate (eGFR) after a standardized cooked meat meal in 80 subjects: healthy volunteers and diabetic patients with chronic kidney disease (CKD) stages 1 and 2, 3a, 3b, and 4 (n = 16/group). The interventions were a standardized cooked meat and a nonmeat meal, each providing ∼54 g protein, together with 250 mL water, on separate days. Fasting and postprandial blood samples at 1, 2, and 4 h were drawn for creatinine measurement using a kinetic alkaline picrate assay on an Olympus AU640 analyzer. The modified four-variable Modification of Diet in Renal Disease equation traceable to isotope dilution mass spectrometry creatinine was used to calculate eGFR. Consumption of a standardized cooked meat meal significantly increased serum creatinine and resulted in significant fall in eGFR in all stages of CKD studied; 6 of 16 CKD 3a patients were misclassified as CKD 3b. This effect of cooked meat on serum creatinine disappears after 12 h of fasting in all study participants. Creatine in meat is converted to creatinine on cooking, which is absorbed, causing significant increases in serum creatinine. This could impact management, as threshold for commencing and withdrawing certain medications and expensive investigations is defined by eGFR. eGFR calculated using fasting serum creatinine would be a better reflection of kidney function in these patients.

Evaluation of the impact of standardization process on the quality of serum creatinine determination in Italian laboratories

BackgroundCreatinine determination in serum is a key indicator of kidney glomerular function. A reference measurement system for its standardization is available and virtually all IVD manufacturers have aligned their assays to this system. In this study, we verified the impact of these standardization efforts on the results of an Italian EQAS involving about 430 laboratories. MethodWe considered data obtained during 2006, 2010 and 2011 schemes of EQAS Prolarit for control materials with target values assigned by a traceable method (enzymatic assay calibrated against the NIST SRM 967). ResultsThe results showed a good alignment at concentrations ~170μmol/L, with 2011 results — except for one method group — well inside the desirable bias (±4%). At higher concentrations, whereas the bias was small in 2010, for some groups using alkaline-picrate (AP) methods it became significantly negative in 2011. The performance seems to worsen when measuring physiologic concentrations, where a significant positive bias (up to ~20%) is shown by most of the AP-based analytical systems. With few exceptions, no evident improvement in individual assay bias was noted from pre- (2006) to post-standardization (2011) periods. The enzymatic method groups were the only always presenting an acceptable bias at all creatinine concentrations, also showing the lowest between-laboratory variability. ConclusionOur data seem to indicate that the standardization efforts are still having effects lower than expected. Even taking into consideration that some of the bias may derive from non commutability problems, most of the current “standardized” AP-based methods, at the lower creatinine concentrations, seem to present accuracy problems. This inaccuracy can adversely impact the estimation of GFR by equations and the evaluation of kidney function in pediatrics.

Anti-malarial property of steroidal alkaloid conessine isolated from the bark of Holarrhena antidysenterica

BackgroundIn the face of chronic and emerging resistance of parasites to currently available drugs and constant need for new anti-malarials, natural plant products have been the bastion of anti-malarials for thousands of years. Moreover natural plant products and their derivatives have traditionally been a common source of drugs, and represent more than 30% of the current pharmaceutical market. The present study shows evaluation of anti-malarial effects of compound conessine isolated from plant Holarrhena antidysenterica frequently used against malaria in the Garhwal region of north-west Himalaya.MethodsIn vitro anti-plasmodial activity of compound was assessed using schizont maturation and parasite lactate dehydrogenase (pLDH) assay. Cytotoxic activities of the examined compound were determined on L-6 cells of rat skeletal muscle myoblast. The four-day test for anti-malarial activity against a chloroquine-sensitive Plasmodium berghei NK65 strain in BALB/c mice was used for monitoring in vivo activity of compound. In liver and kidney function test, the activity of alkaline phosphatase (ALP) was examined by p-NPP method, bilirubin by Jendrassik and Grof method. The urea percentage was determined by modified Berthelot method and creatinine by alkaline picrate method in serum of mice using ENZOPAK/CHEMPAK reagent kits.ResultsCompound conessine showed in vitro anti-plasmodial activity with its IC50 value 1.9 μg/ml and 1.3 μg/ml using schizont maturation and pLDH assay respectively. The compound showed cytotoxity IC50= 14 μg/ml against L6 cells of rat skeletal muscle myoblast. The isolated compound from plant H. antidysenterica significantly reduced parasitaemia (at 10 mg/kg exhibited 88.95% parasite inhibition) in P. berghei-infected mice. Due to slightly toxic nature (cytotoxicity = 14), biochemical analysis (liver and kidney function test) of the serum from mice after administration of conessine were also observed.ConclusionThe present investigation demonstrates that the compound conessine exhibited substantial anti-malarial property. The isolated compound could be chemically modified to obtain a more potent chemical entity with improved characteristics against malaria.

EVALUATION OF DIURETIC ACTIVITY OF MILK EXTRACT OF SEMECARPUS ANACARDIUM NUT

Semi carpus anacardium ‘Marketing Nut’ is a tropical flowering plant widely distributed in India. Semicarpus anacardium are widely used for its therapeutic potential as immunomodulatory and in folklore the plant material is reported in the treatment of diureti c. Since, the diuretic activity of these plant materials has not been investigated in scientifically controlled studies; the aim of the present study was to evaluate the diuretic potenti al of milk extracts of Semicarpus anacardium seed in normal rats after acute and sub - chronic oral administration. Milk extracts of Semicarpus anacardium seed (150 and 300 mg/kg) along with the reference drug, furosemide (10 mg/kg) were administrated orally to male Wistar rats for 8 subsequent days and their urine output was quantitated at several intervals of time after the dose. Several other parameters such as urinary electrolyte concentration, plasma electrolyte conc entration and creatinine clearance were also measured by flame spectrophotometry and Jaffe alkaline picrate method. After administration of single dose of the milk extracts of Semicarpus anacardium seed, urine output significantly showed equivalent increment at all time points, and at 24 h after the dose, the total volume of urine excreted was highest in furosem ide followed by plant extracts and control group. Both extracts increased the urinary levels of Na + and K + , to about the same extent, while furosemide increased urinary levels of only Na + and decreased urinary K + . Despite changes in urinary excretion of t he electrolytes, plasma Na + and K + levels were not affected by any of the substances. The present study supports the ethnomedical use of Semicarpus anacardium seed for their diuretic effect

Creatinine Estimation and Interference

Sir, Creatinine is one of the most common analyte used as the indicator of glomerular filtration rate (GFR) and kidney function. In 1886, Jaffe reported a reaction of creatinine and picric acid in an alkaline medium forming complex having absorbance maxima at 520 nm. The reaction has been brought to use for the measurement of creatinine by Folin and Wu in 1919. Since then, Jaffe’s reaction has been used for estimation of creatinine in serum and urine sample. For more than 90 years, this method is in use for the measurement of creatinine concentration due to its simplicity and low cost. Creatinine is produced as the byproduct of creatine metabolism and is transported through bloodstream to the kidneys for excretion. Malfunctioning of kidney is reflected by lowering of the amount of creatinine in urine and rise of its level in blood. Creatinine levels in blood and urine also indicate the creatinine clearance, accounting for GFR. Creatinine readings indicate the total kidney GFR which is the sum of filtration rates of all functional nephrons. Early structural damage to the renal cells involving reduction in functional nephron number may not affect an individual’s total GFR as remaining renal units may perform compensatory function, enabling the kidneys to maintain kidney function temporarily even after the loss of functional tissue. Thus, creatinine/GFR may not indicate the early damage to kidney tissue. Jaffe also elaborated the interference in alkaline picrate reaction by number of organic compounds (e.g. acetone, glucose) which has been described as pseudochromogens. Still, creatinine remains the gold standard for measuring the glomerular filtration rate and kidney functioning. And Jaffe method remains the default method for estimation of creatinine. In last century, many caveats in this method were reported which we have indicated in brief in this article. Recently we have reported an interference by streptomycin (an aminoglycoside) in high doses which act as false positive in Jaffe reaction [1]. It is known from literature that aminoglycosides can be nephrotoxic and may potentially affect kidney function. If it is so, then, nephrotoxicity due to high dose of aminoglycosides (say streptomycin) can never be correctly estimated as defect in excreting out creatinine would be masked by the false positive Jaffe reaction given by streptomycin. Antibiotics like cephapirin, cefazolin, cefamandole, cephalothin, and cefoxitin have been shown to interfere with creatinine determination at various concentrations [1, 2]. Phenacemide and cephalothin may interfere either positively or negatively with the determination of creatinine by the Jaffe reaction [3] . Cephalosporin antibiotics have been shown to form non-creatinine chromogen with alkaline picrate reagent and produce false positive results for creatinine. Serum creatinine and creatinine clearance values are positively interfered by cefoxitin in the Jaffe reaction, the routine laboratory method of creatinine measurement. Both invitro and invivo analysis suggest the same [4]. Many biomolecules like bilirubin, glucose, acetone etc. are also known to interfere with the Jaffe method of creatinine estimation and therefore the method has gone through modifications [5]. To overcome the effect of interference specific enzymatic method of creatinine estimation has been also developed [6]. But in-spite of various modification of the Jaffe method and development of the specific enzymatic method for creatinine estimation, the classical alkaline picrate method remains popular in India.

Evaluation of Cyanogen Contents of Cassava and Cassava Based Food Products in Karu, Nasarawa State, North Central Nigeria

Cyanogen contents of seven most consumed cassava based food products in Nasarawa state were evaluated using the alkaline picrate method. These products were subjected to different processing methods such as peeling, washing, grating, fermentation, drying/dewatering, milling/pulvering and frying. The analyses showed reduction in cyanogens contents ranging from 56.33% to 89.58% compare to raw cassava tubers from which they were all produced. These results also showed that cassava processing methods in which fermentation is involved in the multistep processing stages greatly reduced cyanogen contents of the cassava. However, these processing methods did not remove all the cyanogen from the cassava products but reduced it below 10 ppm, recommended by the World Health Organization as safe limit, suggesting that the cassava underwent proper processing to produce safe products. Consumption of these products will not lead to the lethal dose of 35 mg hydrocyanic acid per kg body weight reported by some authors, hence marketing and consumption of these products should be promoted and efforts made to improve the processing methods to further reduce the cyanogen contents of the products. Keyword: Cassava, cyanogens, fermentation, hydrocyanic acid, picric acid,

Streptomycin interference in Jaffe reaction — Possible false positive creatinine estimation in excessive dose exposure

ObjectivesTo study the potential of commonly used aminoglycoside antibiotics to form non-creatinine chromogen with alkaline picrate reagent. Design and methodsWe studied the non-creatinine chromogen formation of various concentrations of streptomycin, amikacin, kanamycin, netilmicin, gentamicin and tobramycin added to known creatinine concentrations by the Jaffe reaction based creatinine estimation. ResultsOnly streptomycin above therapeutic concentrations of 10mg/mL interfered in the Jaffe reaction and acted as non-creatinine chromogen. ConclusionsTherapeutic doses of the aminoglycosides do not form non-creatinine chromogens.

Compensating for the influence of total serum protein in the Schwartz formula

The Schwartz 2009 creatinine-based revised formula is the only pediatric GFR estimating formula, which is compatible with the recent global creatinine standardization. This formula is only applicable if enzymatic creatinine methods are used. We propose an equation, taking into account the relative bias caused by serum proteins to use Jaffe based creatinine data for GFR estimation. In a cohort study of 100 pediatric patients, serum creatinine was measured using a kinetic rate-blanked Jaffe assay (modified kinetic alkaline picrate method), a kinetic rate-blanked Jaffe compensated assay for reactive proteins and an enzymatic assay (creatinine plus method). Serum total protein, albumin, urea, uric acid and total bilirubin were measured with the use of commercial agents. The difference in serum creatinine between the enzymatic method and the compensated Jaffe method was mainly dependent on the total protein concentration in serum (r(2)=0.61, p<0.001). After applying the proposed protein correction, corrected compensated Jaffe results and creatinine clearance values became interchangeable with enzymatic serum creatinine results (r(2)=0.99, p<0.001; Deming regression: slope: 0.9787, intercept: -0.351) and with the newly proposed Schwartz formula, respectively (r(2)=0.99, p<0.001; Deming regression: slope 1.004, intercept: 2.16). In this study, we demonstrated the usability of the alkaline picrate method in the Schwartz formula, taking into account the relative bias caused by serum proteins.

Relação proteína/creatinina na urina versus proteinúria de 24 horas na avaliação de nefrite lúpica

The urinary protein/creatinine ratio has been used instead of 24-hour proteinuria in Nephrology practice for the follow-up of glomerular diseases, considering the advantages of collection and the low cost. However, there are still doubts as to its applicability both for an isolated evaluation and for the follow-up of patients with lupus nephritis. To evaluate 24-hour proteinuria determinations and random urine samples, performing urinary creatinine correction and urinary protein/creatinine ratio in subjects with lupus nephritis. 24-hour proteinuria and urinary protein/creatinine ratio were determined by conventional methods (automated Pyrogallol for proteinuria and alkaline picrate for creatinine). Seventy-eight urine samples of 41 patients diagnosed with systemic lupus erythematosus, according to the American Rheumatology Association, with lupus nephritis, were analyzed, and a good correlation between 24-hour proteinuria and urinary protein/creatinine ratio (r = 0.9010 and r² = 0.813) was observed. However, a poor correlation between random proteinuria (without creatinine correction) versus 24-hour proteinuria (r = 0.635 and r² = 0.403) or versus urinary protein/creatinine ratio (r = 0.754 and r² = 0.569) was seen. 24-hour proteinuria and urinary protein/creatinine ratio were useful in the follow-up of each case. However, we observed that the absolute values were different, which did not allow the replacement of one for the other during follow-up, especially when this result is used to define the activity of the disease. Based on these results, we suggest a period of intersection from one to the other (two to three determinations by both methods), and the choice of one marker for proteinuria follow-up, if necessary.

Mouse model of proximal tubule endocytic dysfunction

Several studies have indicated the central role of the megalin/cubilin multiligand endocytic receptor complex in protein reabsorption in the kidney proximal tubule. However, the poor viability of the existing megalin-deficient mice precludes further studies and comparison of homogeneous groups of mice. Megalin- and/or cubilin-deficient mice were generated using a conditional Cre-loxP system, where the Cre gene is driven by the Wnt4 promoter. Kidney tissues from the mice were analysed for megalin and cubilin expression by quantitative reverse transcription-polymerase chain reaction, western blotting and immunohistochemistry. Renal albumin uptake was visualized by immunohistochemistry. Twenty-four-hour urine samples were collected in metabolic cages and analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and western blotting. Urinary albumin/creatinine ratios were measured by ELISA and the alkaline picrate method. The Meg(lox/lox);Cre(+), Cubn(lox/lox);Cre(+) and Meg(lox/lox), Cubn(lox/lox);Cre(+) mice were all viable, fertile and developed normal kidneys. Megalin and/or cubilin expression, assessed by immunohistology and western blotting, was reduced by >89%. Consistent with this observation, the mice excreted megalin and cubilin ligands such as transferrin and albumin in addition to low-molecular weight proteins. We further show that megalin/cubilin double-deficient mice excrete albumin with an average of 1.45 ± 0.54 mg/day, suggesting a very low albumin concentration in the glomerular ultrafiltrate. We report here the efficient genetic ablation of megalin, cubilin or both, using a Cre transgene driven by the Wnt4 promoter. The viable megalin/cubilin double-deficient mice now allow for detailed large-scale group analysis, and we anticipate that the mice will be of great value as an animal model for proximal tubulopathies with disrupted endocytosis.

Focusing on the clinical impact of standardization of creatinine measurements: a report by the EFCC Working Group on Creatinine Standardization

The recent campaign for standardization of creatinine measurements has been promoted to allow the widespread use of formulas for estimating the glomerular filtration rate (GFR). However, studies on trueness verification and measurement interferences still show disappointing interassay variation of serum creatinine results. Creatinine recalibration has major clinical consequences. In particular, in pediatrics where reference ranges for serum and plasma creatinine are low, calculation of the GFR is problematic when based on alkaline picrate methods because of method non-specificity and the lack of appropriate GFR estimating formulas. Therefore, enzymatic creatinine assays are preferred. In the near future, cystatin C might offer an interesting alternative for GFR estimation. For the calculation of drug doses, the Modification of Diet in Renal Disease study formula generally offers reliable data. However, attention has to be paid to the elderly. Also, the calculation of the Model for End-Stage Liver Disease score, which is used to prioritize patients for liver transplantation, may significantly be influenced by recalibration of creatinine assays. Creatinine restandardization may also affect the current guidelines for referral of chronic kidney disease patients to nephrologists.

Simple picrate method for the determination of cyanide in cassava flour

A simple picrate method was used to quantify the cyanide contents of food samples. The cyanide in the food samples reacted with hot 20% HCl solution to produce hydrogen cyanide vapour which reacted with alkaline picrate test strips to form red colour on the test strips. The red coloured complex on the strips was extracted with 50% ethanol solution and the absorbance of the extract was measured at 510nm using a spectrophotometer. The method was reproducible and cyanide as low as 1 microgram could be determined. Cyanide levels of all the cassava varieties tested were higher than the 10ppm WHO safe level. Recovery of cyanide from acyanogenic foods fortified at levels of 5 and 10mg KCN/10g were 98.6% and 99.1% respectively. The picrate method is simple and useful for routine determination of cyanide content of cassava flour.Keywords: Picrate method, Cyanide, Cassava flour

Synthesis and Investigation of Host-[2]Rotaxanes That Bind Metal Cations

Materials that bind metal cations are highly sought after for new devices. In this report, we show that rotaxanes can transfer metal cations with picrate, perchlorate, or chloride counterions from an aqueous solution into chloroform. The rotaxanes contain a dibenzyl-24-crown-8 ether as the wheel with either a benzyl-18-crown-6 ether (CEBG-R1-3) or a 3,5-dimethylbenzyl moiety (ArBG-R) as one blocking group. Alkali and alkaline picrate salts were efficiently extracted from an aqueous solution, presented in the millimolar range, into chloroform. Large association constants were derived for the complexes in chloroform, especially for the divalent cation Mg(2+). Switching the counterion to chloride greatly diminished the amount of salt extracted. To explore the transfer mechanism of the rotaxanes, a comparison was made in the amount of NaClO(4), KClO(4), NaCl, and KCl extracted by CEBG-R1, ArBG-R, benzyl-18-crown-6 ether (B18C6), and two model compounds, which were used to represent the crown-ether blocking group and the axle of a rotaxane. Two-dimensional NMR analysis was performed on the rotaxane-cation complexes in CDCl(3). We found that the host rotaxanes transfer the perchlorate salts poorly when compared to B18C6, but they transfer chloride salts from 1 M salt solutions, whereas B18C6 does not. The transfer of chloride salts appears to rely on an allosteric type relationship between the binding of the chloride ion and metal cation to a rotaxane. Accordingly, when chloride binds to the dialkylammonium ion of the axle, the wheel moves along the axle and forms a binding site for a metal cation. In this report we demonstrate that host rotaxanes can bind metal cations, change their geometries upon cation and anion association, and operate through allosteric mechanisms, making them promising candidates for molecular devices.

Determination of Cyanide in Amanitia muscaria Samples Using Alkaline Picrate Method

Analytical methods were developed for the detection of cyanide in Amanitia muscaria samples using the alkaline picrate method. Dried mushroom samples contained in glass bottles were treated with acid solution and maintained at 80 C for 10 min. Hydrogen cyanide vapours librated from the samples o reacted with alkaline picrate solution on Whatman filter paper strips to form red-coloured complex on the test strips. The red coloured compound on the test strips were extracted with 50% ethanol solution and the extract absorbance read at 510 nm. A linear relationship was obtained between the ranges of 0-200 µg CN. Cyanide was detected in mushroom samples at the levels of 84-712 µg/10 g sample. Recovery of cyanide from the samples demonstrated that cyanide poisoning could occur in populations due to prolonged intake of toxigenic mushroom samples. Association between cyanide intake from cyanogenic mushroom and the manifestation of severe human diseases were discussed.

Ethnic coefficients for glomerular filtration rate estimation by the Modification of Diet in Renal Disease study equations in the Korean population.

Race and ethnicity are influential in estimating glomerular filtration rate (GFR). We aimed to find the Korean coefficients for the Modification of Diet in Renal Disease (MDRD) study equations and to obtain novel proper estimation equations. Reference GFR was measured by systemic inulin clearance. Serum creatinine (SCr) values were measured by the alkaline picrate Jaffé kinetic method, then, recalibrated to CX3 analyzer and to isotope dilution mass spectrometry (IDMS). The Korean coefficients for the 4 and 6 variable MDRD and IDMS MDRD study equations based on the SCr recalibrated to CX3 and to IDMS were 0.73989/0.74254 and 0.99096/0.9554, respectively. Coefficients for the 4 and 6 variable MDRD equations based on the SCr measured by Jaffé method were 1.09825 and 1.04334, respectively. The modified equations showed better performances than the original equations. The novel 4 variable equations for Korean based on the SCr measured and recalibrated to IDMS were 107.904×SCr-1.009×age-0.02 (×0.667, if woman) and 87.832×SCr-0.882×age0.01 (×0.653, if woman), respectively. Modified estimations of the MDRD and IDMS MDRD study equations with ethnic coefficients and the novel equations improve the performance of GFR estimation for the overall renal function.

Modification of Jaffe’s kinetic method decreases bilirubin interference: A preliminary report

The negative interference of bilirubin on serum creatinine determined by the kinetic alkaline picrate (Jaffe) reaction is the unresolved problem. Though high performance liquid chromatography and gas chromatography with mass spectroscopy have been proposed to be gold standards for creatinine estimation but they are not readily available in most of the clinical chemistry laboratories due to economic and technical constraints. Most of the present day analyzers use Jaffe's kinetic method without deproteinization. Though enzymatic methods are now routinely used as most accurate method but they are not acceptable due to cost constraints. Hence this study was planned to find out a possible solution to the problem of bilirubin interference by a minor modification in the commonly used Jaffe method so that it is amenable for use on the currently used analyzers.

Portable microfluidic system for determination of urinary creatinine

A simple, low cost and portable microfluidic system based on a two-point alkaline picrate kinetic reaction has been developed for the determination of urinary creatinine. The creatinine reacts with picric acid under alkaline conditions, forming an orange-red colour, which is monitored on PDMS microchip using a portable miniature fibre optic spectrometer at 510 nm. A linear range was displayed from 0 to 40 mg L −1 creatinine ( r 2 = 0.997) with a detection limit of 3.3 mg L −1 (S/N = 3). On-chip absorbance signals are reproducible, with relative standard deviations (RSDs) of 7.1%, when evaluated with 20 mg L −1 creatinine ( n = 10). The standard curves in which the intra-run CVs (4.7–6.8%) and inter-run CVs (7.9%) obtained were performed on three different days and exhibited good reproducibility. The method was highly correlated with the conventional spectrophotometric method when real urine samples were evaluated ( r 2 = 0.948 ; n = 15).

Evaluation of matrix effects of reference materials in serum creatinine measurements

Objective To evaluate the trueness of routine systems for serum creatinine measurement and the matrix effects of creafinine reference materials on the systems. Methods The Clinical and Laboratory Standards Institute (CLSI) EP14-A2 protocol was used for the study and an isotope dilution liquid chromatography tandem mass spectrometry (ID-LC/MS/MS) method was used as the comparative method. Fory fresh patient specimens, 15 EQA materials, 13 calibrators, two control materials and 8 frozen serum materials were measured by the comparative method and 15 routine systems (7 enzymatic methods and 8 alkaline picrate methods). Matrix effects were assessed by using the EP14-A2 procedure, and the trueness of the evaluated methods were assessed by comparing the results of the 40 fresh patient specimens obtained with the evaluated methods and the comparative method. Results Tweenty-nine of 30 commercial materials showed matrix effects on the alkaline picrate systems, and 13 of the commercial materials showed matrix effects on the enzymatic systems. Fresh frozen serum materials prepared at the National Center for Clinical Laboratories showed no matrix effect on all 15 routine systems. Calibration biases were observed on 8 alkaline picrate systems and some enzymatic methods. Conclusions Matrix effect, calibration bias and nonspecificity in serum creatinine measurements. Continued efforts are needed for improving the trueness and comparability of serum creatinine measurements. Key words: Creatinine; Isotope labeling; Chromatography. liquid; Tandem mass spectrometry; Picrates; Clinical enzyme tests

Prime Time for Enzymatic Creatinine Methods in Pediatrics

The literature regarding the nonspecificity of applications of the Jaffe (alkaline picrate) reaction for creatinine is generally outdated. We conducted a specificity study to update the nonspecificity information for current Jaffe and enzymatic creatinine assays. Two serum pools with creatinine concentrations within the pediatric reference interval were spiked with albumin, IgG, unconjugated bilirubin, adult hemoglobin (Hb A), and fetal hemoglobin (Hb F) to produce 1 unspiked and 5 spiked samples per pool. The 35 laboratories participating in the survey used a total of 14 method-analyzer combinations. Measurements were performed in triplicate in a single run in accordance with manufacturer instructions. Absolute differences in creatinine concentration between spiked and unspiked samples were calculated per laboratory. Mixed ANOVA was used to quantify the interferent-related CV component for the Jaffe and enzymatic methods. The interference by bilirubin and Hb A on serum creatinine measurements was <10% for most of the Jaffe and enzymatic methods. Obvious interference was observed among the Jaffe methods in samples spiked with Hb F, albumin, and IgG, but not among the enzymatic methods. The within-laboratory interferent-related CVs for the Jaffe method-analyzer combinations ranged from 8.0%-27% at a creatinine concentration of 40.4 micromol/L (0.46 mg/dL) and from 5.4%-15% at 73.4 micromol/L (0.83 mg/dL). Enzymatic methods had within-laboratory interferent-related CVs of <4% at both concentrations. Albumin, IgG, and Hb F interfered with Jaffe creatinine assays, leading to inaccuracies in estimated glomerular filtration rates that are clinically important, especially in children and neonates. Because protein error and Hb F interference do not occur with any of the enzymatic methods tested, we conclude that enzymatic creatinine methods are preferred for evaluation of kidney function in pediatric cases.