[Predictors of choledocholithiasis in patients sustaining acute biliary pancreatitis]

BACKGROUND

To assess the role of alkaline phosphatase (AP), gamil-glutamyltransferase (gammaGT) and abdominal ultrasound (US) as predictors of choledocholithiasis in patients sustaining acute biliary pancreatitis.

METHODS

Data was prospectively collected during a period of 31 months. Forty patients were included, 30 were female and the mean age was 49 +/- 16. All patients sustaining acute biliary pancreatitis were enrolled. Patients with clinical jaundice and severe pancreatitis were excluded. Serum content of AP and gGT as well as US were assessed at admission and 48 hours before cholecistectomy. All patients underwent intra-operative cholangiography (IOC) or pre-operative endoscopic retrograde cholangiography (ERCP), which was indicated based on the odds of choledocholithiasis. In order to identify the predictors of choledocholithiasis, variables were compared between patients sustaining or not such alteration in cholangiography. Student t, Fisher and chi square tests were used for statistical analysis, considering p<0.05 as significant. Positive (PPV) and negative predictor values (NPV) were calculated for each variable.

RESULTS

Upon admission, 15 (37%) patients sustained biliary tract dilatation and 5 (12%) choledocholithiasis at the US. Forty eight hours before the operation, 34 (85%) patients had altered levels of gGT and 16 (40%) of AP. Pre-operative US showed biliary tract dilatation in nine patients and choledocholithiasis in three. ERCP was performed in 15 (37%) cases. Higher PPV (55%) was attributed to pre-operative US, which had also a NPV of 96%.

CONCLUSION

The best predictor of choledocholithiasis in patients sustaining mild acute pancreatitis was the biliary tract dilatation in pre-operative US.

Reference intervals for eight enzymes in blood of adult females and males measured in accordance with the International Federation of Clinical Chemistry reference system at 37 degrees C: part of the Nordic Reference Interval Project

As part of the Nordic Reference Interval Project we present reference intervals for alanine transaminase (ALT), aspartate transaminase (AST), creatine kinase (CK), lactate dehydrogenase (LD), alkaline phosphatase (ALP), gamma-glutamyltransferase (GT), amylase (AMY) and pancreatic type of AMY in blood of adult males and females. A total of 3036 reference persons, all of whom considered themselves to be in good health, were recruited by 102 Nordic clinical biochemical laboratories. Exclusions were undertaken on the basis of predefined biochemical and clinical criteria. Enzyme activities in serum and plasma were measured in the different laboratories using various commercially available routine measurement systems at 37 degrees C. Only results obtained with the International Federation of Clinical Chemistry (IFCC) compatible measuring systems were selected for estimation of the enzyme reference intervals. The final number of results on each enzyme varied from 459 (LD) to 2300 (ALT). The 2.5 and 97.5 percentile reference limits were calculated by a non-parametric method in accordance with the IFCC recommendations, using the Refval 4.0 data program. Statistical partitioning testing was undertaken to decide whether the reference intervals ought to be partitioned according to gender and/or age. For most of the enzymes, but not for all, the upper reference limits were found to be higher than those that have been in general use until now.

[Uncertainty of measurement as an integral part of the result and a tool of quality of work improvement for the chemical-toxicology laboratory]

An uncertainty in measurements is a numerical defined range that is supposed to find a true value with a given level of probability. The purpose of this study was to estimate a type A and B of uncertainty in the analysis of ethanol using the ADH method and prove it to be useful in lab practice. A large percentage of uncertainty was shown for pipetting of the ADH and perchloric acid solutions. This result formed the basis to make an effort in order to improve the procedure. The results of uncertainty of measurements given by method B are similar to the empiric method A results. The reduction of expenses and time saving of the analysis is an important advantage of the described way of uncertainty.

Faecal pancreatic elastase--1 a non invasive measure of exocrine pancreatic function

BACKGROUND

Faecal pancreatic elastase-1 is a laboratory based test used for the diagnosis or exclusion of exocrine pancreatic insufficiencies. Pancreatic elastase-1, is released into blood circulation during inflammation of the pancreas, but unlike most pancreatic enzymes it is stable during intestinal passage and not degraded.

OBJECTIVES

The major objective of this work was to establish the assay of faecal pancreatic elastase-1 in spot stool samples as an exocrine pancreatic function test at Korle-Bu (a referral) hospital in Ghana, for the diagnosis of pancreatic diseases.

METHOD

Twenty-five apparently healthy persons; mean age of 43.4 years and thirty-two patients with various pancreatic diseases, mean age 51.4 years were referred for the test based on clinical presentation, imaging studies and biopsy findings. The male to female ratio was 6.4:3.6 and 8.1:1.9 respectively. An ELISA technique which recognizes human pancreatic elastase-1 from spot stool samples was employed for the test and read photometrically at 405nm.

RESULTS

Elastase-1 activity in spot stool samples from apparently healthy group ranged from 165 to 870mg/g with a mean of 379 (SE 41)mg/g, and a range of 20 to 285mg/g with a mean of 112.9 (SE 11.6)mg/g obtained for the pancreatic disease group. Disease severity was classified as mild to moderate with elastase-1 concentration between 100 and 200mg/g stool and the severe pancreatic insufficiency group with elastase-1 concentration of less than 100mg/g stool. The pancreatic elastase-1 was found to be stable in faeces for several weeks when stored frozen, hence the convenience for batch determinations.

CONCLUSION

The test is non invasive and can assist with the diagnosis of inflammatory conditions of the pancreas where imaging results are equivocal.

Inaccuracy of routine creatinine measurement in canine urine

BACKGROUND

Urine creatinine concentration often is used in ratios such as urine protein:creatinine to compensate for dilution or concentration of spot urine samples.

OBJECTIVE

The purpose of this study was to compare the accuracy of different techniques of urine creatinine measurement currently available for veterinary practitioners.

METHODS

In 104 samples of canine urine diluted 1:20 with distilled water, creatinine concentration was measured using a kinetic Jaffé reaction assay, and an enzymatic technique on an automatic analyzer (Elimat) and 3 benchtop analyzers (Reflovet, Scil; Vitros DT2, Ortho-Clinical Diagnostics; Vettest 8008, IDEXX) used in veterinary practice.

RESULTS

The Jaffé and enzymatic techniques on the Elimat were not significantly different, and their inaccuracy tested with human control urines was <5%. The benchtop analyzers underestimated creatinine concentration, especially at concentrations >2000 mg/L. Inaccuracy was higher with multilayer slide technology systems (Vitros and Vettest) than with the Reflovet system. Results were approximately 25% and 2% lower, respectively, than with the Elimat at urine creatinine concentrations about 2000 mg/L.

CONCLUSION

Inaccuracy in urine creatinine measurements using benchtop analyzers should be taken into account when defining decision thresholds, which should be corrected according to the method used to avoid misinterpretations.

Comparison between the enzymatic vitros assay for creatinine determination and three other methods adapted on the Olympus analyzer

To evaluate the relationship between the enzymatic Vitros assay for creatinine determination and other methods, we determined creatinine concentration in 400 heparin samples. Plasma creatinine level was successively determined on the Vitros 750 analyzer (Johnson & Johnson Co., Rochester, NY) and on the Olympus AU2700 analyzer (Olympus France, Rungis, France), using three reagents in the same assay: Olympus-Jaffé and two enzymatic commercial kits-Crea Plus (Roche Diagnostics, Meylan, France) and Enzymatic Creatinine (Randox, Mauguio, France). Comparison of Jaffé and enzymatic measurements of plasma creatinine levels revealed a high correlation when considering all values ranged from 20-1000 micromol/l (r > 0.99). However, for values <60 micromol/l, enzymatic reagents provided best results. Enzymatic methodology is a better clinical choice for the accurate measurement of creatinine, especially for neonates, pediatrics, and hematology units. Because analytical performance and the costs of Randox creatinine were satisfactory for our laboratory, this method, adapted on the Olympus analyzer, was chosen for routine determination of creatinine levels. According to the Valtec protocol (8), no interferences such as hemolysis, lipemia, or bilirubin were detected for Enzymatic Creatinine Randox.

Multicenter evaluation of the commutability of a potential reference material for harmonization of enzyme activities

Standardization of laboratory results allows for the use of common reference intervals and can be achieved via calibration of field methods with secondary reference materials. These harmonization materials should be commutable, i.e., they produce identical numerical results independent of assay principle or platform. This study assessed the commutability of a cryolyoprotectant-containing harmonization material, obtained from the Dutch Foundation for Quality Assessment in Clinical Laboratories, that is intended to harmonize measurements of enzyme activities within the Dutch project “Calibration 2000”. The catalytic concentrations of alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, γ-glutamyltransferase and creatine kinase were analyzed in pooled patient sera and in the reference material in 14 laboratories. On liquid chemistry analyzers the harmonization material behaves like patient material. The enzyme activities measured in it fall on the regression lines calculated from activities measured in serum samples. For dry chemistry analyzers the activities of all enzymes measured in the harmonizator differ from the serum-based regression line. We show that this is due to the sucrose-containing cryolyoprotectant in the harmonization material. For each enzyme, correction factors were calculated that compensated for the bias and proved to be constant between reagent lots. Depending on the enzyme activity measured, application of these factors leads to 2- to 10-fold reduction of between-laboratory percentage coefficient of variation. Thus, additives to (potential) reference materials may alter their matrix in a way that interferes with analysis on certain test systems. The bias caused may be quantifiable and correctable. Establishment of correction factors leads to analytical uncertainties and costs. Therefore, matrix-based materials without additives should be selected as reference materials.

Establishment of reference intervals for enzyme catalytic activity concentration measurements at 37 degrees C--a practical approach

The change from measuring enzyme catalytic activity concentrations from 25 degrees C to 37 degrees C in the German Federal Republic has led to the need for new reference ranges for defined patient groups and for healthy individuals. Up to now, these are only present as tentative values and are incomplete, especially for children. This article describes a method for deriving reference ranges from results obtained from measurement at 25 degrees C and 37 degrees C and the use of percentiles to establish values for 37 degrees C. A total of 1,111,378 data from 507,305 patients were used to establish reference ranges for the following 11 enzymes at 37 degrees C using the test kits from Roche Diagnostics measured on the Modular analyser: acid phosphatase, alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, cholinesterase, creatine kinase, creatine kinase - MB subunit, gamma glutamyl transpeptidase, glutamate dehydrogenase, lactate dehydrogenase and lactate dehydrogenase - isoenzyme 1. The computed reference ranges from the data used gave rise to reference ranges, some of which were in agreement with the data from the producer, some of which, however, showed deviations from the values given by the producer. Ranges for newborns, children and adolescents could be computed with the prerequisite that ranges for 25 degrees C were available and that these had been established and validated. This method of establishing reference ranges for catalytic enzyme activities can be used for all producers, providing the number of data used is sufficient to allow for valid statistical analysis.

Measurement of von Willebrand factor-cleaving protease (ADAMTS-13) activity in plasma: a multicenter comparison of different assay methods

A severely deficient ADAMTS-13 activity (<5%) is a key laboratory finding confirming the diagnosis of thrombotic thrombocytopenic purpura (TTP), whereas a mildly or moderately decreased activity is found in various other conditions. Laboratory tests for ADAMTS-13 activity must reliably identify a severe deficiency and detect inhibitory antibodies against ADAMTS-13. We carried out a multicenter comparison of different assays for ADAMTS-13 activity in plasma, including the quantitative immunoblotting of degraded von Willebrand factor (VWF) substrate, the residual collagen binding activity and ristocetin cofactor activity of degraded VWF, and an immunoradiometric assay. The main goal was to investigate whether all assays concordantly identified severe ADAMTS-13 deficiency and detected inhibitory antibodies. ADAMTS-13 activity was determined by five laboratories in 30 plasma samples of patients with hereditary and acquired TTP and other conditions. ADAMTS-13 activity values of the samples ranged from <3% to > 100%. Concerning the identification of a severe ADAMTS-13 deficiency, good interassay and interlaboratory agreement was observed with only one false-negative and two false-positive results by two laboratories using a collagen binding assay. For samples with normal or mildly to moderately reduced ADAMTS-13 activity, results were less concordant. There was good agreement for the detection of strong inhibitors. We conclude that all assays investigated are useful as a screening test in suspected TTP. Further assay improvement is needed, however.

IFCC primary reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C. International Federation of Clinical Chemistry and Laboratory Medicine. Part 4. Reference procedure for the measurement of catalytic concentration of alanine aminotransferase

This paper is the fourth in a series dealing with reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C and the certification of reference preparations. Other parts deal with: Part 1. The Concept of Reference Procedures for the Measurement of Catalytic Activity Concentrations of Enzymes; Part 2. Reference Procedure for the Measurement of Catalytic Concentration of Creatine Kinase; Part 3. Reference Procedure for the Measurement of Catalytic Concentration of Lactate Dehydrogenase; Part 5. Reference Procedure for the Measurement of Catalytic Concentration of Aspartate Aminotransferase; Part 6. Reference Procedure for the Measurement of Catalytic Concentration of Gamma-Glutamyltransferase; Part 7. Certification of Four Reference Materials for the Determination of Enzymatic Activity of Gamma-Glutamyltransferase, Lactate Dehydrogenase, Alanine Aminotransferase and Creatine Kinase at 37 degrees C. A document describing the determination of preliminary upper reference limits is also in preparation. The procedure described here is deduced from the previously described 30 degrees C IFCC reference method. Differences are tabulated and commented on in Appendix 2.

IFCC primary reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C. International Federation of Clinical Chemistry and Laboratory Medicine. Part 5. Reference procedure for the measurement of catalytic concentration of aspartate aminotransferase

This paper is the fifth in a series dealing with reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C and the certification of reference preparations. Other parts deal with: Part 1. The Concept of Reference Procedures for the Measurement of Catalytic Activity Concentrations of Enzymes; Part 2. Reference Procedure for the Measurement of Catalytic Concentration of Creatine Kinase; Part 3. Reference Procedure for the Measurement of Catalytic Concentration of Lactate Dehydrogenase; Part 4. Reference Procedure for the Measurement of Catalytic Concentration of Alanine Aminotransferase; Part 6. Reference Procedure for the Measurement of Catalytic Concentration of Gamma-Glutamyltransferase; Part 7. Certification of Four Reference Materials for the Determination of Enzymatic Activity of Gamma-Glutamyltransferase, Lactate Dehydrogenase, Alanine Aminotransferase and Creatine Kinase at 37 degrees C. A document describing the determination of preliminary upper reference limits is also in preparation. The procedure described here is deduced from the previously described 30 degrees C IFCC reference method. Differences are tabulated and commented on in Appendix 3.

A rapid direct telomerase assay method using 96-well streptavidin plates

We have developed a high-throughput direct assay methodfor the assay of telomerase activity that improves on previous direct telomerase assays in two ways that allow larger numbers of samples to be conveniently processed: (i) 96-well streptavidin coated plates are used to bind and wash biotinylated primer extension products from the telomerase assay, as opposed to tubes containing streptavidin-coated magnetic beads; and (ii) storage phosphor-imagery is used instead of film autoradiography to detect telomerase products after being washed and released from the streptavidin-derivatized matrix. This method improves on previous direct assay methods using magnetic beads by allowing larger numbers of samples to be conveniently assayed. Also, the total activity of the radiolabeled nucleotides used in this procedure is significantly lower than that used in standard direct telomerase assays, lowering costs and exposure to radioactivity. We have validated the assay by repeating, in triplicate, the IC50 determination of rivanol, our previously identified telomerase inhibitor.

Molecular study of the hydroxymethylbilane synthase gene (HMBS) among Polish patients with acute intermittent porphyria

Acute intermittent porphyria (AIP), an autosomal dominant disorder of heme biosynthesis, is due to mutations in hydroxymethylbilane synthase (HMBS; or porphobilinogen deaminase, PBGD) gene. In this study, we analyzed 20 Polish patients affected by AIP and we were able to characterize seven novel mutations. A nonsense mutation (Y46X), two frameshift mutations (315delT and 552delT) and a 131bp deletion (nucleotides 992-1123) give rise to truncated proteins. A donor splice site mutation IVS12+2T>C predicts skipping of exon 12. A missense mutation (D61Y) was identified in two apparently unrelated patients with a clearly clinical indication of AIP. An inframe 3-bp deletion (278-280delTTG) results in the removal of V93 from the enzyme. In addition to the novel mutations, nine previously described HMBS gene mutations-R26H, G111R, IVS7+1G>A, R149X, R173Q, 730-731delCT, R225X, 982-983delCA and G335D-were identified in this cohort. Our results demonstrate that molecular analysis of the PBGD gene is a more reliable method comparing to enzymatic assay in the diagnosis of AIP. Although more than 170 different mutations are known to the HMBS gene so far, over 40% of all mutations identified among the Polish AIP patients of this study are novel mutations, indicating the heterogeneity of molecular defects causing AIP.

IFCC Primary Reference Procedures for the Measurement of Catalytic Activity Concentrations of Enzymes at 37°C. Part 7. Certification of Four Reference Materials for the Determination of Enzymatic Activity of γ-Glutamyltransferase, Lactate Dehydrogenase, Alanine Aminotransferase and Creatine Kinase according to IFCC Reference Procedures at 37°C

This paper is the seventh in a series dealing with reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C and the certification of reference preparations. Other parts deal with: Part 1. The Concept of Reference Procedures for the Measurement of Catalytic Activity Concentrations of Enzymes; Part 2. Reference Procedure for the Measurement of Catalytic Concentration of Creatine Kinase; Part 3. Reference Procedure for the Measurement of Catalytic Concentration of Lactate Dehydrogenase; Part 4. Reference Procedure for the Measurement of Catalytic Concentration of Alanine Aminotransferase; Part 5. Reference Procedure for the Measurement of Catalytic Concentration of Aspartate Aminotransferase; Part 6. Reference Procedure for the Measurement of Catalytic Concentration of Gamma-Glutamyltransferase. A document describing the determination of preliminary reference values is also in preparation. The certification of the catalytic activity concentrations as determined by the recently elaborated IFCC primary reference methods at 37 degrees C of four enzyme preparations, namely IRMM/IFCC 452 (gamma-glutamyltransferase), IRMM/IFCC 453 (lactate dehydrogenase 1), IRMM/IFCC 454 (alanine aminotransferase) and IRMM/IFCC 455 (creatine kinase) is described. Homogeneity data were derived from previous results. Stability was assessed using recently obtained data as well as data from previous stability studies. The collaborative study for value assignment was performed under a strict quality control scheme to ensure traceability to the primary reference method. Uncertainty of the materials was assessed in compliance with the Guide to the Expression of Uncertainty in Measurement. The certified values obtained at 37 degrees C are 1.90 microkat/l +/- 0.04 microkat/l (114.1 U/l +/- 2.4 U/l), for gamma-glutamyltransferase, 8.37 microkat/l +/- 0.12 microkat/l (502 U/l +/- 7 U/l), for lactate dehydrogenase 1, 3.09 microkat/l +/- 0.07 microkat/l (186 U/l +/- 4 U/l), for alanine aminotransferase and 1.68 microkat/l +/- 0.07 microkat/l (101 U/l +/- 4 U/l), for creatine kinase. The materials are intended for internal quality control as well as for the evaluation of test systems as required by recent European Union legislation. Furthermore, the materials can be used to transfer accuracy from a reference method to a routine procedure provided the procedures exhibit the same analytical specificity and the certified materials are commutable.

IFCC Primary Reference Procedures for the Measurement of Catalytic Activity Concentrations of Enzymes at 37C. Part 6. Reference Procedure for the Measurement of Catalytic Concentration of γ-Glutamyltransferase

This paper is the sixth in a series dealing with reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C and the certification of reference preparations. Other parts deal with: Part 1. The Concept of Reference Procedures for the Measurement of Catalytic Activity Concentrations of Enzymes; Part 2. Reference Procedure for the Measurement of Catalytic Concentration of Creatine Kinase; Part 3. Reference Procedure for the Measurement of Catalytic Concentration of Lactate Dehydrogenase; Part 4. Reference Procedure for the Measurement of Catalytic Concentration of Alanine Aminotransferase; Part 5. Reference Procedure for the Measurement of Catalytic Concentration of Aspartate Aminotransferase; Part 7. Certification of Four Reference Materials for the Determination of Enzymatic Activity of Gamma-Glutamyltransferase, Lactate Dehydrogenase, Alanine Aminotransferase and Creatine Kinase at 37 degrees C A document describing the determination of preliminary upper reference limits is also in preparation. The procedure described here is deduced from the previously described 30 degrees C IFCC reference method. Differences are tabulated and commented on in Appendix 1.

[Improvement of inter-laboratory imprecision in enzyme measurements]

The traceability chains of the enzyme measurement system were established based on technological advances in instrumentation and reagent systems. The values assigned in reference materials (Japan Certified Enzyme Reference Materials; JCERM) were transferred to daily laboratory analysis via enzyme calibrators included in industrial reagent kits. The imprecision between laboratories was then minimized to within 4 percent in six enzymes, AST, ALT, LD, ALP, CK and gamma-GT.

Establishing a reference system in clinical enzymology

The goal of standardization for measurements of catalytic concentrations of enzymes is to achieve comparable results in human samples, independent of the reagent kits, instruments and laboratory where the procedure is carried out. To pursue this objective, the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) has launched a project to establish a reference system in clinical enzymology. This system is based on three hinges: a) extensively evaluated and carefully described reference procedures, b) certified reference materials and c) a network of reference laboratories operating in a highly controlled manner. The original IFCC-recommended procedures for alanine aminotransferase, aspartate aminotransferase, creatine kinase, gamma-glutamyltransferase, lactate dehydrogenase and alpha-amylase have been slightly modified to optimize them at 37 degrees C, with the definition of detailed operating procedures. A group of laboratories perform these procedures manually, with self-made reagents on carefully calibrated instruments. Partially purified and stabilized materials, prepared in the past by the Community Bureau of Reference, have been re-certified by these laboratories for alanine aminotransferase, creatine kinase, gamma-glutamyltransferase and lactate dehydrogenase activities. Using these materials and the manufacturer's standing procedures, industry can assign traceable values to commercial calibrators. Thus, clinical laboratories, which will use routine procedures with these validated calibrators to measure human specimens, can finally obtain values which are traceable to reference procedures.

Drug interference in clinical chemistry: recommendation of drugs and their concentrations to be used in drug interference studies

A group of international experts prepared two lists of drugs with their serum/plasma and urine concentrations, which should be used when evaluating the performance of a new laboratory method. The two lists were verified by running in vitro interference studies in three European laboratories on Hitachi instruments. The study identified the following new interferants: acid phosphatase in serum by ibuprofen and theophylline; non-prostatic acid phosphatase in serum by cefoxitin and doxycycline; creatine kinase MB in serum by doxycycline; total bilirubin in serum (Jendrassik-Grof method) by rifampicin and intralipid; total bilirubin in serum (DPD method) by intralipid; creatinine in serum (Jaffe method) by cefoxitin; fructosamine in serum by levodopa and methyldopa; uric acid in serum by levodopa, methyldopa and tetracycline; carbamazepine in serum by doxycycline, levodopa, methyldopa and metronidazole; digitoxin in serum by rifampicin; phenytoin in serum by doxycycline, ibuprofen, metronidazole and theophylline; theophylline in serum by acetaminophen, cefoxitin, doxycycline, levodopa, phenylbutazone and rifampicin; tobramycin in serum by cefoxitin, doxycycline, levodopa, rifampicin and phenylbutazone; valproic acid in serum by phenylbutazone; C3 in serum by intralipid; C4 in serum by doxycycline; rheumatoid factor in serum by ibuprofen and metronidazole; pancreatic amylase and total amylase in urine by acetylcysteine, ascorbic acid, cefoxitin, gentamicin, levodopa, methyldopa and ofloxacin; magnesium in urine by acetylcysteine, gentamicin and methyldopa; beta2-microglobulin in urine by ascorbic acid; total protein in urine by ascorbic acid, Ca-dobesilate and phenylbutazone. Interference in acid phosphatase, creatine kinase MB and bilirubin methods was observed at very low analyte concentrations, and therefore it may not be evident at higher concentrations. The study confirmed the usefulness of the recommendation.