Influence of ethnicity on biochemical markers of health and disease in the CALIPER cohort of healthy children and adolescents.

Background Accurate pediatric reference intervals (RIs) for laboratory tests determined in a healthy pediatric population are essential for correct laboratory test interpretation and clinical decision-making. In pediatrics, RIs require partitioning by age and/or sex; however, the need for partitioning based on ethnicity is unclear. Here, we assessed the influence of ethnicity on biomarker concentrations in the Canadian Laboratory Initiative on Pediatric Reference Intervals (CALIPER) cohort of healthy children and adolescents and compared the results with the National Health and Nutrition Examination Survey (NHANES). Methods A total of 52 biomarkers were measured in a multiethnic population of 846-1179 healthy children (aged 5 to <19 years) upon informed consent. Biomarker concentrations were retrospectively compared between four major ethnic groups (i.e. Black, Caucasian, East Asian, and South Asian, determined by parental ethnicity). Retrospective results were verified prospectively using an additional 500 healthy pediatric samples with equal sample size across ethnicities. Ethnic-specific differences were assessed based on statistical significance and biological and analytical variations. Appropriate age-, sex-, and ethnic-specific RIs were calculated. Results Ethnic-specific differences were not observed for 34 biomarkers examined in the retrospective analysis, while 18 demonstrated statistically significant ethnic differences. Among these, seven analytes demonstrated ethnic-specific differences in the prospective analysis: vitamin D, amylase, ferritin, follicle-stimulating hormone (FSH), immunoglobulin A (IgA), immunoglobulin G (IgG), and immunoglobulin M (IgM). Analysis of select NHANES data confirmed CALIPER findings. Conclusions This is the first comprehensive Canadian pediatric study examining ethnic-specific differences in common biomarkers. While the majority of biomarkers did not require ethnic partitioning, ethnic-specific RIs were established for seven biomarkers showing marked differences. Further studies in other populations are needed to confirm our findings.

Impact of a common CV evaluation scheme on overall laboratory performance: 8-year experience of a large national proficiency testing program in Japan.

In proficiency testing (PT), it is difficult to set rational criteria for determining target values and allowable limits. In Japan, the largest national PT program has for the past 8 years used an evaluation scheme based on a "common coefficient of variation" (cCV) to overcome this difficulty. The cCV, the average within-method variation, is derived by one-way analysis of variance from data of peer groups after excluding those with large variations. A unit interval used for grading participants is obtained by multiplying the cCV by the peer-group mean which is computed using an iterative method featuring repeated removal of a large portion of the tails of the distribution and reinflation of the standard deviation (SD) to compensate for the trimming. The evaluation scheme gives a relatively better grade to those participants in peer groups with small CVs, compared to use of individual peer-group CVs. The scheme has expedited the transition to more reproducible methods, resulting in a notable overall improvement in laboratory performance. The cCV evaluation scheme is uniformly applicable to any analyte measured quantitatively. The iterative method, an integral part of the scheme, effectively precludes bias in the evaluation.

Serum amylase values in callitrichids.

We determined the amylase levels in serum samples from six callitrichid species. The normal serum amylase values for all of these species was within or higher than the normal human range. Amylase values higher than the normal range occurred not only in association with pancreatitis but also pyometra, bone fracture, abscesses, diabetes mellitus and gastrointestinal conditions leading to diarrhea. We concluded that although serum amylase activity may be helpful in diagnosing pancreatitis, it is, as in humans, not specific for this condition in callitrichids.

[In vitro studies of pancreatic enzyme substitution]. / In-vitro-Untersuchungen zur Pankreasenzymsubstitution.

In-vitro activity of 14 commercial pancreatin preparations, commonly used in the Federal Republic of Germany, were tested. All had been declared by their manufacturers to contain more than 6000 FIP (Fédération International Pharmaceutique) units of lipase and to be acid resistant. The declared lipase and amylase amounts were found to be present in 11 of the 14 preparations. Three of the 14 preparations, said to be acid resistant were found not to be so in buffer with falling pH values between 4.0 and 2.5, so that there occurred an, at times marked, loss of enzyme activity. Most noticeable was the poor solubility of most preparations at pH 6.6. Only three of the 14 liberated their total enzyme content within 60 minutes, as they should for theoretical reasons, based on the relatively short duodeno-cecal transit time.

Interlaboratory standardization of enzyme results: the Richmond project.

Three concentrations of proficiency monitoring material and two concentrations of secondary standard calibrating material were prepared and stored frozen. The materials were prepared in buffer containing amylase from human saliva, aspartate aminotransferase from human liver, creatine kinase from human muscle, human serum albumin (20 g/L), and cofactors. The proficiency monitoring material was assayed by 10 methods in nine laboratories for 15 days to establish baseline performance. Each laboratory then used the secondary standard calibrating material to calibrate their instruments' responses to that of a standardization method, and repeated the assay of the proficiency monitoring material for 15 days. For amylase before calibration, between-laboratory mean values for the three concentrations of proficiency monitoring material were 29% lower than the standardization method, and the between-laboratory CV was 28%. After calibration the mean amylase values were 4% lower and the CV was 6%. For aspartate aminotransferase, the pre-calibration between-laboratory mean values were 24% higher than the standardization method (CV 14%) but only 3% higher (CV 6%) after calibration. CK activity deteriorated at storage temperatures above -70 degrees C. This study demonstrates that, by using a common secondary standard, laboratories can improve calibration of enzyme results.

Suitability of control materials in the differential inhibition assay for human pancreatic and salivary amylase.

We investigated the behavior of 26 quality-control sera with the inhibitor method for differential amylase (EC 3.2.1.1) assay. We also studied the sensitivity to the wheat-derived inhibitor of pancreatic amylases from 10 different animals in comparison with human pancreatic and salivary amylase. The results indicate that only control materials containing human amylases can be measured accurately. The animal amylases (bovine, equine, porcine) used in many quality control sera are relatively insensitive to the inhibitor as compared with human pancreatic and salivary amylase.

Activity of human and nonhuman amylases on different substrates used in enzymatic kinetic assay methods--a pitfall in interlaboratory quality control.

Many commercial kits have been marketed recently for the determination of amylase activity in clinical specimens by enzymatic kinetic methods. Oligosaccharides (e.g., maltotetraose or maltopentaose) or limit dextrin are used as substrates. Hydrolysis of the substrate is coupled through a series of enzymes to convert NAD+ to NADH which is measured at 340 nm. Commercially available controls and standards for the amylase test consist of pooled human sera supplemented with human, porcine, or bovine amylase. The authors tested various control sera and standards by six commercial kits. Sera supplemented with porcine or bovine pancreatic amylase gave significantly lower values when assayed by methods using maltotetraose as substrate than when assayed by methods using maltopentaose or other oligosaccharides as substrate. Sera supplemented with human salivary amylase gave comparable results by five of the six methods. Results were comparable by all six methods for serum specimen supplemented with human pancreatic amylase. These kinetic methods are superior to the older amyloclastic, saccharogenic, or dye-coupled starch methods and are expected to gain popularity among clinical laboratories. The authors recommend that quality control programs designed to evaluate interlaboratory performances consider the use of human pancreatic amylase to supplement their serum specimens.

Isolation of amylolytic system of Aspergillus oryzae on DEAE amylum.

Studying isolation technique with DEAE amylum the method was found to be suitable for isolation of alpha-amylase. After determination of optimal conditions sorption curves were illustrated, from which the amount of DEAE amylum needed for 100% enzyme sorption from solutions of various activity and origin can be calculated. Preparation obtained shows high temperature stability and can be used in food industry and agriculture or after its elution in pharmacy. At the end of the paper laboratory isolation technique is described.