Pediatric reference intervals for 34 biochemical analytes in urban school children and adolescents

Modeling calcium and magnesium balance: Regulation by calciotropic hormones and adaptations under varying dietary intake

Magnesium (Mg2+) is crucial for several cellular and physiological processes and is tightly regulated due to health risks associated with imbalances. Mg2+, calcium (Ca2+), parathyroid hormone, and vitamin D3 are tightly coupled, ensuring proper bone metabolism and intestinal and renal absorption of Mg2+ and Ca2+. While several Ca2+ homeostasis models exist, no computational model has been developed to study Mg2+ homeostasis. We developed a computational model of Mg2+ homeostasis in male rats, integrating it with an existing Ca2+ homeostasis model, to understand the interconnected physiological processes regulating their homeostasis. We then analyzed adaptations in these interconnected processes under (1) dietary Mg2+ deficiency, (2) low/high dietary Ca2+ with Mg2+ deficiency, and (3) vitamin D3 deficiency. Model simulations predicted severe hypomagnesemia and mild hypocalcemia with significant dietary Mg2+ deficiency. Low dietary Ca2+ improved, while high dietary Ca2+ worsened Mg2+ deficiency. Finally, vitamin D3 deficiency caused severe hypocalcemia, with minimal impact on Mg2+ homeostasis.

How the kidney regulates magnesium: a modelling study

The kidneys are crucial for maintaining Mg2+ homeostasis. Along the proximal tubule and thick ascending limb, Mg2+ is reabsorbed paracellularly, while along the distal convoluted tubule (DCT), Mg2+ is reabsorbed transcellularly via transient receptor potential melastatin 6 (TRPM6). TRPM6 and other renal transporter expressions are regulated by sex hormones. To investigate renal Mg2 handling, we have developed sex-specific computational models of electrolyte transport along rat superficial nephron. Model simulations indicated that along the proximal tubule and thick ascending limb, Mg2+ and Na+ transport occur parallelly, but they are dissociated along the DCT. In addition, our models predicted higher paracellular Mg2+ permeability in females to attain similar cortical thick ascending limb fractional Mg2+ reabsorption in both sexes. Furthermore, DCT fractional Mg2+ reabsorption is higher in females than in males, allowing females to better fine-tune Mg2+ excretion. We validated our models by simulating the administration of three classes of diuretics. The model predicted significantly increased, marginally increased and significantly decreased Mg2+ excretions for loop, thiazide and K-sparing diuretics, respectively, aligning with experimental findings. The models can be used to conduct in silico studies on kidney adaptations to Mg2+ homeostasis alterations during conditions such as pregnancy, diabetes and chronic kidney disease.

Establishment of reference intervals for serum amylase and lipase: a large sample study based on Chinese healthy children

This study aimed to establish age- and sex-specific reference intervals for serum amylase and lipase in children by prospective investigation. A total of 6466 healthy Han children of 1 month ∼ <18 years were recruited in communities and schools in five administrative regions of Jilin Province, China. The serum amylase and lipase concentrations were measured on the VITROS 5600 integrated system. The reference intervals were defined by a nonparametric 95% percentile interval. Reference intervals of amylase were divided into four age-specific partitions. It increased rapidly between the ages of 1 month ∼ <1 year and 1 ∼ <5 years, slightly decreased between the ages of 5 ∼ <12 years, and increased slowly between 12 ∼ <18 years. Lipase concentrations showed sex differences after 1-year-old, with reference intervals in males divided into 2 divisions and 3 divisions in females. The lipase concentrations in both males and females showed an upward trend, and the lipase concentrations in females were higher than those in males. This study established reference intervals for amylase and lipase in healthy Chinese children and provided a more accurate explanation for the diagnosis and prognosis of clinical pediatric diseases.

Establishment of reference intervals for serum amylase and lipase: a large sample study based on Chinese healthy children

This study aimed to establish age- and sex-specific reference intervals for serum amylase and lipase in children by prospective investigation. A total of 6466 healthy Han children of 1 month ∼ <18 years were recruited in communities and schools in five administrative regions of Jilin Province, China. The serum amylase and lipase concentrations were measured on the VITROS 5600 integrated system. The reference intervals were defined by a nonparametric 95% percentile interval. Reference intervals of amylase were divided into four age-specific partitions. It increased rapidly between the ages of 1 month ∼ <1 year and 1 ∼ <5 years, slightly decreased between the ages of 5 ∼ <12 years, and increased slowly between 12 ∼ <18 years. Lipase concentrations showed sex differences after 1-year-old, with reference intervals in males divided into 2 divisions and 3 divisions in females. The lipase concentrations in both males and females showed an upward trend, and the lipase concentrations in females were higher than those in males. This study established reference intervals for amylase and lipase in healthy Chinese children and provided a more accurate explanation for the diagnosis and prognosis of clinical pediatric diseases.

Normative range of blood biochemical parameters in urban Indian school-going adolescents

Adolescence is the most critical phase of human growth that radically alters physiology of the body and wherein any inconsistency can lead to serious health consequences in adulthood. The timing and pace at which various developmental events occur during adolescence is highly diverse and thus results in a drastic change in blood biochemistry. Monitoring the physiological levels of various biochemical measures in ample number of individuals during adolescence can call up for an early intervention in managing metabolic diseases in adulthood. Today, only a couple of studies in different populations have investigated blood biochemistry in a small number of adolescents however, there is no comprehensive biochemical data available worldwide. In view, we performed a cross-sectional study in a sizeable group of 7,618 Indian adolescents (3,333 boys and 4,285 girls) aged between 11–17 years to inspect the distribution of values of common biochemical parameters that generally prevails during adolescence and we observed that various parameters considerably follow the reported values from different populations being 3.56–6.49mmol/L (fasting glucose), 10.60–199.48pmol/L (insulin), 0.21–3.22nmol/L (C–peptide), 3.85–6.25% (HbA₁c), 2.49–5.54mmol/L (total cholesterol), 1.16–3.69mmol/L (LDL), 0.78–1.85mmol/L (HDL), 0.33–2.24mmol/L (triglycerides), 3.56–11.45mmol/L (urea), 130.01–440.15μmol/L (uric acid) and 22.99–74.28μmol/L (creatinine). Barring LDL and triglycerides, all parameters differed significantly between boys and girls (p< 0.001). Highest difference was seen for uric acid (p = 1.3 x10^-187) followed by C–peptide (p = 6.6 x10^-89). Across all ages during adolescence, glycemic and nitrogen metabolites parameters varied markedly with gender. Amongst lipid parameters, only HDL levels were found to be significantly associated with gender following puberty (p< 0.001). All parameters except urea, differed considerably in obese and lean adolescents (p< 0.0001). The present study asserts that age, sex and BMI are the essential contributors to variability in blood biochemistry during adolescence. Our composite data on common blood biochemical measures will benefit future endeavors to define reference intervals in adolescents especially when the global availability is scarce.

Magnesium Urinary Excretion in Diabetic Adolescents

Objective: to define peculiarities of urinary magnesium (Mg) excretion in diabetic adolecents; to elucidate gender-related differences in Mg urinary excretion; to determine urinary Mg excretion differences between diabetic and age-matched healthy children. The diurnal, nocturnal and 24–h urinary Mg level in adolescent boys and girls (aged 13–17 years) with type I diabetes mellitus (DM) and in age-matched control groups of healthy boys and girls was examined. Additionally the adolescent girls were examined during different phases of their menstrual cycle. Results: Diurnal, overnight and 24–h Mg urinary excretion in diabetic adolescent boys and girls was significantly higher than in healthy ones. In diabetic boys 24 h Mg excretion was higher than in diabetic girls (4.59±1.4 vs. 3.34±1.5 mmol; p<0.05). The investigation showed gender-related differences in Mg urinary excretion in healthy adolescents: 24–h Mg urinary excretion was significantly higher in boys than in girls (2.66±0.9 vs. 2.1±0.9 mmol; p<0.05). The level of Mg in the nocturnal urine of boys and girls was significantly higher than in diurnal. Urine Mg was negatively related to height in adolescent girls. Conclusion: Diabetic adolescents excrete significantly more Mg with urine as compared to healthy ones.

Pediatric reference intervals for alkaline phosphatase

BACKGROUND

Interpretation of alkaline phosphatase activity in children is challenging due to extensive changes with growth and puberty leading to distinct sex- and age-specific dynamics. Continuous percentile charts from birth to adulthood allow accurate consideration of these dynamics and seem reasonable for an analyte as closely linked to growth as alkaline phosphatase. However, the ethical and practical challenges unique to pediatric reference intervals have restricted the creation of such percentile charts, resulting in limitations when clinical decisions are based on alkaline phosphatase activity.

METHODS

We applied an indirect method to generate percentile charts for alkaline phosphatase activity using clinical laboratory data collected during the clinical care of patients. A total of 361,405 samples from 124,440 patients from six German tertiary care centers and one German laboratory service provider measured between January 2004 and June 2015 were analyzed. Measurement of alkaline phosphatase activity was performed on Roche Cobas analyzers using the IFCC's photometric method.

RESULTS

We created percentile charts for alkaline phosphatase activity in girls and boys from birth to 18 years which can be used as reference intervals. Additionally, data tables of age- and sex-specific percentile values allow the incorporation of these results into laboratory information systems.

CONCLUSIONS

The percentile charts provided enable the appropriate differential diagnosis of changes in alkaline phosphatase activity due to disease and changes due to physiological development. After local validation, integration of the provided percentile charts into result reporting facilitates precise assessment of alkaline phosphatase dynamics in pediatrics.

Perspective: The Case for an Evidence-Based Reference Interval for Serum Magnesium: The Time Has Come

The 2015 Dietary Guidelines Advisory Committee indicated that magnesium was a shortfall nutrient that was underconsumed relative to the Estimated Average Requirement (EAR) for many Americans. Approximately 50% of Americans consume less than the EAR for magnesium, and some age groups consume substantially less. A growing body of literature from animal, epidemiologic, and clinical studies has demonstrated a varied pathologic role for magnesium deficiency that includes electrolyte, neurologic, musculoskeletal, and inflammatory disorders; osteoporosis; hypertension; cardiovascular diseases; metabolic syndrome; and diabetes. Studies have also demonstrated that magnesium deficiency is associated with several chronic diseases and that a reduced risk of these diseases is observed with higher magnesium intake or supplementation. Subclinical magnesium deficiency can exist despite the presentation of a normal status as defined within the current serum magnesium reference interval of 0.75-0.95 mmol/L. This reference interval was derived from data from NHANES I (1974), which was based on the distribution of serum magnesium in a normal population rather than clinical outcomes. What is needed is an evidenced-based serum magnesium reference interval that reflects optimal health and the current food environment and population. We present herein data from an array of scientific studies to support the perspective that subclinical deficiencies in magnesium exist, that they contribute to several chronic diseases, and that adopting a revised serum magnesium reference interval would improve clinical care and public health.

Standardization in laboratory medicine: Adoption of common reference intervals to the Croatian population

Considering the fact that the results of laboratory tests provide useful information about the state of health of patients, determination of reference value is considered an intrinsic part in the development of laboratory medicine. There are still huge differences in the analytical methods used as well as in the associated reference intervals which could consequently significantly affect the proper assessment of patient health. In a constant effort to increase the quality of patients’ care, there are numerous international initiatives for standardization and/or harmonization of laboratory diagnostics in order to achieve maximum comparability of laboratory test results and improve patient safety. Through the standardization and harmonization processes of analytical methods the ability to create unique reference intervals is achieved. Such reference intervals could be applied globally in all laboratories using methods traceable to the same reference measuring system and analysing the biological samples from the populations with similar socio-demographic and ethnic characteristics. In this review we outlined the results of the harmonization processes in Croatia in the field of population based reference intervals for clinically relevant blood and serum constituents which are in accordance with ongoing activity for worldwide standardization and harmonization based on traceability in laboratory medicine.

Hyperuricemia and Progression of CKD in Children and Adolescents: The Chronic Kidney Disease in Children (CKiD) Cohort Study

BACKGROUND

Hyperuricemia is associated with essential hypertension in children. No previous studies have evaluated the effect of hyperuricemia on progression of chronic kidney disease (CKD) in children.

STUDY DESIGN

Prospective observational cohort study.

SETTING & PARTICIPANTS

Children and adolescents (n=678 cross-sectional; n=627 longitudinal) with a median age of 12.3 (IQR, 8.6-15.6) years enrolled at 52 North American sites of the CKiD (CKD in Children) Study.

PREDICTOR

Serum uric acid level (<5.5, 5.5-7.5, and >7.5mg/dL).

OUTCOMES

Composite end point of either >30% decline in glomerular filtration rate (GFR) or initiation of renal replacement therapy.

MEASUREMENTS

Age, sex, race, blood pressure status, GFR, CKD cause, urine protein-creatinine ratio (<0.5, 0.5-<2.0, and ≥2.0mg/mg), age- and sex-specific body mass index > 95th percentile, use of diuretics, and serum uric acid level.

RESULTS

Older age, male sex, lower GFR, and body mass index > 95th percentile were associated with higher uric acid levels. 162, 294, and 171 participants had initial uric acid levels < 5.5, 5.5 to 7.5, or >7.5 mg/dL, respectively. We observed 225 instances of the composite end point over 5 years. In a multivariable parametric time-to-event analysis, compared with participants with initial uric acid levels < 5.5mg/dL, those with uric acid levels of 5.5 to 7.5 or >7.5mg/dL had 17% shorter (relative time, 0.83; 95% CI, 0.62-1.11) or 38% shorter (relative time, 0.62; 95% CI, 0.45-0.85) times to event, respectively. Hypertension, lower GFR, glomerular CKD cause, and elevated urine protein-creatinine ratio were also associated with faster times to the composite end point.

LIMITATIONS

The study lacked sufficient data to examine how use of specific medications might influence serum uric acid levels and CKD progression.

CONCLUSIONS

Hyperuricemia is a previously undescribed independent risk factor for faster progression of CKD in children and adolescents. It is possible that treatment of children and adolescents with CKD with urate-lowering therapy could slow disease progression.

Impact of the superoxide dismutase 2 Val16Ala polymorphism on the relationship between valproic acid exposure and elevation of γ-glutamyltransferase in patients with epilepsy: a population pharmacokinetic-pharmacodynamic analysis

BACKGROUND

There has been accumulating evidence that there are associations among γ-glutamyltransferase (γ-GT) elevation and all-cause mortality, cardiovascular diseases and metabolic diseases, including nonalcoholic fatty liver disease. The primary objective of this study was to evaluate the impact of the most common and potentially functional polymorphisms of antioxidant enzyme genes, i.e. superoxide dismutase 2 (SOD2), glutathione S-transferase M1 and glutathione S-transferase T1, on the γ-GT elevation during valproic acid (VPA) therapy.

METHODS AND FINDINGS

This retrospective study included 237 and 169 VPA-treated Japanese patients with epilepsy for population pharmacokinetic and pharmacokinetic-pharmacodynamic analyses, respectively. A nonlinear mixed-effect model represented the pharmacokinetics of VPA and the relationships between VPA exposure and γ-GT elevation. A one-compartment model of the pharmacokinetic parameters of VPA adequately described the data; while the model for the probability of the γ-GT elevation was fitted using a logistic regression model, in which the logit function of the probability was a linear function of VPA exposure. The SOD2 Val16Ala polymorphism and complication with intellectual disability were found to be significant covariates influencing the intercept of the logit function for the probability of an elevated γ-GT level. The predicted mean percentages of the subjects with γ-GT elevation were about 2- to 3-fold, 3- to 4-fold and 4- to 8-fold greater in patients with the SOD2 Val/Val genotype but without any intellectual disability, those with the SOD2 Val/Ala or Ala/Ala genotype and intellectual disability and those with the SOD2 Val/Val genotype and intellectual disability, respectively, compared to those with the SOD2 Val/Ala or Ala/Ala genotype without intellectual disability.

CONCLUSION

Our results showed that the SOD2 Val16Ala polymorphism has an impact on the relationship between VPA exposure and γ-GT elevation in patients with epilepsy. These results suggest that determining the SOD2 genotype could be helpful for preventing the VPA-induced γ-GT elevation.

Establishing pediatric reference intervals for 13 biochemical analytes derived from normal subjects in a pediatric endocrinology clinic in Korea

OBJECTIVES

Defining pediatric reference intervals is one of the most difficult tasks for laboratory physicians. The continuously changing physiology of growing children makes their laboratory values moving targets. In addition, ethnic and behavioral differences might also cause variations. The aim of this study was to establish age- and sex-specific partitioned reference intervals for 13 serum biochemical analytes in Korean children.

DESIGN AND METHODS

A total of 2474 patients, girls aged 2-14 years and boys aged 2-16 years, who underwent a short stature workup but were diagnosed as normal at the Pediatric Endocrinology Clinic of Severance Hospital (Seoul, Korea) between September 2010 and June 2012 were included in this study. The levels of serum calcium, inorganic phosphorus, blood urea nitrogen, creatinine, uric acid, glucose, total cholesterol, total protein, albumin, alkaline phosphatase, aspartic aminotransferase, alanine aminotransferase, and total bilirubin were measured using a Hitachi 7600 analyzer (Hitachi High-Technologies Corporation, Tokyo, Japan). Reference intervals were partitioned according to sex or age subgroups using the Harris and Boyd method.

RESULTS

Most analytes except calcium and albumin required partitioning either by sex or age. Age-specific partitioned reference intervals for alkaline phosphatase, creatinine, and total bilirubin were established for both males and females after being partitioned by sex. Additional age-specific partitioning of aspartic aminotransferase in females and total protein and uric acid in males was also required. Inorganic phosphorus, total cholesterol, alanine aminotransferase, blood urea nitrogen, and glucose were partitioned only by sex.

CONCLUSIONS

This study provided updated age- and sex-specific pediatric reference intervals for 13 basic serum chemistry analytes from a sufficient number of healthy children by using a modern analytical chemistry platform.

Estimating reliable paediatric reference intervals in clinical chemistry and haematology

Very few high-quality studies on paediatric reference intervals for general clinical chemistry and haematology analytes have been performed. Three recent prospective community-based projects utilising blood samples from healthy children in Sweden, Denmark and Canada have substantially improved the situation.

CONCLUSION

The present review summarises current reference interval studies for common clinical chemistry and haematology analyses.

Correlation of UGT1A1 TATA-box polymorphism and jaundice in breastfed newborns-early presentation of Gilbert's syndrome

OBJECTIVE

The etiology of jaundice in otherwise healthy breastfed newborns that can present as early-onset exaggerated physiologic jaundice, or late breast milk jaundice (BMJ), is not yet entirely understood. This study tested the hypothesis that molecular marker for Gilbert's syndrome (GS), UGT1A1 TATA-box polymorphism, is associated with this disorders.

METHODS

We have investigated the UGT1A1 polymorphism frequency and its relation to severity of hyperbilirubinemia and jaundice duration among 220 exclusively breastfed term newborns; 57 of them with non-physiologic hyperbilirubinemia (NH), and 163 with BMJ, and in 187 healthy controls.

RESULTS

Significant differences in TA7/7 genotype frequency were established. The highest frequency was observed among the newborns with BMJ (42.0%), intermediate in the NH group (24.6%), while the controls had the lowest TA7/7 frequency (12.8%). Linear increase in TA7/7 frequency was observed depending on the duration of jaundice, peaking at 42.4% in newborns with the longest jaundice duration. Positive correlation between the serum bilirubin levels and the TATA-box length was established in all groups.

CONCLUSION

This study provides evidence that UGT1A1 TATA-box polymorphism is an important risk factor for developing jaundice in term breastfed newborns, presented as either early non-physiologic hyperbilirubinemia or breast milk jaundice. These results further support the original Odell's idea of neonatal jaundice as an early presentation of GS.

First National Report on Aminotransaminases' Percentiles in Children of the Middle East and North Africa (MENA): the CASPIAN-III Study

BACKGROUND

By the current global obesogenic environment, non-alcoholic fatty liver disease is becoming an important health problem in the pediatric age group.

OBJECTIVES

This study aimed to determine the first age-and gender-specific percentiles and upper limit normal limit (ULN) of alanine aminotransaminase (ALT) and aspartate aminotransaminase (AST) among a nationally-representative sample of children and adolescents in the Middle East and North Africa (MENA). The second objective was to determine the linear association of obesity indexes and age with serum ALT and AST levels.

PATIENTS AND METHODS

This nationwide study was conducted among a representative sample of 4078 students aged 10-18 years, who were selected by multistage random cluster sampling from 27 provinces of Iran. ALT and AST were measured on fresh sera. Body mass index (BMI) was calculated as an index of generalized obesity, and waist- to- height ratio (WHtR) as an index of abdominal obesity. The age- and gender-specific percentiles of ALT and AST were constructed, and the 95th percentile of each enzyme was considered as the ULN. Gender-specific linear regression analysis was employed to examine the association of BMI or WHtR with the levels of ALT and AST.

RESULTS

Data of ALT and AST were available for 4078 (2038 girls) and 4150 (2061 girls),respectively. Participants had a mean (SD) age of 14.71 (2.41).The ULN of ALT for boys, girls,and the total individuals were 36.00; 38.00; and, 37.00 U/L, respectively. In both genders, ALT and AST had linear association with age. The association with BMI was significant for ALT in both genders and for AST only in boys, the association of ALT with WHtR was significant in both genders; the corresponding figures were not significant for AST.

CONCLUSIONS

The findings of the current study confirmed the current ULN value of 40 U/L commonly used for the pediatric age group. The linear association of indexes for generalized and abdominal obesity with ALT underscores the importance of timely prevention and control of childhood obesity.

Reference intervals on the Abbot Architect for serum thyroid hormones, lipids and prolactin in healthy children in a population-based study

Pediatric reference intervals for thyroid hormones, prolactin and lipids are of high clinical importance as deviations might indicate diseases with serious consequences. In general, previous reference intervals are hampered by the inclusion of only hospital-based populations of children and adolescents. The study included 694 children, evenly distributed from 6 months to 18 years of age. They were recruited as volunteers at child care units and schools. All subjects were apparently healthy and a questionnaire on diseases and medications was filled out by parents and by the older children. TSH, free T4, free T3, total cholesterol, LDL, HDL, triglycerides and prolactin were analyzed on Abbott Architect ci8200. Age- and gender-related 2.5 and 97.5 percentiles were estimated. The thyroid hormone levels were similar to previous data for the Abbott Architect platform, but exhibited differences from studies performed with other methods. Prolactin displayed wide reference ranges, but relatively small age-related changes, and a marginal difference between sexes during adolescence. Reference intervals for lipids in the different age groups are known to vary geographically. Levels of LDL and total cholesterol were higher than those reported for children in Canada, but lower than those reported for children in China. The study gives age- and gender- specific pediatric reference intervals, measured with modern methods for a number of important analytes. The results presented here differ from previously recommended reference intervals. In many earlier studies, retrospective hospital-based reference intervals, which may include various sub-groups have been presented. By non-hospital studies it is possible to avoid some of these biases.

Pediatric reference values for serum magnesium levels in Iranian subjects

Magnesium (Mg), an essential element, plays important roles in many physiological functions. Mg deficiency is associated with insulin resistance, cardiovascular disease, and disorders of the nervous system. The aim of this study was to determine reference values for serum Mg concentration in pediatrics. Serum Mg level was measured by flame atomic absorption spectrophotometry in 306 subjects (141 boys and 165 girls), aged 3-19 years, selected from among participants of the Tehran Lipid and Glucose Study. The International Federation of Clinical Chemistry guidelines (IFCC) and the robust method were used for determining reference values for sample sizes greater or less than 120 subjects respectively. The 95% reference values for serum Mg concentrations were 0.76-1.0, 0.75-1.0, and 0.76-0.99 mmol/L in boys, girls, and the all subjects respectively. According to the reference values obtained in this study, the prevalences of hypo- and hypermagnesemia, were 5.9% and 5.6% respectively. In conclusion, the current study presents pediatric reference values for serum Mg levels derived from a randomly selected healthy population, values which could be instrumental in detecting serum Mg abnormalities.

Applicability of common reference intervals for serum creatinine concentrations to the Croatian population

BACKGROUND

In accordance with an ongoing activity for worldwide harmonization based on traceability in laboratory methods, the goal of this study was to validate the applicability of recommended "common" reference intervals for serum creatinine concentrations using a specific enzymatic method to the Croatian population.

METHODS

The reference group consisted of 240 healthy subjects (120 males and 120 females), between 18 and 74 years of age (median 57 years), who were selected in accordance with the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) recommendations. Creatinine in serum was measured using the creatinine enzymatic assay (Olympus OSR61204) that was standardized to the isotopic dilution mass spectrometry (IDMS) method and National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 967. In addition, creatinine was measured using a kinetic Jaffe method (Olympus OSR6178) standardized to NIST SRM 909b level 2 standard.

RESULTS

Method comparison between enzymatic creatinine (x) and the Jaffe kinetic method (y) gave the following P/B equation for the entire group (n=240): y=1.00x+17.00; r=0.968. Reference intervals for serum creatinine (central 95th percentiles) obtained using the enzymatic creatinine method ranged from 54 to 107 micromol/L for males and from 50 to 93 micromol/L for females. The IFCC recommended common reference intervals for global applications are 64-104 micromol/L and 49-90 micromol/L for males and females, respectively.

CONCLUSIONS

Comparability of obtained results confirmed the applicability of recently recommended "common" reference intervals to the Croatian population for all laboratories measuring serum creatinine concentrations using enzymatic methods traceable to the IDMS method and NIST SRM 967.

Serum lipids, glucose and insulin levels in healthy schoolchildren aged 9 and 15 years from central Sweden: Reference values in relation to biological, social and lifestyle factors

BACKGROUND

There is a shortage of reference values for cardiovascular risk factors such as serum lipids, glucose and insulin related to biological, social and lifestyle factors for Swedish children and adolescents. Such values are needed for planning and evaluation of public health activities, and for clinical use.

DESIGN AND METHODS

Data for this cross-sectional, school-based study were collected during a school year (September to May). A random sample of 1137 girls and boys aged 9 and 15 years from two locations in central Sweden participated in the study, and blood samples were taken from 969 of them.

METHODS

Fasting serum blood samples were analysed for triglycerides, total cholesterol, high-density lipoprotein cholesterol, glucose and insulin. Physical examination included measurement of height, weight and pubertal status. Questionnaires provided family background data. Total physical activity was measured by accelerometer registration.

RESULTS

Serum levels differed significantly between age and gender groups and were correlated to pubertal status. Neither genetic nor socio-economic background nor smoking status influenced the serum levels. Insulin levels were elevated in subjects with a body mass index in the highest decentile, compared with the levels in the rest of the subjects. The insulin levels were inversely associated with total physical activity, and physical activity varied with season.

CONCLUSIONS

Pubertal status (biological age) should to be considered in the interpretation of serum values in schoolchildren rather than chronological age. The interpretation of insulin values should include both body mass index and physical activity level, and perhaps also season. Previously described regional differences in serum lipid levels in Swedish adults seem to be present also in children.

Pediatric reference intervals for lipids and apolipoproteins on the VITROS 5,1 FS Chemistry System

OBJECTIVES

Lipid biomarkers are integral in the assessment of dyslipidemia and cardiovascular risk, conditions that have become increasingly prevalent in pediatric populations. A comprehensive set of pediatric reference intervals for traditional or recently established lipid analytes is not currently available.

DESIGN AND METHODS

525 outpatient samples from a pediatric population were categorized into five age groups ranging from 0 to 20 years of age. Groups were further partitioned by gender. Serum or plasma samples were analyzed on the VITROS 5,1 FS Chemistry System for cholesterol and triglycerides by dry-film methods, direct HDL-C and LDL-C by selective detergent elimination, and apolipoproteins AI and B by immunoturbidimetry. Reference intervals were established by non-parametric methods at the 2.5th and 97.5th percentiles.

RESULTS

Lipid levels show age- and gender-related differences, particularly during the first year of life and in young adults following puberty. Concentrations of total cholesterol, LDL-C, and apo B were lowest in the 12 months after birth and remained relatively constant throughout childhood, but decreased for males in early adulthood. Triglyceride levels increased gradually throughout childhood and adolescence, and along with cholesterol, the upper limits of these intervals exceeded the recommended concentrations of lipid levels in children. For HDL-C and apo AI, no age- or sex-related differences were found until after puberty when values for males decreased slightly.

CONCLUSIONS

Our current reference intervals in children and adolescents provide an important update for lipid markers and suggest earlier incidence of hypercholesterolemia when compared to previous ranges. Increased profiling of lipids is anticipated, and these will aid in the early assessment of cardiovascular risk in pediatric populations.

Serum bilirubin levels in the U.S. population: gender effect and inverse correlation with colorectal cancer

Bilirubin, the primary end product of heme catabolism, is a key marker of liver and hematological disorders, and important cytoprotective properties have been ascribed to this bile pigment. The Third National Health and Nutrition Examination Survey, a comprehensive assessment of health and nutrition in the United States, was analyzed to determine the demographics and correlates of serum bilirubin levels in the general population. Men and women aged 17 and older were included in the weighted analysis, representing a total of 176,748,462 subjects. The mean serum total bilirubin in the adult population is 0.62 +/- 0.003 mg/dL (SEM), with a 97.5% cut-off of 1.4 mg/dL. Serum bilirubin levels are significantly higher in men (0.72 +/- 0.004) than in women (0.52 +/- 0.003 mg/dL) and are lower in non-Hispanic blacks (0.55 +/- 0.005 mg/dL) compared with non-Hispanic whites (0.63 +/- 0.004 mg/dL) and Mexican Americans (0.61 +/- 0.005 mg/dL). Bilirubin concentrations are unrelated to body weight but are reduced in active smokers. Individuals with a history of nondermatological malignancy exhibit significantly lower serum bilirubin concentrations compared with those who do not have a history of nondermatological cancer. In particular, each 1-mg/dL increase in serum bilirubin is associated with a markedly decreased prevalence of colorectal cancer (OR = 0.257; 95% CI 0.254-0.260). In conclusion, serum bilirubin levels vary significantly with gender, race, and smoking status. The observed inverse correlation between serum bilirubin concentrations and a history of nondermatological malignancy, particularly colorectal cancer, warrants further investigation of a potentially important chemopreventive function of bilirubin.

Hematology and blood biochemistry in infant baboons (Papio hamadryas)

Although published normative reference standards for hematologic and clinical chemistry measures are available for adult baboons, their applicability to infants has not been addressed. We analyzed these measures in 110 infant baboons (55 females and 55 males) from a large breeding colony at the Southwest Regional Primate Research Center in San Antonio, Texas. The sample consists of olive baboons and olive/yellow baboon hybrids, 1 week to 12 months of age. We produced cross-sectional reference values and examined the effects of age, sex, and subspecies on these variables. Hematology reference ranges for infant baboons are similar to, but wider than, those for adults. Reference ranges for blood biochemistry measures are generally more dissimilar to adults, indicating that for many variables, reference ranges for adult baboons are not adequate for infants. Although sex and subspecies differences are rare, age accounts for more than 10% of the variance in many of the variables.