Pediatric Reference Intervals Research Articles

Pediatric indirect reference intervals for hemogram parameters derived from hospital data

Pediatric indirect reference intervals for hemogram parameters derived from hospital data

CLSI-based verification and de novo establishment of reference intervals for common biochemical assays in Croatian newborns.

This study aimed to examine whether the Canadian Laboratory Initiative on Pediatric Reference Intervals (CALIPER) reference intervals for 19 commonly used biochemical assays (potassium, sodium, chloride, calcium, magnesium, inorganic phosphorous, glucose, urea, creatinine, direct and total bilirubin, C-reactive protein (CRP), total protein, albumin, aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma-glutamyl transferase (GGT), alkaline phosphatase (ALP) and lactate dehydrogenase (LD)) could be applied to the newborn population of one Croatian clinical hospital. Reference interval verification was performed according to the CLSI EP28-A3c guidelines. Samples of healthy newborns were selected using the direct a posteriori sampling method and analyzed on the Beckman Coulter AU680 biochemical analyzer. If verification wasn't satisfactory, further procedure included de novo determination of own reference intervals by analyzing 120 samples of healthy newborns. After the first set of measurements, 14/19 tested reference intervals were adopted for use: calcium, inorganic phosphorous, glucose, urea, creatinine, total bilirubin, CRP, total protein, albumin, AST, ALT, GGT, ALP and LD. A second set of samples was tested for 5 analytes: potassium, sodium, chloride, magnesium and direct bilirubin. The verification results of the additional samples for sodium and chloride were satisfactory, while the results for potassium, magnesium and direct bilirubin remained unsatisfactory and new reference intervals were determined. The CALIPER reference intervals can be implemented into routine laboratory and clinical practice for the tested newborn population for most of the analyzed assays, while own reference intervals for potassium, magnesium and direct bilirubin have been determined.

Plasma lipids paediatric reference intervals: Indirect estimation using a large 14-year database.

Establishing direct reference intervals (RIs) for paediatric patients is a very challenging endeavour. Indirect RIs can address this problem, using existing clinical laboratory databases from real-world data research. Compared to the traditional direct method, the indirect approach is highly practical, widely applicable, and low-cost. Considering the relevance of dyslipidemia in the paediatric age, to provide better laboratory services to the local paediatric population, we established population-specific lipid RIs via data mining. Our laboratory information system was searched for cholesterol (TC), triglycerides (TG), low-density lipoprotein (LDL) and high-density lipoprotein (HDL) of patients aged less than 18 years, performed from January 2009 until December 2022. RIs were estimated using RefineR algorithm. Values from 215,594 patients were initially collected. After refining data on the basis of specific exclusion criteria that left 17,933 patients, we determined the RIs for each analyte, including corresponding 95% confidence interval (95% CI). Age and sex partitions were required for proper stratification of the heterogenous subpopulations. Age-related variations in TC and TG values were observed mainly in children until 5 years. RIs were defined for children less than 3 years and for those of 3-18 years. In our population, the obtained RIs were comparable with those of the literature, but the upper TG limit in subjects under the age of 3 (2.03 mmol/L with 95% CI: 1.45-2.86) was lower than that previously reported. Our RIs, necessary for paediatric lipid monitoring, are tailored to the serviced patient population as should be done whenever possible.

Establishing a pediatric reference interval for plasma calprotectin

Plasma calprotectin is a promising new biomarker of inflammatory activity and has been found to correlate well with clinical and endoscopic activity in children and adolescents with inflammatory bowel disease. A pediatric reference interval for plasma calprotectin has not been established for the Phadia 250 EliA™ Calprotectin fluoroenzyme immunoassay. In studies regarding pre-analytical properties, excellent precision and stability was found. However, sensitivity to hemolysis was demonstrated. We identified pediatric blood samples from apparently healthy children who were referred by their general practitioner for blood sampling including measurement of hemoglobin (Hb) and C-reactive protein (CRP). We excluded samples from children who had undergone additional blood sampling within 2 months before or after the index sample, if Hb was outside of local reference ranges or CRP levels were above the lower limit of the measuring interval (LLM), and any samples with a hemolysis above 0.02 mmol/L. Using this algorithm, we identified 141 blood samples. No outliers were identified. We established the following reference intervals according to CLSI C28-A3 using non-parametric statistics: 1–17 years: 16–246 µg/L. Our results may prove useful for further utilization of plasma calprotectin as a marker of inflammation in children and adolescents with inflammatory disorders.

Pediatric reference intervals for serum folate and cobalamin based on a European population without exposure to folic acid fortification

The aim of the present study was to define pediatric reference intervals for serum cobalamin and folate utilizing data generated from a population not exposed to food fortified with folic acid. Folate and cobalamin results analyzed by electrochemiluminescence immunoassay (Roche Cobas) were obtained from 2375 children (2 months to 17.99 years of age). The serum samples were collected between 2011 and 2015 as part of the LIFE (Leipzig Research Centre for Civilization Diseases) Child cohort study in Germany, where folic acid fortification of food is not mandated. These results were used to generate age- and gender-specific reference intervals presented as non-parametric 2.5 and 97.5 percentiles. Because of a subsequent restandardisation of the Roche folate assay in 2016, folate values were recalculated accordingly for adaptation to results obtained using the present calibration. In both genders, folate concentrations decreased continuously with age, whereas cobalamin concentrations peaked at five years of age and then declined. Teenage females had higher concentrations of cobalamin in the age group 12–17.99 years.

Reference intervals for serum 11-oxygenated androgens in children.

Classic androgens such as dehydroepiandrosterone, androstenedione, and testosterone are generally measured for diagnosis and treatment monitoring in children and adolescents with hyperandrogenism, as can occur in congenital adrenal hyperplasia, premature pubarche, or polycystic ovarian syndrome. However, adrenally-derived 11-oxygenated androgens also contribute to the androgen pool and should therefore be considered in clinical management. Nevertheless, paediatric reference intervals are lacking. Therefore, we developed a serum assay to establish reference intervals for four 11-oxygenated androgens in addition to four classic androgens. Reference interval study for serum 11-oxygenated androgens in children. We developed and validated a sensitive LC-MS/MS assay and quantified eight serum androgens, including four 11-oxygenated androgens, in serum of 256 healthy children (aged 0-17 years old). An age-dependency for all androgens was observed, and therefore we divided the cohort based on age (prepubertal (n=133; 94 boys, 39 girls) and pubertal (n=123; 52 boys, 71 girls)) to compute reference intervals (2.5th - 97.5th percentiles). In the prepubertal group, there was no significant sex-difference for any of the measured androgens. In the pubertal group, androstenedione, testosterone, and dihydrotestosterone showed a significant difference between boys and girls. In contrast, adrenal androgens dehydroepiandrosterone, 11-hydroxyandrostenedione, 11-ketoandrostenedione, 11-hydroxytestosterone, and 11-ketotestosterone did not. We developed and validated an assay for 11-oxygenated androgens, in addition to four classic androgens and established reference intervals. This enables a comprehensive evaluation of serum androgen status in children with clinical symptoms of hyperandrogenism.

Indirect estimation of pediatric reference interval via density graph deep embedded clustering

Establishing reference intervals (RIs) for pediatric patients is crucial in clinical decision-making, and there is a critical gap of pediatric RIs in China. However, the direct sampling technique for establishing RIs is resource-intensive and ethically challenging. Indirect estimation methods, such as unsupervised clustering algorithms, have emerged as potential alternatives for predicting reference intervals. This study introduces deep graph clustering methods into indirect estimation of pediatric reference intervals. Specifically, we propose a Density Graph Deep Embedded Clustering (DGDEC) algorithm, which incorporates a density feature extractor to enhance sample representation and provides additional perspectives for distinguishing different levels of health status among populations. Additionally, we construct an adjacency matrix by computing the similarity between samples after feature enhancement. The DGDEC algorithm leverages the adjacency matrix to capture the interrelationships between patients and divides patients into different groups, thereby estimating reference intervals for the potential healthy population. The experimental results demonstrate that when compared to other indirect estimation techniques, our method ensures the predicted pediatric reference intervals in different age and gender groups are closer to the true values while maintaining good generalization performance. Additionally, through ablation experiments, our study confirms that the similarity between patients and the multi-scale density features of samples can effectively describe the potential health status of patients.

A case for caution: Paediatric reference intervals for thyroid function tests

A case for caution: Paediatric reference intervals for thyroid function tests

Pediatric reference intervals for serum neurofilament light and glial fibrillary acidic protein using the Canadian Laboratory Initiative on Pediatric Reference Intervals (CALIPER) cohort.

Blood biomarkers have the potential to transform diagnosis and prognosis for multiple neurological indications. Establishing normative data is a critical benchmark in the analytical validation process. Normative data are important in children as little is known about how brain development may impact potential biomarkers. The objective of this study is to generate pediatric reference intervals (RIs) for serum neurofilament light (NfL), an axonal marker, and glial fibrillary acidic protein (GFAP), an astrocytic marker. Serum from healthy children and adolescents aged 1 to <19 years were obtained from the Canadian Laboratory Initiative on Pediatric Reference Intervals (CALIPER) cohort. Serum NfL (n=300) and GFAP (n=316) were quantified using Simoa technology, and discrete RI (2.5th and 97.5th percentiles) and continuous RI (5th and 95th percentiles) were generated. While there was no association with sex, there was a statistically significant (p<0.0001) negative association between age and serum NfL (Rho-0.400) and GFAP (Rho-0.749). Two statistically significant age partitions were generated for NfL: age 1 to <10 years (lower, upper limit; 3.13, 20.6 pg/mL) and 10 to <19 years (1.82, 7.44 pg/mL). For GFAP, three statistically significant age partitions were generated: age 1 to <3.5 years (80.4, 601 pg/mL); 3.5 to <11 years (50.7, 224 pg/mL); and 11 to <19 years (26.2, 119 pg/mL). Taken together with the literature on adults, NfL and GFAP display U-shaped curves with high levels in infants, decreasing levels during childhood, a plateau during adolescence and early adulthood and increasing levels in seniors. These normative data are expected to inform future pediatric studies on the importance of age on neurological blood biomarkers.

A survey of total IgE reference intervals reported by Scandinavian and British medical laboratories – a need for harmonisation

Objectives There appears to be marked discrepancies between total IgE reference intervals (RIs) in use by many laboratories and those recommended by published studies. The aim of this study was therefore to review total IgE RIs currently reported by Scandinavian and British laboratories and to compare these to published RIs identified by a literature review. Methods Relevant laboratories were identified by test directories provided by the national accreditation bodies in Norway, Sweden, Denmark and the UK. Total IgE RIs and their sources were acquired by accessing laboratory user handbooks or by an electronic survey. In addition a literature review of published total IgE RI studies was performed. Results From 172 accredited laboratories providing total IgE analysis, data was acquired from 122 laboratories. An adult upper reference limit between 81 to 150 kU/L was reported by 89% of these. Denmark and Sweden reported the most harmonised RIs whilst Norway and the UK exhibited the least degree of harmonisation. Published adult (n = 6) and paediatric (n = 6) RI studies reported markedly higher upper limits than those currently in use by the laboratories included in this study. There were also large variations in the number of age strata in use for paediatric RIs. Conclusion This study demonstrates large variations in currently utilised IgE RIs by Scandinavian and British accredited laboratories and most report markedly lower RIs than those recommended by recent RI publications. Many laboratories likely utilise outdated RIs and should consider critically reviewing and updating their RIs.

Paediatric reference intervals and curves for haemoglobin and ferritin: protocol for a systematic review and meta-analysis

IntroductionReference intervals and reference curves provide clinicians with a point of reference when evaluating patients’ laboratory test results. In practical applications, the 2.5th and 97.5th percentiles of healthy reference population...

A-335 Pediatric Cortisol Reference Intervals (RI): Impact of Age-Specific RI on the Rate of Abnormal “Low” Cortisol Results

Abstract Background Serum cortisol, measured by automated immunoassay, is a rapid test used for the initial assessment of adrenal dysfunction. Physiologic serum cortisol concentrations are influenced by many factors including diurnal variation, stress, and patient age. In the absence of established pediatric reference intervals (RIs), our laboratory has utilized adult RIs to flag pediatric cortisol results as abnormally high or low in the electronic health record. However, pediatric cortisol RIs recently defined by the Canadian Laboratory Initiative on Pediatric Reference Intervals (CALIPER) are considerably lower than the adult RIs currently in use. This could cause pediatric cortisol results to be incorrectly flagged as “low” when they are within the age-specific RI and lead to unnecessary follow-up testing. The aim of this study was to determine the impact of implementing CALIPER pediatric cortisol RIs on the rate of “low” result flagging for pediatric patients. Methods AM cortisol results for patients age &amp;lt;18 years reported between 10/2012- 09/2022 were obtained from the Mayo Clinic data repository. These results contained values measured by both Beckman Access (n = 3 818) and Roche Cobas (n = 625) immunoassays. Results classified as abnormal “low” by current adult RIs (Beckman: 7–25 mcg/dL, Roche: 4.8–20 mcg/dL) were compared to results which would flag low according to the appropriate method- and age-specific RIs defined by CALIPER (Beckman: 1-&amp;lt;13 yrs 2.19–12.8 mcg/dL, 13-&amp;lt;16 yrs 3.03–17.1 mcg/dL, 16-&amp;lt;19 yrs 3.78–19.4 mcg/dL; Roche: &amp;lt;1 yr 0.58–17.2 mcg/dL, 1-&amp;lt;12 yrs 2.39–14.9 mcg/dL, 12-&amp;lt;19 yrs 3.63–17.4 mcg/dL). The proportion of results flagging low by adult versus pediatric RI were compared by chi-squared test, with P &amp;lt; 0.05 considered significant. Results For Beckman, the percentages of pediatric patient cortisol results flagging low using the adult RI versus (vs) the pediatric age-specific RI were: 35% vs 7% for 1–12 years of age (P &amp;lt; 0.001, n = 1866), 22% vs 5% for 13–15 years (P &amp;lt; 0.001, n = 966), and 16% vs 5% for 16–18 years (P &amp;lt; 0.001, n = 986). For Roche, the same analysis yielded: 52% vs 9% for 0–1 years (P = 0.001, n = 23), 14% vs 8% for 1–11 years (P = 0.03, n = 238), and 9% vs 6% for 12–18 years (P = 0.16, n = 364). Conclusion The implementation of pediatric RIs for serum cortisol will have a significant impact on the number of “low” result flags for patient results on both Beckman and Roche platforms. Statistically significant decreases in the percentage of low result flags were observed on both platforms for all age ranges except for the age bracket of 12–18 years by Roche. Furthermore, pediatric RIs appeared to produce more consistent rates of abnormal results across methods and age ranges, with all groups flagging low at a rate of 5–9%, whereas the same age ranges with adult RIs flagged at rates ranging from 9–52%. Lowering the RIs for pediatric cortisol to more appropriate ranges as identified by CALIPER will decrease the number of “low” flag results. This has the potential to decrease unnecessary follow-up, including repeat testing and further diagnostic procedures such as ACTH stimulation testing. Implementation of pediatric RIs has potential benefits regarding stress and cost for patients and parents, alarm fatigue for physicians, and utilization of laboratory resources.

A-334 Investigation on Use of NHANES Data to Develop Continuous Pediatric Reference Intervals - Pilot Study with Hemoglobin

Abstract Background Accurate Pediatric Reference Intervals (PRIs) are critical for assessing health, diagnosing disease, and establishing treatment efficacy. A recent literature review established that current PRIs are inconsistent, and partitioning reference intervals into arbitrary age groups may conceal the underlying biochemistry of child development. To overcome these challenges, continuous PRIs derived using specimens collected with standardized procedures from a well-defined population were proposed. The National Health and Nutrition Examination Survey (NHANES) meets these criteria and could be used to provide accurate PRIs for public health and clinical community use. However, no U.S. studies have described developing continuous PRIs for biomarkers. This study investigates a potential approach to develop continuous hemoglobin PRIs with NHANES data. Methods Total hemoglobin values for children and adolescents 1–19 years from NHANES 2011–2018 were assessed. To exclude potentially abnormal hemoglobin values, individuals with diabetes, anemia, BMI &amp;gt;95th percentile, serum cotinine &amp;gt;10 ng/L, C-reactive protein &amp;gt;10 mg/dL, and self-reported tobacco use, or poor health were excluded. Hemoglobin values at the 5th, 50th, and 95th percentiles were estimated at 6-month increments of age for males and females using survey weights. Continuous curves over the age range were then generated using smoothing methods. Results The initial sample size was 16 315, of which 3 183 had missing hemoglobin values. After applying exclusions (n = 3 311), the final sample size was 9 821, of which 51.8% were males and 48.2% were females. Males had higher hemoglobin levels with a steeper slope in the curve over the age range and an increase in slope with adolescence, whereas hemoglobin levels in females peaked around age 12 before plateauing. Conclusion This investigation suggests that cross-sectional NHANES data can be used to develop continuous hemoglobin PRIs that reflect the physiologic changes commonly obscured by age group binning. More detailed assessments of appropriate sample exclusions and smoothing methods are underway.

The CELTIC ranges project (comprehensive and effective laboratory test reference intervals for Irish children) methodology and results for renal profile tests in plasma on the Roche modularTM system.

The CELTIC ranges project aims to deliver a comprehensive range of reference intervals for commonly ordered laboratory investigations suitable for use in an Irish population as well as enabling comparison with relevant international studies. In this paper, we describe our methodology used throughout the entire project and present paediatric reference intervals for renal profile tests in plasma (sodium, potassium, urea and creatinine). 1023 children aged up to 17years were recruited from our hospital's general practitioner paediatric phlebotomy clinic. Clinical chemistry analyses were performed on the Roche modular system and statistical analysis was completed in line with CLSI guideline EP28-A3c. The plasma reference interval for sodium for ages 0.45-16.99 years was 137-143mmol/L in 1000 subjects (combined genders). For plasma potassium, the corresponding ranges between 1 and 16.99years (combined genders) were 3.6-4.8mmol/L. Apart from neonates and in keeping with other studies, age partitioning for electrolytes was not required. Data for plasma creatinine (enzymatic methodology) and urea is also presented and, as anticipated, required partitioning for both age and gender. Our renal profile findings are broadly consistent with those of international studies, for example, CALIPER, HAPPI, NORDIC, PRINCE and KiGGs. Moreover, the CELTIC ranges study is also based on over 1000 subjects whose samples were analysed on the widely used Roche modular analytics system. We also expect the findings will improve knowledge of children's metabolic health in Ireland.

Pediatric reference intervals for endocrine markers in healthy children and adolescents on the Liaison XL (DiaSorin) immunoassay system

ObjectivesProminent physiological changes occurring throughout childhood and adolescence necessitate the consideration of age and sex in biomarker interpretation. Critical gaps exist in pediatric reference intervals (RIs) for specialized endocrine markers, despite expected influence of growth and development. The current study aimed to establish and/or verify RIs for six specialized endocrine markers on a specialized immunoassay system. MethodsSamples were collected from healthy children and adolescents (5 to <19 years) and apparently healthy outpatients (0 to <5 years) as part of the Canadian Laboratory Initiative on Pediatric Reference Intervals (CALIPER). Serum samples were analysed for aldosterone, renin (plasma), thyroglobulin, anti-thyroglobulin, growth hormone, and insulin-like growth factor-1 (IGF-1) on the Liaison XL (DiaSorin) immunoassay platform. RIs (2.5th and 97.5th percentiles) were established for aldosterone, renin, thyroglobulin, anti-thyroglobulin, and growth hormone. Manufacturer-recommended pediatric RIs for IGF-1 were verified. ResultsAge-specific RIs were established for aldosterone, renin, and thyroglobulin, while no age-specific differences were observed for anti-thyroglobulin or growth hormone. IGF-1 was the only endocrine marker studied that demonstrated significant sex-specific differences. Manufacturer-recommended IGF-1 RIs were verified for children aged 6 to <19 years, while those for children aged 0 to <6 years did not verify. ConclusionsThis study marks the first time that pediatric RIs for aldosterone and renin were established in the CALIPER cohort and highlights the dynamic changes that occur in water and sodium homeostasis during the first years of life. Overall, these data will assist pediatric clinical laboratories in test result interpretation and improve clinical decision-making for patients tested using Liaison immunoassays.

Pediatric reference intervals of the hemoglobin fractions HbA2, HbF and HbA0 using high-performance liquid chromatography and capillary electrophoresis

Introductionβ-thalassemia is a common genetic disorder with an estimated prevalence of 80–90 million carriers worldwide. As elevated hemoglobin A2 (HbA2) is a primary feature of carriers, hemoglobin fraction analysis is a common technique used for initial screening. However, pediatric reference intervals (RIs) are scarce. Hence, the aim was to establish pediatric RIs of hemoglobin fractions using high-performance liquid chromatography (HPLC) and capillary electrophoresis (CE). MethodsSamples were collected from assumed healthy children and adolescents of 1–18 years. Analyses were conducted using the Tosoh Automated Glycohemoglobin Analyzer HLC-723®G11 (Tosoh G11, HPLC) and the Capillarys 3 Octa (CE). Data were investigated for need of partitioning by both age (1–6 years vs. 6–18 years) and sex. ResultsIn total, 189 and 196 subjects were included in the statistical analysis of HPLC and CE, respectively. The 95% RI of HbA2 was 2.00–2.90% by HPLC and 2.2–3.0% by CE. Partitioning of data was not clinically relevant by HPLC. However, partitioning by age was suggested by CE. ConclusionRIs of hemoglobin fractions in individuals of 1–18 years using commercially available HPLC and CE equipment were reported. This is the first report of a pediatric RI of HbA2 using the Tosoh G11.

Neurofilament light chain: serum reference intervals in Danish children aged 0-17 years

Elevated levels of neurofilament light chain (NfL) in the blood is an unspecific biomarker for damage to neuronal axons. The measurement of NfL levels in the blood can provide useful information for monitoring and prognostication of various neurological disorders in children, but a reference interval (RI) is needed before the clinical implementation of the biomarker. We aimed to establish a RI for children aged 0–17 years. Serum samples from 292 healthy reference subjects aged 0.4–17.9 years were analysed by a single-molecule array (Simoa®) established for routine clinical use. Non-parametric quantile regression was used to model a continuous RI, and a traditional age-partitioned non-parametric RI was established according to Clinical and Laboratory Standard Institute (CLSI) guideline C28-A3. Furthermore, we investigated the effect of hemolysis on assay performance. The traditional age-partitioned non-parametric RI for the age group <3 years was 3.5–16.6 ng/L and 2.1–13.9 ng/L in the age group ≥3 years, respectively. The continuous RI showed an age-dependent decrease in median NfL levels in the first three years of life which was also evident in the age-partitioning of the traditional RI. We found no difference between sexes and no impact of hemolysis on the NfL test results. This study establishes a pediatric RI for serum NfL and lays the groundwork for its future use in clinical practice.

Pediatric reference intervals for hematology parameters in healthy infants and young children in Iran.

Defining accurate age- and sex-specific reference intervals (RIs) for hematology parameters, especially for the pediatric population, is important for making an appropriate clinical diagnosis. To address gaps, we established age-specific RIs for 11 hematologic parameters in Iranian children younger than 30 months for the first time. Fresh whole blood samples collected from a total of 344 participants (males: 158 and females: 186) ages 3 days to 30 months, with a mean age of 12.91 ± 7.15 months, were recruited from healthcare centers in Mashhad, Iran. Hematologic parameters, including complete blood count (CBC), were analyzed on the Sysmex auto-analyzer system (KX-21 N). RIs were calculated with 90% confidence intervals using the direct method based on CLSI Ep28-A3 and C28-A3 guidelines. None of the CBC parameters required sex partitioning. Of 11 CBC parameters, six required age partitions of 3 days-<4 months, 4-<10, 10-<15, and 4-<30 months. Five parameters (i.e., white blood cell count, mean corpuscular hemoglobin concentration, mean platelet volume, red cell distribution width, and platelet distribution width) did not demonstrate age-specific changes. RIs of red blood cell count and hematocrit, as well as hemoglobin, increased with age, while mean corpuscular volume, mean corpuscular hemoglobin, and platelet count, decreased with age. In this study, we established RIs for 11 hematology parameters in young children. Age partitioning was required for six parameters demonstrating marked changes during the early period of growth and development and necessitating the use of pediatric-specific reference standards.

Pediatric total fractionated metanephrines: age-related reference intervals in spot urine.

Sparse metanephrines reference intervals in pediatric populations are available and different study designs and technologies/ assays used in these studies lead to hardly transferable data from a laboratory to another. The aim of this study was to update pediatric reference intervals of total fractionated metanephrines in spot urine samples, using a commercial extraction kit run on a specific high-pressure liquid chromatograph coupled with an electrochemical detector. Four hundred and fifty-two spot pediatric urinary samples previously submitted to urinalysis were consecutively included in the study with the exclusion of children's samples with diagnosis or clinical suspicion of paraganglioma/pheochromocytoma, kidney diseases and arterial hypertension. Urinary metanephrine, normetanephrine and 3-methoxytyramine were extracted with ClinRep® HPLC Complete kit and run on HPLC Prominence liquid chromatograph LC-20AT (Shimadzu Italia S.r.l. Milan, Italy) coupled with Decade II electrochemical detector (Antec Scientific, Zoeterwoude, the Nederlands, provided by Alfatech S.r.l., Genoa, Italy). Results were expressed as the ratio analyte-to-creatinine. Any of the three analytes required a repartition by gender (metanephrine P=0.27; normetanephrine P=0.90 and 3-methoxytyramine P=0.18). A significant statistically inversely proportional relation with age was found for metanephrine (P<0.0001; ρ=-0.72), normetanephrine (P<0.0001; ρ=-0.75) and 3-methoxytyramine (P<0.0001; ρ=-0.83). Reference intervals were calculated as function of age. This study provides pediatric reference intervals for urinary fractionated total metanephrines in spot urine calibrated on a specific instrumentation and extraction commercial kit.

Dried blood spot reference intervals for 18 amino acids in a 1 to 6 years old pediatric cohort

ObjectivesReference intervals are indispensable for the accurate clinical interpretation of clinical laboratory tests. The reference intervals of amino acids in dried blood spots (DBS) from nonnewborn children are limited. In this study, we aim to establish the pediatric reference intervals for amino acids in DBS from healthy Chinese children aged from 1 to 6 years and to investigate the effect of sex and age. Design and MethodsIn 301 healthy subjects aged from 1 to 6 years old, eighteen DBS amino acids were determined using ultra-performance chromatography-tandem mass spectrometry method. Amino acid concentrations were examined in relation to sex and age. Reference intervals were established according to the CLSI C28-A3 guidelines. ResultsReference intervals of 18 amino acids bounded by the 2.5 and 97.5 percentiles were calculated in DBS specimen. No significant influence of age was observed for all the target amino acid concentrations in 1- to 6-year-olds. Sex differences were found in leucine and aspartic acid. ConclusionsThe RIs established in the present study added value for diagnosing and managing the amino acid-related diseases in the pediatric population.