A prospective, cross-sectional study to establish age-specific reference intervals for neonates and children in the setting of clinical biochemistry, immunology and haematology: the HAPPI Kids study protocol

Discovery of Alpha-1-Antichymotrypsin as a Marker of Delayed Recovery from Concussion in Children

Of the four million children who experience a concussion each year, 30-50% of children will experience delayed recovery, where they will continue to experience symptoms more than two weeks after their injury. Delayed recovery from concussion encompasses emotional, behavioral, physical, and cognitive symptoms, and as such, there is an increased focus on developing an objective tool to determine risk of delayed recovery. This study aimed to identify a blood protein signature predictive of delayed recovery from concussion in children. Plasma samples were collected from children who presented to the Emergency Department at the Royal Children's Hospital, Melbourne, within 48h post-concussion. This study involved a discovery and validation phase. For the discovery phase, untargeted proteomics analysis was performed using single window acquisition of all theoretical mass spectra to identify blood proteins differentially abundant in samples from children with and without delayed recovery from concussion. A subset of these proteins was then validated in a separate participant cohort using multiple reaction monitoring and enzyme linked immunosorbent assay. A blood protein signature predictive of delayed recovery from concussion was modeled using a Support Vector Machine, a machine learning approach. In the discovery phase, 22 blood proteins were differentially abundant in age- and sex-matched samples from children with (n = 9) and without (n = 9) delayed recovery from concussion, six of whom were chosen for validation. In the validation phase, alpha-1-ACT was shown to be significantly lower in children with delayed recovery (n = 12) compared with those without delayed recovery (n = 28), those with orthopedic injuries (n = 7) and healthy controls (n = 33). A model consisting of alpha-1-ACT concentration stratified children based on recovery from concussion with an 0.88 area under the curve. We have identified that alpha-1-ACT differentiates between children at risk of delayed recovery from those without delayed recovery from concussion. To our knowledge, this is the first study to identify alpha-1-ACT as a potential marker of delayed recovery from concussion in children. Multi-site studies are required to further validate this finding before use in a clinical setting.

LMS-based continuous reference percentiles for 14 laboratory parameters in the CALIPER cohort of healthy children and adolescents

OBJECTIVES

Marked physiological changes in growth and development present challenges in defining pediatric reference intervals for biomarkers of health and disease. Lambda, Mu, and Sigma (LMS)-based statistical modeling provides a continuous normal distribution by negating skewness and variation, and is commonly used to establish growth charts. Such LMS reference curves are suggested to enhance laboratory test result interpretation. The current study establishes LMS-based continuous reference percentiles for 14 biomarkers in the CALIPER cohort of healthy children and adolescents.

METHODS

Data from healthy children and adolescents aged 1-<19 years were used to establish continuous reference percentiles using a novel LMS-based statistical method, including 2.5th, 25th, 50th, 75th, and 97.5th percentiles. The LMS approach applies a Box-Cox data transformation and summarizes continuous distributions by age via three curves: skewness (Lambda), median (Mu), and coefficient of variation (Sigma).

RESULTS

LMS-based percentiles and z-scores were generated for 14 common pediatric biomarkers that demonstrate dynamic concentration patterns with age (e.g., alkaline phosphatase) and/or wherein the magnitude of difference from the population mean may be clinically relevant (e.g., triglycerides). The LMS model captured age- and sex-specific distributions accurately and was not substantially influenced by outlying points.

CONCLUSIONS

This is the first study to establish LMS-based continuous reference percentiles for biochemical markers in a healthy Canadian pediatric population. The current LMS-based approach builds upon previous continuous reference interval models by providing graded percentiles to improve test result interpretation, particularly with repeated measures over time. This method may assist in facilitating a patient-centered approach to laboratory medicine.

Age partitioned and continuous upper reference limits for Ortho VITROS High Sensitivity Troponin I in a healthy paediatric cohort

OBJECTIVES

In adults, the elevation of cardiac troponin (cTn) above the 99th percentile upper reference limit defines myocardial injury. The use and interpretation of cTn in a paediatric population, however, is difficult given the 99th percentile for different assays is not well established. Using paediatric blood samples from healthy neonates, infants and children we derived continuous and partitioned 97.5th and 99th percentiles for the Ortho VITROS hs-TnI assay.

METHODS

A total of 328 samples for infants, children and adolescents aged 0-17.8 years were obtained. Age partitioned reference limits were derived in accordance with CLSI EP28-A3C. Continuous reference limits were established as described previously by the HAPPI Kids Study team.

RESULTS

hs-TnI as measured by the Ortho VITROS Assay is highly elevated above the adult 99th percentile at birth and declines to lower levels within the first 6 months of life. The 99th centile upper reference limit for ages 0-3 months was 72 ng/L (90% CI: 52-91) and 9 ng/L (90% CI: 5.2-17.4) for ages 3 months to 18 years. Continuous upper 99th centile reference limits were comparable.

CONCLUSIONS

Partitioned and continuous 99th percentiles for hs-TnI were derived for the new Ortho VITROS assay in healthy neonates and older children. This will assist clinicians to appropriately assess for the presence of myocardial injury in this population.

Pathophysiological pathway differences in children who present with COVID-19 ARDS compared to COVID -19 induced MIS-C

COVID-19 has infected more than 275 million worldwide (at the beginning of 2022). Children appear less susceptible to COVID-19 and present with milder symptoms. Cases of children with COVID-19 developing clinical features of Kawasaki-disease have been described. Here we utilise Mass Spectrometry proteomics to determine the plasma proteins expressed in healthy children pre-pandemic, children with multisystem inflammatory syndrome (MIS-C) and children with COVID-19 induced ARDS. Pathway analyses were performed to determine the affected pathways. 76 proteins are differentially expressed across the groups, with 85 and 52 proteins specific to MIS-C and COVID-19 ARDS, respectively. Complement and coagulation activation are implicated in these clinical phenotypes, however there was significant contribution of FcGR and BCR activation in MIS-C and scavenging of haem and retinoid metabolism in COVID-19 ARDS. We show global proteomic differences in MIS-C and COVID-ARDS, although both show complement and coagulation dysregulation. The results contribute to our understanding of MIS-C and COVID-19 ARDS in children.

While rare, SARS-CoV-2-infected children can develop severe COVID-19 (ARDS) or inflammatory syndrome (MIS-C). Here, the authors use proteomics to characterize hundreds of blood proteins and identify key biological pathways that differentiate MIS-C and ARDS.

Fibrin clot characteristics and anticoagulant response in a SARS‐CoV‐2‐infected endothelial model

Coronavirus disease 2019 (COVID‐19) patients have increased thrombosis risk. With increasing age, there is an increase in COVID‐19 severity. Additionally, adults with a history of vasculopathy have the highest thrombotic risk in COVID‐19. The mechanisms of these clinical differences in risk remain unclear. Human umbilical vein endothelial cells (HUVECs) were infected with SARS‐CoV‐2, influenza A/Singapore/6/86 (H1N1) or mock‐infected prior to incubation with plasma from healthy children, healthy adults or vasculopathic adults. Fibrin on surface of cells was observed using scanning electron microscopy, and fibrin characteristics were quantified. This experiment was repeated in the presence of bivalirudin, defibrotide, low‐molecular‐weight‐heparin (LMWH) and unfractionated heparin (UFH). Fibrin formed on SARS‐CoV‐2 infected HUVECs was densely packed and contained more fibrin compared to mock‐infected cells. Fibrin generated from child plasma was the thicker than fibrin generated in vasculopathic adult plasma (p = 0.0165). Clot formation was inhibited by LMWH (0.5 U/ml) and UFH (0.1–0.7 U/ml). We show that in the context of the SARS‐CoV‐2 infection on an endothelial culture, plasma from vasculopathic adults produces fibrin clots with thinner fibrin, indicating that the plasma coagulation system may play a role in determining the thrombotic outcome of SARS‐CoV‐2 infection. Heparinoid anticoagulants were most effective at preventing clot formation.

Establishing the reference interval for pulse oxygen saturation in neonates at high altitudes: protocol for a multicentre, open, cross-sectional study

INTRODUCTION

Establishing the reference interval for pulse oxygen saturation (SpO₂) is essential for sensitively identifying neonatal hypoxaemia due to various causes. However, the reference interval for high altitudes has not yet been established, and existing studies have many limitations. This study will aim to establish the reference interval for various high altitudes and determine whether preductal and postductal measurements at the same altitude vary.

METHODS AND ANALYSIS

This is a multicentre, open, cross-sectional study, which will begin in February 2022. Approximately 2000 healthy full-term singleton neonates will be recruited from six hospitals (altitude ≥2000 m) in Qinghai Province, China. The participating hospitals will use a uniform pulse oximeter type. The measurements will be performed between 24 hours after birth and discharge. During the measurement, the neonate will be awake and quiet. Preductal and postductal measurements will be performed. The measurement time, site and results will be recorded and input, along with the collected basic information, into the perinatal cloud database. We will carry out strict quality control for basic information collection, measurement and data filing. We will perform descriptive statistics on the distribution range of the collected data, determine the lower limit value of the reference interval for each hospital and the corresponding altitude, perform curve fitting for the lower limit value, use the altitude as a covariate for the function corresponding to the fitted curve, establish the prediction equation and ultimately determine the reference intervals of each high altitude location.

ETHICS AND DISSEMINATION

Our protocol has been approved by the Medical Ethics Committee of all participating hospitals. We will publish our study results in academic conferences and peer-reviewed public journals.

TRIAL REGISTRATION NUMBER

NCT05115721.

Indirectly determined hematology reference intervals for pediatric patients in Berlin and Brandenburg

OBJECTIVES

Establishing direct reference intervals (RIs) for pediatric patients is a very challenging endeavor. Indirectly determined RIs can address this problem by utilization of existing clinical laboratory databases. In order to provide better laboratory services to the local pediatric population, we established population-specific hematology RIs via data mining.

METHODS

Our laboratory information system (LIS) was searched for pediatric blood counts of patients aged from 0 days to 18 years, performed from 1st of January 2018 until 31st of March 2021. In total, 27,554 blood counts on our SYSMEX XN-9000 were initially identified. After application of pre-defined exclusion criteria, 18,531 sample sets remained. Age- and sex-specific RIs were established in accordance with International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) and Clinical & Laboratory Standards Institute (CLSI) recommendations.

RESULTS

When compared to pediatric RIs supplied by other authors, the RIs determined specifically for pediatric patients from Berlin and Brandenburg showed several relevant differences, especially with regard to white blood cell counts (WBCs), red blood cell counts (RBCs), red cell distribution widths (RDW) and platelet counts (PLTs) within the distinct age groups. Additionally, alterations to several published age-specific partitions had to be made, while new sex-specific partitions were introduced for WBCs and PLTs.

CONCLUSIONS

Generic RIs from textbooks, manufacturer information and medical publications - even from nationwide or multicenter studies - commonly used in many laboratories might not reflect the specifics of local patient populations properly. RIs should be tailored to the serviced patient population whenever possible. Careful data mining appears to be suitable for this task.

The proportion of low and intermediate molecular weight von Willebrand Factor multimers are different in neonates and infants compared to adults

N/A.

Interindividual Biological Variability of Reticulocytes and Their Maturation Fractions in the Pediatric Population

OBJECTIVES

Because published data about the variability of reticulocyte counts in children are scarce, the interindividual biological variability of the automated reticulocyte count and its maturation fractions according to age and sex were analyzed.

METHODS

A retrospective, observational, analytical study was designed to establish and compare normal values of the automated reticulocyte count and its maturation fractions in different age and sex groups. The sample was drawn from results of CBC counts performed in children aged between 2 months and 18 years using an indirect sampling methodology.

RESULTS

A total of 9,362 CBC counts were analyzed. Automated reticulocyte count decreased between 2 months and 3 years of age and slowly increased thereafter, showing higher values in girls up to the age of 9 years, and equalized by sex thereafter. Immature reticulocyte fraction increased until 7 months of age; decreased progressively until 4 years of age; and then showed a discreet but constant rise, with significantly higher values in boys older than 1 year. The low-fluorescence fraction was relatively steady, with significantly higher values in girls aged 8 months and older.

CONCLUSIONS

The automated reticulocyte count and its maturation fractions show significant variations related to age and sex in pediatric patients.

Establishing paediatric reference intervals for thyroid function tests in Croatian population on the Abbott Architect i2000

Introduction

Evaluation of thyroid function is often requested and therefore defining paediatric reference intervals (RIs) is of vital importance. Currently, there is a distinct lack of paediatric RIs for thyroid function tests in Croatia. Thus, we established RIs for thyroid stimulating hormone (TSH), total triiodothyronine (TT3), total thyroxine (TT4), free triiodothyronine (FT3) and free thyroxine (FT4) in the Croatian paediatric population.

Materials and methods

Reference intervals were calculated from 397 apparently healthy children, aged from 2 days to < 19 years. Serum samples were analysed for thyroid function tests on the Abbott Architect i2000. Age- and sex-specific 95% RIs with 90% confidence intervals were established according to Clinical and Laboratory Standards Institute guidelines. To express the magnitude of sex and age variation, standard deviation ratio (SDR) was calculated using two-level nested ANOVA. The criterion for considering partitioning reference values was set to SDR > 0.3.

Results

All thyroid function tests required age partitioning, confirmed by SDR above 0.3. There was no need for sex partitioning, confirmed by SDR below 0.3. Still, FT3 was partitioned due to visually noticeable sex related difference for the oldest group (12 years to < 19 years).

Conclusion

This is the first study to establish RIs for thyroid function tests in the Croatian paediatric population. We propose RIs for widely used Abbott platform, thus giving laboratories method- and population-specific paediatric RIs for thyroid function tests that should improve clinical test interpretation.

Indirect determination of serum creatinine reference intervals in a Pakistani pediatric population using big data analytics

BACKGROUND

The indirect methods of reference intervals (RI) establishment based on data mining are utilized to overcome the ethical, practical challenges and the cost associated with the conventional direct approach.

AIM

To generate RIs for serum creatinine in children and adolescents using an indirect statistical tool.

METHODS

Data mining of the laboratory information system was performed for serum creatinine analyzed from birth to 17 years for both genders. The timeline was set at six years from January 2013 to December 2018. Microsoft Excel 2010 and an indirect algorithm developed by the German Society of Clinical Chemistry and Laboratory Medicine’s Working Group on Guide Limits were used for the data analysis.

RESULTS

Data were extracted from 96104 samples and after excluding multiple samples for the same individual, we calculated RIs for 21920 males and 14846 females, with stratification into six discrete age groups.

CONCLUSION

Serum creatinine dynamics varied significantly across gender and age groups.

Pediatric reference interval verification for endocrine and fertility hormone assays on the Abbott Alinity system

OBJECTIVES

The Canadian Laboratory Initiative on Pediatric Reference Intervals (CALIPER) has developed an extensive database of reference intervals (RIs) for several biomarkers on various analytical systems. In this study, pediatric RIs were verified for key immunoassays on the Abbott Alinity system based on the analysis of healthy children samples and comparison to comprehensive RIs previously established for Abbott ARCHITECT assays.

METHODS

Analytical performance of Alinity immunoassays was first assessed. Subsequently, 100 serum samples from healthy children recruited with informed consent were analyzed for 16 Alinity immunoassays. The percentage of test results falling within published CALIPER ARCHITECT reference and confidence limits was determined. If ≥ 90% of test results fell within the confidence limits, they were considered verified based on CLSI guidelines. If <90% of test results fell within the confidence limits, additional samples were analyzed and new Alinity RIs were established.

RESULTS

Of the 16 immunoassays assessed, 13 met the criteria for verification with test results from ≥ 90% of healthy serum samples falling within the published ARCHITECT confidence limits. New CALIPER RIs were established for free thyroxine and prolactin on the Alinity system. Estradiol required special considerations in early life.

CONCLUSIONS

Our data demonstrate excellent concordance between ARCHITECT and Alinity immunoassays, as well as the robustness of previously established CALIPER RIs for most immunoassays, eliminating the need for de novo RI studies for most parameters. Availability of pediatric RIs for immunoassays on the Alinity system will assist clinical laboratories using this new platform and contribute to improved clinical decision-making.

POCT: An Inherently Ideal Tool in Pediatric Laboratory Medicine

Point of care testing (POCT) is important in the provision of timely laboratory test results and continues to gain specific appreciation in the setting of pediatric healthcare. POCT platforms offer several advantages compared to central laboratory testing, including improved clinical outcomes, reduced time to diagnosis, length of stay, and blood volume requirements, as well as increased accessibility. These advantages are most pronounced in acute care settings such as pediatric emergency departments, intensive care units, and in remote settings, wherein rapid patient assessment and prognostication is essential to patient outcomes. The current review provides an overview and critical discussion of the evidence supporting clinical implementation of POCT systems in pediatric clinical decision-making, including but not limited to the diagnosis of viral and bacterial infection, identification of critical glucose and electrolyte dysregulation, and prognostication of post-operative inpatients. Important considerations for test result reporting and interpretation are also discussed, including analytical concordance between POCT systems and central laboratory analyzers as well as availability of pediatric reference intervals for key analytes on POCT systems. Notably, a paucity of evidence-based pediatric reference intervals for test interpretation for critical care parameters on POCT platforms is highlighted, warranting further study and unique consideration prior to clinical implementation.

Pediatric reference intervals for endocrine markers and fertility hormones in healthy children and adolescents on the Siemens Healthineers Atellica immunoassay system

OBJECTIVES

Rapid development in childhood and adolescence combined with lack of immunoassay standardization necessitates the establishment of age-, sex-, and assay-specific reference intervals for immunochemical markers. This study established reference intervals for 11 immunoassays on the new Siemens Healthineers Atellica® IM Analyzer in the healthy CALIPER cohort.

METHODS

A total of 600 healthy participants (birth to 18 years) were recruited from the community, and serum samples were collected with informed consent. After sample analysis, age- and sex-specific differences were assessed, and outliers were removed. Reference intervals were established using the robust method (40-<120 participants) or nonparametric method (≥120 participants).

RESULTS

Of the 11 immunoassays studied, nine required age partitioning (i.e., dehydroepiandrosterone-sulfate, estradiol, ferritin, folate, follicle-stimulating hormone, luteinizing hormone, progesterone, testosterone, vitamin B12), and seven required sex partitioning. Free thyroxine and thyroid-stimulating hormone demonstrated no significant age- and/or sex-specific differences.

CONCLUSIONS

Overall, the age- and sex-specific trends observed closely mirrored those previously reported by CALIPER on other platforms as well as other internationally recognized studies. However, established lower and upper limits demonstrated some discrepancies between published values from healthy cohorts on alternate analytical systems, highlighting differences between manufacturers and the need for platform-specific reference intervals for informed pediatric clinical decision-making.

Investigating potential protein markers of cardiovascular disease in children with type 1 diabetes mellitus

BACKGROUND

Type 1 diabetes mellitus (T1DM) is a metabolic disease characterized by dysglycaemia. Cardiovascular disease (CVD) is a major complication among T1DM patients and the leading cause of mortality later in life.

METHODS

The study subjects consisted of T1DM children with poor glycemic control (HbA1c > 7.5%) and healthy age and gender matched controls. Venous blood samples were collected and tested by utilizing a novel immunoassay panel with 96 protein biomarkers. Data were analyzed using non-linear regression analysis and the expression of biomarkers was compared between T1DM and healthy control groups using an unpaired student's t-test. Dynamic principal component analysis (PCA) was operated based on the differentially expressed proteins.

RESULTS

Ten T1DM children and 10 healthy controls were analyzed. Twelve CVD markers show significant differential expression between T1DM patients and healthy controls (p < 0.05). Dynamic PCA clustering based on differentially expressed proteins demonstrated an obvious clustering between the two populations.

CONCLUSIONS

This preliminary study reveals the feasibility of utilizing a novel immunoassay panel to investigate potential biomarkers for predicting incipient CVD in children with T1DM. In future, longitudinal studies are required to track the relationships between measurements of the selected protein markers and the development of CVD in T1DM patients.

Continuous reference intervals for leukocyte telomere length in children: the method matters

OBJECTIVES

Children with very short telomeres commonly develop bone marrow failure and other severe diseases. Identifying the individuals with short telomeres can improve outcome of bone marrow transplantation, with accurate diagnosis requiring the use of age-matched reference intervals (RIs). This study aimed to establish RIs for telomere length (TL) in children using three commonly used methods for TL measurement.

METHODS

Healthy children aged 30 days to 18 years were recruited for assessment using age as a continuous variable. Venous blood samples were collected and leukocyte TL was measured using terminal restriction fragment (TRF) analysis, quantitative PCR (QPCR) and flow cytometry with fluorescence in situ hybridization (Flow-FISH). Fractional polynomial model and quantile regression were performed to generate continuous RIs. Factors that might contribute to variation in TL, such as gender, were also examined.

RESULTS

A total of 212 samples were analyzed. Continuous RIs are presented as functions of age. TRF analysis and QPCR showed significant negative correlation between TL and age (r=-0.28 and r=-0.38, p<0.001). In contrast, Flow-FISH showed no change in TL with age (r=-0.08, p=0.23). Gender did not have significant influence on TL in children.

CONCLUSIONS

This study provides three options to assess TL in children by establishing method-specific continuous RIs. Choosing which method to use will depend on several factors such as amount and type of sample available and required sensitivity to age-related change.

High-resolution pediatric reference intervals for 15 biochemical analytes described using fractional polynomials

OBJECTIVES

Assessment of children's laboratory test results requires consideration of the extensive changes that occur during physiological development and result in pronounced sex- and age-specific dynamics in many biochemical analytes. Pediatric reference intervals have to account for these dynamics, but ethical and practical challenges limit the availability of appropriate pediatric reference intervals that cover children from birth to adulthood. We have therefore initiated the multi-center data-driven PEDREF project (Next-Generation Pediatric Reference Intervals) to create pediatric reference intervals using data from laboratory information systems.

METHODS

We analyzed laboratory test results from 638,683 patients (217,883-982,548 samples per analyte, a median of 603,745 test results per analyte, and 10,298,067 test results in total) performed during patient care in 13 German centers. Test results from children with repeat measurements were discarded, and we estimated the distribution of physiological test results using a validated statistical approach (kosmic).

RESULTS

We report continuous pediatric reference intervals and percentile charts for alanine transaminase, aspartate transaminase, lactate dehydrogenase, alkaline phosphatase, γ-glutamyl-transferase, total protein, albumin, creatinine, urea, sodium, potassium, calcium, chloride, anorganic phosphate, and magnesium. Reference intervals are provided as tables and fractional polynomial functions (i.e., mathematical equations) that can be integrated into laboratory information systems. Additionally, Z-scores and percentiles enable the normalization of test results by age and sex to facilitate their interpretation across age groups.

CONCLUSIONS

The provided reference intervals and percentile charts enable precise assessment of laboratory test results in children from birth to adulthood. Our findings highlight the pronounced dynamics in many biochemical analytes in neonates, which require particular consideration in reference intervals to support clinical decision making most effectively.

Pediatric Thromboelastograph 6s and Laboratory Coagulation Reference Values

CONTEXT.—

Specific reference intervals (RIs) facilitate accurate interpretation of results. Coagulation assay results may vary by demographics and also between reagents and analyzers used. Current Thromboelastograph 6s (TEG 6s) Hemostasis Analyzer RIs were generated from adult samples.

OBJECTIVE.—

To generate reagent analyzer-specific pediatric RIs for TEG 6s and coagulation parameters.

DESIGN.—

A prospective, observational, single-center study of healthy children undergoing general anesthesia (January 3, 2017 to January 3, 2019). Venous blood samples were obtained for TEG 6s (Kaolin, Kaolin-Heparinase, Rapid and Functional Fibrinogen assays) and coagulation parameters (activated partial thromboplastin time, prothrombin time, thrombin clotting time, Echis time, antithrombin activity, and fibrinogen concentration using Instrumentation Laboratory ACL-TOP analyzers). Differences between activated partial thromboplastin time and prothrombin time reagents were investigated using mixed-effects regression, comparing maximum coefficients-of-variation with assay-specific allowable variation. RIs (lower/upper limits 2.5th of 97.5th percentiles) were generated using the following 2 methods: within discrete age-groups (neonates [<1 month], infants [1 month-1 year], young children [1-5 years], older children [6-10 years], and adolescents [11-16 years]), and modeled as functions of age and/or sex using quantile regression, including significant fractional polynomial and interaction terms.

RESULTS.—

Variation between prothrombin time and activated partial thromboplastin time assays using different reagents was clinically significant. Reagent-analyzer specific pediatric RIs were generated using data from 254 children. Discrete and model-based RIs varied by age for all coagulation parameters and TEG 6s variables in all assays.

CONCLUSIONS.—

We report reagent-analyzer specific pediatric RIs for TEG 6s and coagulation parameters. Observed variation reinforces recommendations for laboratory-specific RIs. These findings improve accuracy of interpretation of clinical results, provide a foundation for comparison and validation of tests in pathology and illustrate feasibility and advantages of model-based RI approaches.

Clinical thresholds for diagnosing iron deficiency: comparison of functional assessment of serum ferritin to population based centiles

Low serum ferritin is diagnostic of iron deficiency, yet its published lower cut-off values are highly variable, particularly for pediatric populations. Lower cut-off values are commonly reported as 2.5th percentiles, and is based on the variation of ferritin values in the population. Our objective was to determine whether a functional approach based on iron deficient erythropoiesis could provide a better alternative. Utilizing 64,443 ferritin test results from pediatric electronic health records, we conducted various statistical techniques to derive 2.5th percentiles, and also derived functional reference limits through the association between ferritin and erythrocyte parameters: hemoglobin, mean corpuscular volume, mean cell hemoglobin concentration, and red cell distribution width. We find that lower limits of reference intervals derived as centiles are too low for clinical interpretation. Functional limits indicate iron deficiency anemia starts to occur when ferritin levels reach 10 µg/L, and are largely similar between genders and age groups. In comparison, centiles (2.5%) presented with lower limits overall, with varying levels depending on age and gender. Functionally-derived limits better reflects the underlying physiology of a patient, and may provide a basis for deriving a threshold related to treatment of iron deficiency and any other biomarker with functional outcomes.

Reference intervals for serum cystatin C in neonates and children 30 days to 18 years old

BACKGROUND

Serum cystatin C (CysC) is a promising biomarker of kidney function, which has higher accuracy and sensitivity when compared with creatinine. To better utilize serum CysC in clinical practice, this study aimed to establish continuous paediatric reference intervals (RIs) for serum CysC.

METHODS

The study subjects consisted of healthy term neonates and children aged 30 days to 18 years. Venous blood samples were collected and serum CysC levels were measured using the immunoturbidimetric measurement principle. Fractional polynomial regression model and quantile regression was applied in the statistical analysis to generate continuous RIs.

RESULTS

A total of 378 samples with equal numbers of males and females were analysed for serum CysC. No outliers were found in this analysis. The continuous RIs are presented as equations and graphical scatterplots.

CONCLUSIONS

This study established continuous paediatric reference intervals (RIs) for serum CysC in healthy term neonates and children. The continuous RIs generated from this study show age-based dynamic changes as well as blood group and gender-specific differences for serum CysC. Graphical abstract.

Gender and age-specific reference intervals of common biochemical analytes in Chinese population: Derivation using real laboratory data

Background

Indirect sampling methods are not only inexpensive but also efficient for establishing reference intervals (RIs) using clinical data. This study was conducted to select fully normal records to establish ageand gender-specific RIs for common biochemical analytes by laboratory data mining.

Methods

In total, 280,206 records from 2014 to 2018 were obtained from Peking Union Medical College Hospital. Common biochemical analytes total protein, albumin, total bilirubin (TBil), direct bilirubin (DBil), alanine aminotransferase (ALT), glutamyltranspeptidase (GGT), alkaline phosphatase (ALP), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), potassium, sodium, chlorine, calcium, urea, glucose, uric acid (UA), inorganic phosphorus, creatinine (Cr), total cholesterol, triglyceride, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol] were measured using an automatic analyzer. Sources of variation were identified by multiple regression analysis. The 2.5th and 97.5th percentiles were calculated as the lower and upper limits of the RIs, respectively.

Results

Gender was the major source of variation among the 13 common biochemical analytes with an rp > 0.15. In contrast to the value listed in the WS/T 404, nearly all RIs established in this study were significantly narrower. Furthermore, age-specific RIs should be determined for DBil, LDH, and urea, whereas gender-specific RIs are suggested for GGT, LDH, and urea.

Conclusions

We recommend that gender-specific RIs should be established for ALT, AST, GGT, DBil, TBil, UA, and Cr as well as genderand age-specific RIs for urea and ALP. Through indirect sampling, ageand gender-specific RIs for common biochemical analytes were established and analyzed.

Validation of the HAPPI Kids Continuous Age-Specific Pediatric Reference Intervals

Introduction

To facilitate best possible patient care, reference intervals (RIs) adopted by a laboratory must be appropriate for the population demographics and, where applicable, the analytical principle and/or the analytical instrument used. While guidelines from the Clinical and Laboratory Standard Institute (CLSI) recommend a validation process for discrete RIs, there are no current recommendations for the validation process for continuous RIs. This study aimed to validate recently published, HAPPI Kids continuous RIs, in a routine laboratory.

Methods

Initially, the difference in test results between the primary study laboratory that contributed to previous RIs development and a routine laboratory was assessed using specimens from 77 children tested in both laboratories using the Siemens ADVIA 1800 or Centaur/XP/XPT. Later, validation of the HAPPI Kids RIs was undertaken using 279 pediatric samples tested on the same analyzer type in the routine laboratory. The previously published RIs were validated if more than 90% of results in the routine laboratory were within the RIs.

Results

There was minimal evidence of clinically significant differences in test results between the primary and routine laboratories. The continuous RIs were validated after initial analysis for 16 of the 18 biochemistry analytes tested, and after secondary analysis for the remaining 2 analytes.

Conclusion

This study validates the HAPPI Kids RIs in a routine laboratory, satisfying the laboratory accreditation requirements for evaluation, implementation, and sourcing of RIs. In addition, this study presents a modification of the current CLSI method for validation of continuous RIs that will benefit routine laboratories in general.

Paediatric Reference Intervals: Current Status, Gaps, Challenges and Future Considerations

Establishing paediatric reference intervals (RIs) is a challenging task due to difficulties in subject recruitment, collection of adequate blood volume, and the inherent physiological changes of many biomarkers with age. Despite these challenges, several national and international initiatives have demonstrated: (a) the feasibility of prospectively designed paediatric RI studies; (b) the development of continuous RIs; and (c) the comparison of reference values across analyser types to harmonise paediatric RIs. Whilst these studies have improved the interpretation of paediatric test results and compliance with international accreditation (ISO15189) requirements, several gaps and challenges in translating current paediatric RIs into routine laboratory practice remain. Future priorities for paediatric RI studies include: (a) determination of the impact of discrete versus continuous RIs, analyser-specific versus harmonised RIs, and prospective collection versus data mining on the proportion of results outside the RIs; (b) understanding the clinical implications of analyser-to-analyser variation in reference values and use of evidence-based paediatric harmonised RIs where applicable; (c) adaptation of laboratory information systems to incorporate continuous RIs; (d) further understanding of the biological variation in paediatric biomarkers; (e) studies to address the paucity of accurate data for neonatal RI development; (f) periodic demonstration of RIs being clinically 'fit-for purpose'; and (g) agreement and policy updates for use of modern, best practice statistical methods in estimation of paediatric RIs. Furthermore, in vitro diagnostic manufacturers may require incentivised paediatric RI studies and publications through co-ordinated grants and collaboration at end-user sites to reduce the burden on sole users.

Reference Values for 30 Common Biochemistry Analytes Across 5 Different Analyzers in Neonates and Children 30 Days to 18 Years of Age

BACKGROUND

Age-specific reference intervals (RIs) have been developed for biochemistry analytes in children. However, the ability to interpret results from multiple laboratories for 1 individual is limited. This study reports a head-to-head comparison of reference values and age-specific RIs for 30 biochemistry analytes for children across 5 analyzer types.

METHODS

Blood was collected from healthy newborns and children 30 days to &lt;18 years of age. Serum aliquots from the same individual were analyzed on 5 analyzer types. Differences in the mean reference values of the analytes by the analyzer types were investigated using mixed-effect regression analysis and by comparing maximum variation between analyzers with analyte-specific allowable total error reported in the Westgard QC database. Quantile regression was used to estimate age-specific RIs using power variables in age selected by fractional polynomial regression for the mean, with modification by sex when appropriate.

RESULTS

The variations of age-specific mean reference values between analyzer types were within allowable total error (Westgard QC) for most analytes, and common age-specific reference limits were reported as functions of age and/or sex. Analyzer-specific reference limits for all analytes on 5 analyzer types are also reported as functions of age and/or sex.

CONCLUSIONS

This study provides quantitative and qualitative measures of the extent to which results for individual children can or cannot be compared across analyzer types, and the feasibility of RI harmonization. The reported equations enable incorporation of age-specific RIs into laboratory information systems for improving evidence-based clinical decisions in children.