Drug testing in support of the diagnosis of neonatal abstinence syndrome: The current situation.

Illicit drug use during pregnancy is a concern worldwide, with many international studies describing attempted strategies to mitigate this problem. Drug misuse during pregnancy is associated with significant maternal as well as perinatal complications, which include a high incidence of stillbirths, fetal distress, neonatal abstinence syndrome (NAS) and increased neonatal mortality. Unfortunately, the identification of a drug-exposed mother or neonate is challenging. Maternal disclosure of drug use is often inaccurate, principally due to psychosocial factors including behavioral denial or the fear of the consequences resulting from such admissions. Likewise, many infants who have been exposed to drugs in utero may appear normal at birth and initially show no overt manifestations of drug effects. Thus, the identification of the drug-exposed infant requires a high index of clinical suspicion. Conversely, analytical testing is an objective means of determining drug exposure when it may be necessary to document proof of the infant's exposure to illicit drugs. The review will discuss the different matrices that are most commonly used for testing (e.g., maternal urine, neonatal urine, meconium, and umbilical cord), the strengths and limitations for each matrix, which drugs and metabolites are appropriate for testing, the various testing methods, and the advantages and disadvantages of each method.

The analytical performance of six urine drug screens on cobas 6000 and ARCHITECT i2000 compared to LC-MS/MS gold standard.

BACKGROUND: Immunoassays provide a rapid tool for the screening of drugs-of-abuse (DOA). However, results are presumptive and confirmatory testing is warranted. To reduce associated cost and delay, laboratories should employ assays with high positive and negative predictive values (PPVs and NPVs). Here, we compared the results of urine drug screens on cobas 6000 (cobas) and ARCHITECTi2000 (ARCHITECT) platforms for six drugs against LC-MS/MS to assess the analytical performance of these assays. METHODS: Eighty nine residual urine specimens, which tested positive for amphetamine, THC-COOH, benzoylecgonine, EDDP, opiates and/or oxycodone during routine drug testing, were stored frozen until later confirmation by LC-MS/MS. Immunoassays were performed on cobas and ARCHITECT using a split sample. A third aliquot from these samples was tested by LC-MS/MS to assess the percentage of false positive, false negative, true positive and true negative results and calculate the PPVs and NPVs for each immunoassay. RESULTS: The PPVs of THC-COOH and EDDP assays were 100% on both platforms. Suboptimal PPVs were achieved for oxycodone (cobas, 57.1% vs ARCHITECT, 66.7%), amphetamine (77.8 vs. 100%), opiates (80.0 vs. 84.6%) and benzoylecgonine (88.9 vs. 84.2%) assays. The NPV was 100% for cobas and ARCHITECT oxycodone assays. Lower NPVs were achieved for THC-COOH (cobas, 28.6% vs ARCHITECT, 25.0%), EDDP (72.7% for both assays), benzoylecgonine (74.4% vs 73.8%), amphetamine (83.3% vs 82.8%) and opiates (100% vs 85.3%). CONCLUSION: Overall, cobas and ARCHITECT urine drug screens have comparable analytical performance. Confirmatory testing is warranted for positive test results especially for oxycodone, amphetamine, opiates and cocaine. Negative drug screen results must be interpreted with caution especially for THC-COOH, EDDP, benzoylecgonine, amphetamine and opiates.

Effective interventions to improve the quality of critically high point-of-care glucose meter results.

OBJECTIVES: Point-of-care testing (POCT) is testing performed outside the traditional laboratory, often at the patient bedside. In hospital settings, blood glucose is the most common POCT. Staff performing POCT are not usually laboratory trained; they are clinical staff with a primary focus on treating patients. Clinical staff find POCT quality assurance (QA) practices burdensome and are often non-compliant. In hospitals within EORLA (Eastern Ontario Regional Laboratories Association), all critically high POCT glucose results must be repeated prior to acting, according to policy. Compliance with this policy is audited regularly. DESIGN: and methods: All POCT glucose tests performed in participating sites between January and June 2018 and June and December 2019 were audited for compliance with the critical repeat policy. The discordant repeat rate was also determined for each audit period. Between January and May 2019, there were interventions aimed at improving compliance with the repeat policy. RESULTS: Compliance with the critical repeat policy increased from 30 to 57% in 2019 compared to 2018, following nursing education and implementation of notifications on the glucose meters themselves. The rate of discordant repeat results (>20% different from initial) also improved at most sites in 2019 compared to 2018. Nurses cited insufficient cleaning of patient hands prior to initial testing as the primary reason for discordant repeats. CONCLUSIONS: Operator compliance with POCT QA policies is an ongoing challenge requiring continual audit, feedback and education. A strong POCT multi-disciplinary committee with supports from senior and clinical leadership in an organization are key to improving compliance.

Clinical decisions following implementation of asparaginase activity monitoring in pediatric patients with acute lymphoblastic leukemia: Experience from a single-center study.

We undertook this retrospective study to describe decisions made following asparaginase activity monitoring implementation at our center. Clinically apparent reactions (CARs) and asparaginase activity monitoring costs were described. Patients with acute lymphoblastic leukemia, aged <18 years who received asparaginase between April 2016 and September 2017, were included. Decisions made following receipt of asparaginase activity results were categorized as continuation, modification, premedication, or discontinuation. We included 129 patients (median age: 5.33 years) receiving 565 asparaginase doses. CARs were observed following 25 asparaginase doses (19/361 [5.3%] pegaspargase). A total of 224 asparaginase activity levels were ordered in 88 patients. Following receipt of 190 asparaginase activity results, asparaginase therapy was continued, modified, or premedicated in 188 (98.9%), 1 (0.005%), and 1 (0.005%) cases, respectively. Inadequate asparaginase activity was observed in three patients receiving Erwinia asparaginase. Asparaginase activity monitoring allowed patients with pegaspargase-associated CAR and adequate activity to continue therapy unchanged and was cost neutral.

Predicting Escitalopram Exposure to Breastfeeding Infants: Integrating Analytical and In Silico Techniques.

BACKGROUND: Escitalopram is used for post-partum depression; however, there are limited pharmacokinetic data of escitalopram in milk and plasma of infants breastfed by women taking the drug. OBJECTIVE: The objective of this study was to apply physiologically-based pharmacokinetic (PBPK) modelling to predict infant drug exposure (plasma area under the curve from time zero to infinity [AUC∞]) based on drug monitoring data of escitalopram in breast milk. METHODS: Using a newly developed liquid chromatography-tandem mass spectrometry (LC-MS/MS) method, we quantified escitalopram concentrations in milk samples of 18 breastfeeding women with escitalopram therapy at steady state, collected at three to five time points. The escitalopram concentrations in breast milk were used with infant feeding parameters from the literature to simulate infant daily dose. We used PK-Sim® to develop an adult PBPK model for escitalopram and extrapolated it to a population of 1600 infants up to 12 months of age. An integration of the simulated infant daily dose and the virtual infants with variable physiological-pharmacological parameters was used to predict drug exposure (plasma AUC∞) distribution in the population of infants breastfed by women receiving escitalopram 20 mg/day. RESULTS: Escitalopram concentrations in milk were 50 ± 17 ng/mL (mean ± standard deviation). The simulated infant plasma AUC∞ following escitalopram exposure through breast milk was low, with a median of 1.7% (range 0.5-5.9%) of the corresponding maternal plasma AUC∞, indicating no substantial exposure. CONCLUSIONS: Infant exposure levels to escitalopram in breast milk are low. A PBPK modeling approach can be used to translate data on drug monitoring in milk into a population distribution of infant plasma levels for drug safety assessment.

Evaluation of electrochemiluminescence immunoassays for immunosuppressive drugs on the Roche cobas e411 analyzer.

Background:  Therapeutic drug monitoring of immunosuppressant drugs are used to monitor drug efficacy and toxicity and to prevent organ transplant rejection. This study evaluates the analytical performance of semi-automated electrochemiluminescence immunoassays (ECLIA) for cyclosporine (CSA), tacrolimus (TAC) and sirolimus (SRL) on the Roche cobas e 411 analyzer at a major transplant hospital to assess method suitability and limitations. Methods: Residual whole blood samples from patients undergoing immunosuppressant therapy were used for evaluation. Imprecision, linearity, functional sensitivity, method comparisons and lot-to-lot comparisons were assessed. Results: Total imprecision ranged from 3.3 to 7.1% for CSA, 3.9 to 9.4% for TAC, and 4.6 to 8.2% for SRL. Linearity was verified from 30.0 to 960.9 µg/L for CSA, from 1.1 to 27.1 µg/L for TAC, and from 0.5 to 32.3 µg/L for SRL. The functional sensitivity met the manufacturer's claims and was determined to be <6.5 µg/L for CSA, 1.1 µg/L for TAC, and <0.1 µg/L for SRL (CV≤20%). Deming regression analysis of method comparisons with the ARCHITECT immunoassay yielded slopes of 0.917 (95%CI: 0.885-0.949) and r of 0.985 for CSA, 0.938 (95%CI: 0.895-0.981) and r of 0.974 for TAC, and 0.842 (0.810-1.110) and r of 0.982 for SRL. Deming regression analysis of comparisons with the LC-MS/MS method yielded slopes of 1.331 (95%CI: 1.167-1.496) and r of 0.969 for CSA, 0.924 (95%CI: 0.843-1.005) and r of 0.984 for TAC, and 0.971 (95%CI: 0.913-1.030) and r of 0.993 for SRL. Conclusions: The cobas e 411 ECLIA for CSA, TAC, and SRL have acceptable precision, linearity, and functional sensitivity. The method comparisons correlated well with the ARCHITECT immunoassay and LC-MS/MS and is fit for therapeutic drug monitoring.

Reference intervals for growth arrest-specific 6 protein in adults.

The objective of this study was to establish reference intervals for growth arrest-specific 6 (GAS6), a vitamin K-dependent protein, in human adult plasma according to the Guideline of Clinical and Laboratory Standards Institute (CLSI) C28-A3. Blood samples were collected from 308 healthy volunteers aged 18-72 (157 female, 151 male). A non-parametric approach was used to calculate the reference interval. The plasma GAS6 reference interval was determined, with 90% confidence interval: the lower limit (2.5 percentile) was 2.5 (1.9-3.1) µg/L and the upper limit (97.5 percentile) = 18.8 (18.0-22.3) µg/L. Harris-Boyd's test did not suggest partitioning by age or gender: medians for males [7.8 (5.8-10.7) µg/L] and females [9.9 (7.1-13.5) µg/L]. Three age-subgroups were tested: 18-29 years (n = 168); 30-44 years (n = 73); 45-72 years (n = 67). The intra- and inter-assay variations were 12.6% (mean, 5.2 ± 0.7 µg/L) and 14.0% (mean, 9.2 ± 1.3 µg/L), respectively. The mean recovery was 104%. This study reports plasma GAS6 reference intervals established first according to the guideline of CLSI C28-A3.

Nevirapine Pharmacokinetics and Safety in Neonates Receiving Combination Antiretroviral Therapy for Prevention of Vertical HIV Transmission.

BACKGROUND: Nevirapine (NVP)-based combination antiretroviral therapy is routinely prescribed to infants deemed at high risk of vertical HIV infection in our centers. We evaluated NVP pharmacokinetics and safety of this regimen. METHODS: Neonates were recruited prospectively between September 2012 and April 2015 or enrolled retrospectively if treated similarly before prospective study initiation. NVP was dosed at 150 mg/m daily for 14 days, then twice daily for 14 days. NVP levels were drawn at weeks 1, 2, and 4 [target trough (NVP-T): 3-8 mg/L]. RESULTS: Thirty-three neonates were included (23 prospectively). Median gestational age (GA) and birth weight were 38 weeks (32-41 weeks) and 2.9 kg (1.5-4.2 kg), respectively. Median NVP-Ts were 8.2 mg/L (1.6-25.1 mg/L), 3.5 mg/L (1.6-6.8 mg/L), and 4.3 mg/L (0.1-19.9 mg/L) at weeks 1, 2, and 4, respectively. The proportions with therapeutic NVP-T were 42%, 61%, and 73% at these same timepoints. Median apparent oral clearance (CL/F) increased from 0.05 L·kg·h (0.01-0.50 L·kg·h) at week 2 to 0.18 L·kg·h (0.01-0.78 L·kg·h) at week 4. Increased drug exposure [area under the curve (AUCτ)] correlated with younger GA (r = 0.459, P = 0.032) and lower birth weight (r = 0.542, P = 0.009). The most common adverse events potentially attributable to combination antiretroviral therapy were transient asymptomatic hyperlactatemia (26%), anemia (24.7%), and neutropenia (22.1%). CONCLUSIONS: Treatment dose NVP was generally well-tolerated and associated with normalization of trough levels over time in most cases without dose adjustment. Lower empiric dosing is recommended for infants <34 weeks of GA. Routine therapeutic drug monitoring may not be required for infants ≥34 weeks of GA.

Milrinone therapeutic drug monitoring in a pediatric population: Development and validation of a quantitative liquid chromatography-tandem mass spectrometry method.

BACKGROUND: Milrinone is a potent selective phosphodiesterase type III inhibitor which stimulates myocardial function and improves myocardial relaxation. Although therapeutic monitoring is crucial to maintain therapeutic outcome, little data is available. A proof-of-principle study has been initiated in our institution to evaluate the clinical impact of optimizing milrinone dosing through therapeutic drug monitoring (TDM) in children following cardiac surgery. We developed a robust LC-MS/MS method to quantify milrinone in serum from pediatric patients in real-time. METHODS: A liquid-liquid extraction procedure was used to prepare samples for analysis prior to measurement by LC-MS/MS. Performance characteristics, such as linearity, limit of quantitation (LOQ) and precision, were assessed. Patient samples were acquired post-surgery and analyzed to determine the concentration-time profile of the drug as well as to track turn-around-times. RESULTS: Within day precision was <8.3% across 3 levels of QC. Between-day precision was <12%. The method was linear from 50 to 800µg/l; the lower limit of quantification was 22µg/l. Comparison with another LC-MS/MS method showed good agreement. Using this simplified method, turnaround times within 3-6h were achievable, and patient drug profiles demonstrated that some milrinone levels were either sub-therapeutic or in the toxic range, highlighting the importance for milrinone TDM. CONCLUSIONS: This simplified and quick method proved to be analytically robust and able to provide therapeutic monitoring of milrinone in real-time in patients post-cardiac surgery.

Suitability of Becton Dickinson Vacutainer rapid serum tube for collecting and storing blood samples for antibiotic and anticonvulsant drug monitoring.

AIMS: To investigate the suitability of newly developed Becton Dickinson Vacutainer rapid serum tube (RST) for therapeutic drug monitoring of antibiotics and anticonvulsants. METHODS: Two pools of citrated whole blood were created by spiking high and low concentrations of gentamicin, vancomycin, phenytoin, lamotrigine and carbamazepine. After recalcification with 15 mmol/L calcium chloride, spiked whole blood was added into four different Becton Dickinson blood collection tubes: RST, serum separator tube, red top tube and polyethylene plain tube. Serum aliquots were collected at baseline (0 h), 2 h, 24 h, day 3 and day 7. Drug concentrations were measured in batch by HPLC and the Architect c8000. RESULTS: Gentamicin and vancomycin concentrations were stable up to 7 days in all 4 blood collection tubes. Anticonvulsants results for the RST were stable and did not deviate substantially from those of the red top and plain tubes, and demonstrated better performance than the serum separator tubes that showed significant (≥10% bias, p<0.05) decrease in phenytoin and carbamazepine levels after 3 days of storage. CONCLUSIONS: The RST provides acceptable drug stability over the course of 7 days for gentamicin, vancomycin, phenytoin and lamotrigine and over 3 days for carbamazepine.

Bupropion and Escitalopram During Lactation.

OBJECTIVE: To report a case of seizure-like symptoms in an infant exposed to bupropion and escitalopram through breastfeeding. CASE SUMMARY: A 6.5-month-old female infant, breastfed by a mother treated with bupropion XL 150 mg/d and escitalopram 10 mg/d for depression, presented to our hospital with severe emesis and tonic seizure-like symptoms. The symptoms resolved with supportive therapy. Urine toxicology screen in the infant revealed bupropion and escitalopram. Bupropion, and its active metabolite, hydroxybupropion, were analyzed and quantified both in the infant's serum and in the breast milk. Diagnostic workup for seizure etiologies was otherwise negative. After being asymptomatic for 48 hours, her discharge diagnosis was adverse events associated with bupropion and escitalopram in lactation. An objective causality assessment (Naranjo assessment) revealed that this adverse effect was probable. DISCUSSION: The adverse events in our case were associated with serum concentrations of bupropion and hydroxybupropion that are lower than the reported therapeutic range, perhaps suggesting that infants, compared with adults, may have a higher susceptibility to the epileptogenic effects of bupropion and/or hydroxybupropion. Furthermore, although we do not have escitalopram serum concentrations, this drug interaction may have had a contributing role in this case, possibly because of cytochrome P4502D6 inhibition by bupropion and metabolites. CONCLUSION: As the number of reproductive-aged women requiring polytherapy to control their depression is increasing, further research is needed to establish the safety of combined antidepressants, such as selective serotonin reuptake inhibitors and bupropion, during lactation.

Implications of serum creatinine measurements on GFR estimation and vancomycin dosing in children.

BACKGROUND: Different serum creatinine (sCr) assays may obtain different values in the same patient, causing discrepancies in estimated glomerular filtration rate (eGFR) and sCr-based vancomycin dosing calculations. OBJECTIVE: To identify potential discrepancies in sCr concentrations obtained by different assays, the compensated Jaffe (sCr-Jaffe) and the enzymatic (sCr-enz), and to compare between the eGFR and vancomycin daily dose, based on these sCr values. METHOD: sCr-Jaffe and, sCr-enz concentrations of 890 healthy children, aged 1-18 years, were available from the Canadian Laboratory Initiative in Pediatric Reference Intervals study in Ontario. For each subject, eGFR (eGFR-Jaffe, eGFR-enz) was calculated using the revised Schwartz equation, and vancomycin daily dose (Vdose-Jaffe, Vdose-enz) was calculated using a sCr-based pharmacokinetic model. RESULT: Significant, age-related differences were found in sCr concentrations, and in subsequent eGFR and Vdose, between the two assays. In children aged 1-5 years, mean sCr-Jaffe was higher than sCr-enz (44.0 ± 5.0 vs. 27.7 ± 7.3 µmol/L, P < 0.001), leading to lower eGFR-Jaffe (83.2 ± 9.0 vs. 137.9 ± 27.1 mL/min/1.73m2, P < 0.001) and lower Vdose-Jaffe (44.7 ± 2.5 vs. 53.5 ± 5.1 mg/kg/24 h, P < 0.001). CONCLUSION: Based on these findings, young children may be at risk for vancomycin under-treatment. Further research is needed to define the more accurate sCr assay in young children treated with renally excreted drugs.

Pediatric within-day biological variation and quality specifications for 38 biochemical markers in the CALIPER cohort.

BACKGROUND: Studies of biological variation provide insight into the physiological changes that occur within and between study participants. Values obtained from such investigations are important for patient monitoring and for establishing quality specifications. In this study we evaluated the short-term biological variation of 38 chemistry, lipid, enzyme, and protein analytes in a pediatric population, assessed the effect of age partitions on interindividual variation, and compared the findings to adult values. METHODS: Four plasma samples each were obtained within 8 h from 29 healthy children (45% males), age 4-18 years. Samples were stored at -80 °C and analyzed in 3 batches, with samples from 9-10 study participants per batch. Within-person and between-person biological variation values were established using nested ANOVA after exclusion of outliers by use of the Tukey outlier test. Analytical quality specifications were established with the Fraser method. RESULTS: Biological variation coefficients and analytical goals were established for 38 analytes. Age partitioning was required for 6 analytes. Biological variation characteristics of 14 assays (37%) were distinct from adult values found in the Westgard database on biological variation. Biological variation characteristics were established for 2 previously unreported analytes, unconjugated bilirubin and soluble transferrin receptor. CONCLUSIONS: This study is the first to examine biological variation and to establish analytical quality specifications on the basis of biological variation for common assays in a pediatric population. These results provide insight into pediatric physiology, are of use for reference change value calculations, clarify the appropriateness of reference interval use, and aid in the development of quality management strategies specific to pediatric laboratories.

Validity of establishing pediatric reference intervals based on hospital patient data: a comparison of the modified Hoffmann approach to CALIPER reference intervals obtained in healthy children.

OBJECTIVES: To compare pediatric reference intervals calculated using hospital-based patient data with those calculated using samples collected from healthy children in the community as part of the CALIPER study. METHODS: Hospital-based data for 13 analytes (calcium, phosphate, iron, ALP, cholesterol, triglycerides, creatinine, direct bilirubin, total bilirubin, ALT, AST, albumin and magnesium), measured on the Vitros 5600, collected between 2007 and 2011 were obtained. The data for each analyte were partitioned by age and gender as previously defined by the CALIPER study. Outliers in each partition were removed using the Tukey method. The cumulative distribution function (cdf) was then determined for each analyte value following which, the inverse cdf values of a standard Gaussian distribution were calculated. The analyte values were plotted against the inverse cdf of the standard Gaussian distribution. Piece-wise regression determined the linear portion of the resulting graph using the statistical software R. Linear regression determined an equation for the linear portion in each partition and reference intervals were calculated by extrapolating to identify the 2.5th and 97.5th centiles in each partition based on the inverse cdf values (which would correspond to the values -1.96 and 1.96 of the Gaussian distribution). Using the 90% confidence intervals for the reference intervals defined by CALIPER and the Reference Change Value (RCV) as the criteria, these calculated reference intervals were compared to those reported previously by CALIPER. Reference samples were also measured on the Vitros 5600 analyzer in an attempt to validate the calculated reference intervals. RESULTS: In general, the reference intervals calculated from hospital-based data were generally wider than those calculated by CALIPER. None of the reference intervals calculated using the Hoffmann approach fell completely within the 90% confidence intervals calculated by CALIPER. CONCLUSIONS: These results suggest that calculating pediatric reference intervals from hospital-based data may be useful, as a guide, in some cases but will likely not replace the need to establish reference intervals in healthy pediatric populations.

Acute olanzapine overdose in a toddler: a case report.

We describe a 17-month-old female presented with an acute overdose of olanzapine, an atypical antipsychotic. She displayed prolonged extrapyramidal symptoms as compared with that in previous reports and prolactin levels above the upper limits of normal ranges. This is the first report to measure serum prolactin levels in an olanzapine-overdosed toddler and the second to calculate olanzapine's elimination half-life.

Pediatric reference intervals: challenges and recent initiatives.

The clinical laboratory plays a critical role in healthcare delivery by providing objective data on specific biomarkers that directly aid in the diagnosis and monitoring of a wide range of clinical disorders. Reliable and accurate reference intervals for laboratory analyses are integral for correct interpretation of clinical laboratory test results and, therefore, for appropriate clinical decision-making. Ideally, reference intervals should be established based on a healthy population and stratified for key covariates including age, gender and ethnicity. However, establishing reference intervals can be challenging as it requires the collection of large numbers of samples from healthy individuals. This challenge is further augmented in pediatrics, where dynamic changes due to child growth and development markedly affect circulating levels of disease biomarkers. As a result, even larger reference populations are required to reliably calculate reference intervals. In this review, we outline the challenges specific to establishing pediatric reference intervals and highlight recent initiatives aimed at closing existing gaps in current knowledge. We also outline recommended approaches to the development of reference intervals and detail several alternative approaches. Finally, reference intervals for emerging and novel biomarkers of pediatric disease are discussed along with a number of potential alternative sample types.

Complex biological pattern of fertility hormones in children and adolescents: a study of healthy children from the CALIPER cohort and establishment of pediatric reference intervals.

BACKGROUND: Pediatric endocrinopathies are commonly diagnosed and monitored by measuring hormones of the hypothalamic-pituitary-gonadal axis. Because growth and development can markedly influence normal circulating concentrations of fertility hormones, accurate reference intervals established on the basis of a healthy, nonhospitalized pediatric population and that reflect age-, gender-, and pubertal stage-specific changes are essential for test result interpretation. METHODS: Healthy children and adolescents (n = 1234) were recruited from a multiethnic population as part of the CALIPER study. After written informed parental consent was obtained, participants filled out a questionnaire including demographic and pubertal development information (assessed by self-reported Tanner stage) and provided a blood sample. We measured 7 fertility hormones including estradiol, testosterone (second generation), progesterone, sex hormone-binding globulin, prolactin, follicle-stimulating hormone, and luteinizing hormone by use of the Abbott Architect i2000 analyzer. We then used these data to calculate age-, gender-, and Tanner stage-specific reference intervals according to Clinical Laboratory Standards Institute C28-A3 guidelines. RESULTS: We observed a complex pattern of change in each analyte concentration from the neonatal period to adolescence. Consequently, many age and sex partitions were required to cover the changes in most fertility hormones over this period. An exception to this was prolactin, for which no sex partition and only 3 age partitions were necessary. CONCLUSIONS: This comprehensive database of pediatric reference intervals for fertility hormones will be of global benefit and should lead to improved diagnosis of pediatric endocrinopathies. The new database will need to be validated in local populations and for other immunoassay platforms as recommended by the Clinical Laboratory Standards Institute.

Marked biological variance in endocrine and biochemical markers in childhood: establishment of pediatric reference intervals using healthy community children from the CALIPER cohort.

BACKGROUND: Reference intervals are indispensable in evaluating laboratory test results; however, appropriately partitioned pediatric reference values are not readily available. The Canadian Laboratory Initiative for Pediatric Reference Intervals (CALIPER) program is aimed at establishing the influence of age, sex, ethnicity, and body mass index on biochemical markers and developing a comprehensive database of pediatric reference intervals using an a posteriori approach. METHODS: A total of 1482 samples were collected from ethnically diverse healthy children ages 2 days to 18 years and analyzed on the Abbott ARCHITECT i2000. Following the CLSI C28-A3 guidelines, age- and sex-specific partitioning was determined for each analyte. Nonparametric and robust methods were used to establish the 2.5th and 97.5th percentiles for the reference intervals as well as the 90% CIs. RESULTS: New pediatric reference intervals were generated for 14 biomarkers, including α-fetoprotein, cobalamin (vitamin B12), folate, homocysteine, ferritin, cortisol, troponin I, 25(OH)-vitamin D [25(OH)D], intact parathyroid hormone (iPTH), thyroid-stimulating hormone, total thyroxine (TT4), total triiodothyronine (TT3), free thyroxine (FT4), and free triiodothyronine. The influence of ethnicity on reference values was also examined, and statistically significant differences were found between ethnic groups for FT4, TT3, TT4, cobalamin, ferritin, iPTH, and 25(OH)D. CONCLUSIONS: This study establishes comprehensive pediatric reference intervals for several common endocrine and immunochemical biomarkers obtained in a large cohort of healthy children. The new database will be of global benefit, ensuring appropriate interpretation of pediatric disease biomarkers, but will need further validation for specific immunoassay platforms and in local populations as recommended by the CLSI.