Clin Chem Lab Med 2018; 56(2): 327–340
Victoria Higgins, Angela W.S. Fung, Man Khun Chan, Joseph Macri and Khosrow Adeli*
Pediatric reference intervals for 29 Ortho VITROS 5600 immunoassays using the CALIPER cohort of healthy children and adolescents https://doi.org/10.1515/cclm-2017-0349 Received April 21, 2017; accepted June 6, 2017; previously published online July 19, 2017
Abstract Background: Accurate reference intervals (RIs) based on a healthy pediatric population are essential for pediatric test result interpretation. The CALIPER project has recruited a large healthy cohort and completed a series of a priori studies to address gaps in pediatric RIs. As immunoassays from different manufacturers for endocrine and special chemistry markers are not standardized and show marked intermethod differences, direct RI studies are needed for each major analytical platform. Here, we report age- and sex-specific pediatric RIs for 29 immunoassays on the Ortho Clinical Diagnostics (Ortho) VITROS® 5600 analyzer. Methods: Health information and blood samples were collected from healthy pediatric subjects. Using the Ortho VITROS 5600 Integrated System MicroWell Technology, 29 biomarkers were measured. Analyte concentrations were partitioned by age and sex according to the Harris and Boyd method. After removing outliers, age- and sexspecific RIs and corresponding 90% confidence intervals were calculated according to CLSI guidelines. Results: All analytes required age partitioning except β-human chorionic gonadotropin (β-hCG), cancer antigen *Corresponding author: Khosrow Adeli, Clinical Biochemistry, DPLM, The Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada, E-mail:
[email protected]; CALIPER Program, Pediatric Laboratory Medicine, The Hospital for Sick Children, Toronto, ON, Canada; and Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada Victoria Higgins: CALIPER Program, Pediatric Laboratory Medicine, The Hospital for Sick Children, Toronto, ON, Canada; and Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada Angela W.S. Fung: Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada Man Khun Chan: CALIPER Program, Pediatric Laboratory Medicine, The Hospital for Sick Children, Toronto, ON, Canada Joseph Macri: Hamilton General Hospital, McMaster University, Hamilton, ON, Canada
15-3 (CA15-3), rubella immunoglobulin G (rubella IgG), and vitamin D. Several analytes including estradiol, progesterone, testosterone, follicle-stimulating hormone (FSH), luteinizing hormone (LH), free triiodothyronine (FT3), total triiodothyronine (TT3), total thyroxine (TT4), thyroid uptake, ferritin, intact parathyroid hormone (iPTH), total prostate-specific antigen (tPSA), free prostate-specific antigen (fPSA), cancer antigen 125 (CA125), creatine kinase MB (CK-MB), and myoglobin showed sex differences, observed mostly with the onset of puberty. Conclusions: Complex reference value trends were observed across the pediatric age range for several biomarkers examined on Ortho VITROS immunoassays. The availability of VITROS immunoassay RIs will enable accurate laboratory test interpretation and diagnosis for the pediatric population. As recommended by the CLSI EP28A3c guidelines, implementation of these RIs should be validated for each laboratory’s local pediatric population. Keywords: immunoassays; pediatric; reference intervals.
Introduction The interpretation of a laboratory test result is based on comparison to the corresponding reference interval (RI). RIs are commonly defined as the central 95% distribution of laboratory test results expected in a healthy reference population. Traditionally, there have been inconsistencies in pediatric RIs, potentially leading to misdiagnosis and unnecessary medical follow-up [1]. These gaps exist due to challenges faced when establishing RIs for the pediatric population. Marked growth, development and physiological changes in childhood and adolescence require stratifying RIs based on key covariates, including age and sex. Recruitment of a sufficiently large number of children and adolescents to stratify RIs based on age and sex is challenging and small sample sizes contribute to the lack of robust statistical data. Additionally, younger subjects can only provide a small volume of blood, limiting the number of laboratory tests able to be performed on each subject. Therefore, there has been a lack of accurate pediatric RIs established from an appropriate, large healthy population. Brought to you by | University of Toronto-Ocul Authenticated Download Date | 10/8/18 9:23 PM
328 Higgins et al.: Pediatric reference intervals for 29 Ortho VITROS 5600 immunoassays The Canadian Laboratory Initiative on Pediatric Reference Intervals (CALIPER) project is a Canada-wide research initiative that has been successfully addressing these gaps by developing a comprehensive database of age- and sex-specific pediatric RIs (www.caliperproject.ca). To date, CALIPER has established RIs for over 100 analytes including common chemistry markers, proteins, lipids and enzymes [2], specialty endocrine markers [3], fertility hormones [4], cancer biomarkers [5], vitamins [6], metabolic disease biomarkers [7], testosterone indices [8], and specialized biochemical markers [9] using Abbott Architect assays. Therefore, CALIPER RIs were initially only applicable to laboratories using the Abbott Architect platform, limiting their nationwide implementation. To ensure CALIPER RIs are widely available for laboratories using other commonly used analytical systems, CALIPER performed a series of transference studies to directly transfer and verify common chemistry marker RIs through a method comparison analysis. As a result, CALIPER RIs are now available for assays on several other analytical platforms, including Beckman Coulter DxC800, Beckman Coulter AU, Ortho VITROS 5600, Roche cobas 6000, Roche Modular P, and Siemens Vista 1500 [10–13]. Between-assay standardization has been achieved for several chemistry analytes through development of reference methods and standard reference materials. This allows RIs to often be successfully transferred using regression equations developed through a method comparison analysis. However, the availability of reference methods and materials is limited for immunoassays, where standardization has only been successful for a few analytes [14]. This results in greater method-to-method differences for immunoassays, and therefore transference of RIs from one manufacturer to another may not always be feasible. The lack of assay standardization has the potential to greatly impact adequate test result interpretation leading to erroneous diagnosis and/or treatment, as healthcare providers are often unaware of differences in results obtained from different analytical methods. Therefore, both laboratory professionals and manufacturers of analytical assays must put forth effort to standardize their methods to improve accuracy, consistency, and comparability. Until standardization occurs, assays that produce variable results between manufacturers must have assay-specific RIs established. Therefore, for immunoassays, CALIPER develops de novo population-based RIs through direct RI studies [15]. Here, we expand the applicability of the CALIPER database by establishing age- and sex-specific pediatric RIs for 29 immunoassays on the Ortho VITROS 5600 Integrated System (Ortho Clinical Diagnostics). Determining RIs specific for Ortho VITROS immunoassays will allow laboratories using these assays to interpret
pediatric laboratory test results using evidence-based, robust RIs determined specifically for these assays.
Materials and methods Participant recruitment and sample acquisition This study was approved by the Institutional Review Board at the Hospital for Sick Children, Toronto, Canada. Serum samples were selected from the CALIPER biobank of healthy children and adolescents. Participant recruitment for CALIPER has been described previously [2]. Briefly, healthy children and adolescents aged 1 to
