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Pediatric Reference Intervals Eight Edition Edward C.C. Wong, MD, FCAP Carlo Brugnara, MD Joely A. Straseski, PhD, DABCC Mark D. Kellogg, PhD, MT(ASCP), DABCC Khosrow Adeli, PhD, FCACB, DABCC AcademicPressis animprintofElsevier 125LondonWall,LondonEC2Y 5AS,UnitedKingdom 525BStreet,Suite1650,SanDiego,CA92101, UnitedStates 50HampshireStreet,5thFloor,Cambridge,MA 02139,UnitedStates TheBoulevard,LangfordLane,Kidlington,OxfordOX51GB,UnitedKingdom Copyright©2021 ElsevierInc.Allrights reserved. Nopart ofthispublicationmaybereproduced ortransmittedinany formorbyany means,electronic or mechanical,including photocopying,recording,or anyinformation storageandretrievalsystem, without permissioninwritingfromthePublisher.Detailsonhowtoseek permission, furtherinformation aboutthe Publisher’spermissions policies andourarrangements withorganizations suchastheCopyrightClearance CenterandtheCopyrightLicensingAgency,canbefoundatourwebsite:www.elsevier.com/permissions. Thisbookandtheindividual contributionscontainedinitareprotectedunder copyrightbythePublisher (otherthanasmaybenotedherein). Notices Knowledgeandbestpracticeinthisfieldareconstantlychanging. Asnewresearch andexperience broaden ourunderstanding, changesinresearchmethods,professionalpractices,or medicaltreatment maybecome necessary. Practitionersandresearchers mustalwaysrelyontheirown experienceandknowledgeinevaluating and usingany information,methods,compounds,orexperiments describedherein.In usingsuchinformation ormethodstheyshouldbemindfuloftheirownsafety andthesafetyofothers,includingpartiesforwhom theyhaveaprofessional responsibility. Tothefullestextentofthelaw,neitherthePublisher,northeauthors,contributors, oreditors, assumeany liabilityforany injuryand/ordamagetopersonsorproperty asamatterofproductsliability,negligenceor otherwise,orfromany useoroperation ofany methods,products, instructions,or ideascontainedinthe materialherein. AboutAACC Dedicatedtoachievingbetterhealththroughlaboratorymedicine,AACCbringstogethermorethan50,000 clinicallaboratoryprofessionals,physicians, research scientists,andbusinessleadersfrom aroundthe worldfocused onclinicalchemistry,molecular diagnostics,mass spectrometry,translationalmedicine,lab management,andotherareasofprogressinglaboratory science.Since1948,AACChasworkedtoadvance thecommoninterests ofthefield,providingprograms thatadvancescientificcollaboration,knowledge, expertise,andinnovation. Formoreinformation,visit www.aacc.org. Publishedincooperationwith AACC LibraryofCongressCataloging-in-Publication Data Acatalog recordforthisbookisavailablefrom theLibraryofCongress BritishLibraryCataloguing-in-Publication Data Acatalogue recordforthisbookis availablefromtheBritish Library ISBN:978-0-12-817939-0 Forinformation onallAcademicPress publicationsvisitourwebsiteat https://www.elsevier.com/books-and-journals Publisher:StacyMasucci Acquisitions Editor:Ana ClaudiaAbadGarcia EditorialProjectManager: MonaZahir ProductionProjectManager: KiruthikaGovindaraju CoverDesigner: ChristianJ.Bilbow TypesetbyTNQTechnologies We dedicate this book to our children and grandchildren. We hope that children worldwide will benefit from this eighth edition of Pediatric Reference Intervals (formerly Pediatric Reference Ranges) Foreword Thisinvaluablevolumeonpediatriclaboratorymedicineisaveryimportantcontributionto patient care, now made even more useful by the addition of a greatly expanded chemistry section and more complete hematology and coagulation reference ranges. Every children’s hospital, pediatric department, and clinical laboratory should have this well-designed and easy-to-read manual close at hand. The editors are to be commended for their splendid addition to the quality of laboratory diagnosis. David G. Nathan, MD DanaeFarber Cancer Institute Boston, Massachusetts xix Preface The need for pediatric reference intervals is quite evident, as children and adolescents undergo a series of remarkable changes in growth, organ development, and sexual maturity from the time they are born to the time they become adults. For example, neonates and prematureinfantsstartoffwithimmaturehepatic,renal,andpulmonaryfunctionwhichcan affect the way a wide variety of medications are metabolized. The rapid endocrine changes evidentduringpubertyareatestamenttotheneedforwell-definedreferenceintervalsinthis age group. Thus, without appropriate reference intervals, laboratory testing becomes an inexact endeavor in futility. fi How Do We Approach the De nition of Normal Reference Intervals? In the ideal situation, samples would be collected directly from a large number of healthy childrenofallagegroups,thelaboratorywouldtesteachsample,andthoseresultswouldbe usedtodeterminestatisticallyrelevantreferenceintervalsfortheappropriateagepartitions. However,weknowthisisnotaneasytask.Childrenareconsideredvulnerablesubjectsfroma researchperspectiveand,therefore,havelimitationsonthetotalvolumeofbloodthatcanbe safely collected from them. Strict protocols for consent/assent to participate in research studies may be challenging to administer to children and require parent or guardian involvement.Additionally,participantsneedtobecarefullyscreenedfordisordersthatmight bias any measured results (1). The difficult nature of phlebotomy, particularly in younger children, can also cause emotional stress on parents who might not want their child to participate in a potentially painful procedure with no immediate benefit. Because of these andotherpracticalchallenges,itisoftendifficulttoobtainadequatesamplevolumesfromat least 120 healthy individuals to achieve a statistically accurate normative reference interval for an age partition. That challenge is compounded by the need for multiple age and sex partitions in growing and maturing children. Thus, relatively large studies with “healthy” volunteers are particularly difficult to perform but provide reassurance in the statistical determination of reference intervals that typically encompass the 2.5th to 97.5th percentiles of the reference population data (1). Statistical Approaches Used to Determine Reference Intervals Inlieuofthepreferredapproachofprospectivecollectionoflargesamplenumbersdescribed above, several investigators have derived or used statistical methods on large databases of existing laboratory results to retrospectively determine appropriate reference intervals. One notable approach that has been included in previous editions of this book is the Hoffmann approximation (2). This approach typically uses either Chauvenet’s or Dixon’s criteria for removing outliers and involves plotting % cumulative frequency versus the laboratory xxi xxii Preface value (or log of the value, if non-Gaussian distribution). Using this approach, one obtains a straight linetypically within the central portion of theplotted curve. This straight line can beextrapolatedtoprovidethe2.5thand97.5thpercentilesforthepopulationbeingstudied. An example for total iron-binding capacity is shown in Fig. 1(3). This approach is simplistic overallandhasparticularappealinpopulationswithlimiteddataavailablefromfreshsample collections from volunteers, such as pediatrics. Disadvantages include the need to be very selective in the population being considered since patients typically have testing performed duetoaclinicalconcernandmaynotrepresenta“healthy”population.Otherdisadvantages include the need to carefully select appropriate age interval(s) and the need for a very large numberofdatapointsinordertoperformthesestatisticalcalculationsforreferenceinterval derivation.There hasbeen a recentvalidation oftheHoffmann approximation using a large database from a nationwide chain of clinical reference laboratories in the United States, without exclusions or filtering (4). A major criticism of the Hoffman approximation is the observation of narrower than expected reference intervals (5). There have, therefore, been a number of statistical ap- proaches that have attempted to improve upon the Hoffman approximation. These include the Bhattacharya graphical method which involves the identification of Gaussian distribu- tions within a distribution (6). Another is a computational (nongraphical) strategy using maximum likelihood through the expectationemaximization algorithm (7). As reviewed by Holmes and Buhr (5), however, all of these methods should be considered to be “indirect” estimates of reference intervals in healthy children and should be verified using data from such individuals. Another method that has recently been developed is the use of continuous pediatric reference curves for chemistry analytes (8). The advantages of this approach are that it providesacontinuumofupperandlowerreferenceintervalsandavoidstheuseofreference Figure1 Hoffmannplotfortotalironebindingcapacity.ReprintedfromFig.1fromRef.(3)withpermissionfrom Elsevier. Preface xxiii Figure 2 Example of continuous vs. Noncontinuous reference intervals and comparison of continuous versus partitionedreferenceintervalsforBUN/creationratiosfromages0to19years.Referencevalues,continuous referenceinterval,andpartitionedreferenceintervalsarecodedineitherpink(females)orblue(males). Partitionedreferenceintervalsforbothsexesareinblack.Shadedareasrepresent95%confidenceintervals. ReprintedfromFig.1D(Ref.(9))withpermissionfromElsevier. intervals that are arbitrarily delineated which may lead to misclassification close to age “cutoff” points. Current laboratory information systems, however, will need future en- hancements to incorporate these curves into routine laboratory reports (See Fig. 2) (9). fi Method-Speci c Differences Anotherpotentialcomplicationtoconsiderwhendeterminingpediatricreferenceintervalsis technology.Giventheplethoraofassaymethodsandinstrumentsavailableforpurchase,itis extremely unlikely that every laboratory will use the same method or analyzer for measure- mentofaparticularanalyte.Thecruxofthisconcernisthatthemajorityofanalytesarenot standardized among methods, resulting in values that cannot be compared well between laboratories.Agoodexampleisinstrumentationthatquantitatesalkalinephosphataselevels. Recent proficiency testing data indicate mean values differed among commercial platforms by as much as 300%. Therefore, the method or commercial platform used to measure analytes used in pediatric reference interval determinations should be carefully considered and noted before intervaluseoradoptionbyalaboratory.Italsospeakstothecriticalneedformethod-specific reference intervals. Conclusion Itisveryclearthatmuchworkandthoughtgoesintothedevelopmentofpediatricreference intervals including careful consideration and screening of the population studied, the developmental status of the population, the instrumentation used, and the statistical xxiv Preface methods employed. Future advances in laboratory information systems may allow for reporting of continuous pediatric reference intervals to better provide accurate reference intervalsforpatients.Referenceintervalsprovidecontexttomeasuredlaboratoryvaluesand allowforthecomparisonbetweenhealthanddisease.Theirimportance,therefore,cannotbe overstated. References 1. AdeliK,HigginsV,TrajcevskiK,White-AlHabeebN.TheCanadianlaboratoryinitiativeonpediatric referenceintervals:aCALIPERwhitepaper.CritRevClinLabSci2017;54:358e413. 2. HoffmannRG.Statisticsinthepracticeofmedicine.JAMA1963;185:864e873. 3. Soldin OP, Bierbower LH, Choi JJ, Choi JJ, Thompson-Hoffman S, Soldin SJ. Serum iron, ferritin, transferrin, total iron binding capacity, hs-CRP, LDL cholesterol and magnesium in children; new referenceintervals usingtheDadeDimensionClinicalChemistrySystem. ClinChimActa2004;342: 211e217. 4. Katayev A, Balciza C, Seccombe DW. Establishing reference intervals for clinical laboratory test re- sults:isthereabetterway?AmJClinPathol2010;133:180e186. 5. Holmes DT, Buhr KA. Widespread Incorrect Implementation of the Hoffmann Method, the Correct Approach,andModernAlternatives.AmJClinPathol2019;151:328e336. 6. Bhattacharya C. A simple method of resolution of a distribution into Gaussian components. Biometrics1967;23:115e135. 7. RednerRA,WalkerHF.Mixturedensities,maximumlikelihoodandtheEMalgorithm.SIAMReview 1984;26:195e239. 8. HoqM,MatthewsS,KarlaftisV,BurgessJ,CowleyJ,DonathS,CarlinJ,YenT,IgnjatovicV,Monagle P;HAPPIKidsStudyTeam.Referencevaluesfor30commonbiochemistryanalytesacross5different analyzersinneonatesandchildren30daysto18yearsofage.ClinChem2019;65:1317-1326. 9. BohnMK,HigginsV,AdeliK.CALIPERpaediatricreferenceintervalsfortheureacreatinineratioin healthychildren&adolescents.ClinBiochem2020;76:31e34. Introduction Welcome to the eighth edition of Pediatric Reference Intervals. This edition follows the publication of its predecessor in 2011, which was the last edition published by AACC Press. WearehappythatthistextbookhasfounditsnewhomeinAcademicPressandtheElsevier family.Theeightheditionwitnessedaconsiderablerefreshingoftheeditorialteamwiththe addition of three new editors: Joely A. Straseski, Associate Professor (Clinical) in the Department of Pathology at the University of Utah School of Medicine, and Section Chief of Clinical Chemistry, Medical Director of Endocrine, and Codirector of Automated Core Laboratories at ARUP Laboratories. Dr. Straseski is the director of the CHILDx (Children’s Health Improvement through Laboratory Diagnostics) biorepository of samples from healthy children. Mark D. Kellogg, Director for Quality Programs and Associate Director of Chemistry in the Department of Laboratory Medicine at Boston Children’s Hospital and Assistant Professor of Pathology at Harvard Medical School. Khosrow Adeli, Head of Clinical Biochemistry at The Hospital for Sick Children and Professor at the Departments of Biochemistry, Physiology, and Laboratory Medicine and Pathobiology at the University of Toronto in Toronto, Canada. He is the principal investigator of the CALIPER (Canadian Laboratory Initiative on Pediatric Reference Intervals) project (www.caliperproject.org; www.caliperdatabase.org). This eighth edition of Pediatric Reference Intervals is a near-complete update of the analytespublishedintheprioredition.Thisneweditionhasbeensignificantlystrengthened inhematologywiththeinclusionofseveralnewdatasetsandexpandedincoagulationwith the inclusion of several additional analytes. In choosing which publications and data to include in the book, we prioritized published studies that included normal pediatric pop- ulations and currently used instrumentation. Chemistry analytes have been expanded and reviewed for clinical relevance. A scoring/metric system was developed to evaluate the available literature based on the following criteria: age and type of publication, population size,whetherethnicityandmethodplatformwerereported,andavailability/frequencyofuse of the method or platform. Scores were used to determine which publications to include when multiple were available. Where appropriate, the reader is directed to the original publicationfordetailsthatexceedwhatiscoveredinthisbook.Similartotheseventhedition, we have kept the same user-friendly format with each analyte having the same layout. We hope this provides easy access to key information such as sample type, methodology used, sourcereference,patientpopulation,andthestatisticalbasisonwhichthereferenceintervals were derived. xxv xxvi Introduction As a reminder to those that use reference intervals to evaluate clinical test results, refer- ence intervals are meant as guidelines only and cannot be used to definitively diagnose a child’s disease state without correlating test results with the clinical condition. This is particularly important because values for both healthy and sick patients frequently overlap and interpretation within the context of the clinical situation is critical. Weareindebtedtotheassistanceprovidedbytheresidents,fellows,andtraineesthathave helpedcompiletheliteratureandtheircriticalanalysisoftherangesprovided:GraceKroner, PhD (University of Utah), Shannon Steele (CALIPER, The Hospital for Sick Children), Mary Kathryn Bohn, PhD candidate (University of Toronto), Li Zha, PhD (Boston Children’s Hospital), and MAJ Angela Davis, PhD (Boston Children’s Hospital). This edition would not have been possible without their contributions. WewouldalsoliketothankourElsevierProjectManagers,AnnaDubnowandMonaZahir for their assistance with this updated edition. We want to express our gratitude to Steven J. Soldinforhavingledtheeditorialteaminthepriorseveneditions.WewouldalsothankMs. LinaNohforherexcellentadministrativehelpincompilingandeditingthehematologyand coagulation sections. Edward C.C. Wong, MD, FCAP Carlo Brugnara, MD Joely A. Straseski, PhD, DABCC Mark D. Kellogg, PhD, MT(ASCP), DABCC Khosrow Adeli, PhD, FCACB, DABCC

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