Point-of-Care Quantitative Measure ofGlucose-6-Phosphate DehydrogenaseEnzyme DeficiencyVinod K. Bhutani, MDa, Michael Kaplan, MDb, Bertil Glader, MD, PhDa, Michael Cotten, MDc, Jairus Kleinert, PhDd,Vamsee Pamula, PhDe

abstract BACKGROUND AND OBJECTIVES:Widespread newborn screening on a point-of-care basis could preventbilirubin neurotoxicity in newborns with glucose-6-phosphate dehydrogenase (G6PD)deficiency. We evaluated a quantitative G6PD assay on a digital microfluidic platform bycomparing its performance with standard clinical methods.

METHODS: G6PD activity was measured quantitatively by using digital microfluidic fluorescenceand the gold standard fluorescence biochemical test on a convenience sample of 98 discardedblood samples. Twenty-four samples were designated as G6PD deficient.

RESULTS:Mean6 SD G6PD activity for normal samples using the digital microfluidic method andthe standard method, respectively, was 9.7 6 2.8 and 11.1 6 3.0 U/g hemoglobin (Hb),respectively; for G6PD-deficient samples, it was 0.8 6 0.7 and 1.4 6 0.9 U/g Hb. Bland-Altmananalysis determined a mean difference of –0.96 6 1.8 U/g Hb between the digital microfluidicfluorescence results and the standard biochemical test results. The lower and upper limits forthe digital microfluidic platform were 4.5 to 19.5 U/g Hb for normal samples and 0.2 to 3.7 U/gHb for G6PD-deficient samples. The lower and upper limits for the Stanford method were 5.5 to20.7 U/g Hb for normal samples and 0.1 to 2.8 U/g Hb for G6PD-deficient samples. Themeasured activity discriminated between G6PD-deficient samples and normal samples with nooverlap.

CONCLUSIONS: Pending further validation, a digital microfluidics platform could be an accuratepoint-of-care screening tool for rapid newborn G6PD screening.

WHAT’S KNOWN ON THIS SUBJECT: Glucose-6-phosphate dehydrogenase deficiency remainsa global as well as a North American burden forextreme hyperbilirubinemia and kernicterus andis often unpredictable during the first few daysafter birth. Newborn screening for this enzymedeficiency is not universally available butdebated.

WHAT THIS STUDY ADDS: Point-of-care screening,using digital microfluidics, provides accurate,low blood volume, and affordable technology forrapid newborn glucose-6-phosphatedehydrogenase enzyme screening that couldguide clinicians before infants’ discharge fromwell-child nurseries and meet existing AmericanAcademy of Pediatrics’ recommendations.

aDepartment of Pediatrics, Stanford University School of Medicine, Stanford, California; bFaculty of Medicine ofthe Hebrew University, Jerusalem, Israel; cDepartment of Pediatrics, Duke University School of Medicine, Durham,North Carolina; dAdvanced Liquid Logic, Durham, North Carolina; and eBaebies, Inc, Durham, North Carolina

Dr Bhutani conceptualized the study, supervised data collection, and revised the final manuscript;Dr Kaplan participated in the study as an advisor, reviewed the data collection, and revised the finalmanuscript; Dr Glader assisted in the conceptual design of the study, supervised data collectionthrough the assay at Stanford Hillview Laboratory, and revised the final manuscript as submitted;Dr Cotten conceptualized the study; Dr Kleinert conceptualized the technical design, developed theassay, and generated the program protocols for performing the glucose-6-phosphatedehydrogenase assays on the digital microfluidic cartridges. Dr Pamula conceptualized anddesigned the study, directed development of the digital microfluidic system, and drafted the initialmanuscript; he had no influence on the clinical design of the study. All authors approved the finalmanuscript as submitted.

The content of this article is solely the responsibility of the authors and does not necessarilyrepresent the official views of the National Institutes of Health.

www.pediatrics.org/cgi/doi/10.1542/peds.2015-2122

DOI: 10.1542/peds.2015-2122

Accepted for publication Aug 5, 2015

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Neonatal jaundice is a commonlyoccurring condition, with some degreeof jaundice being noticed in up to 80%of otherwise healthy, term and late-preterm newborns.1,2 Generally, thejaundice has a benign outcome whenscreened for and treated in a timelymanner. An unpredictable number ofnewborns, particularly those withglucose-6-phosphate dehydrogenase(G6PD) deficiency, can adverselyprogress with rapidity to extremehyperbilirubinemia with signs of acutebilirubin encephalopathy. Extremeneonatal hyperbilirubinemia iseffectively treated by phototherapy,with exchange transfusion as a backuptreatment modality. As a result,kernicterus and exchange transfusionsare minimally encountered inindustrialized countries withfunctional and intact health caresystems. Conversely, delay in seekinghealth care, rapid onset of progressivehyperbilirubinemia, and delayed orlack of access to effectivephototherapy and/ or exchangetransfusion (such as have beenreported from developing or low- andmiddle-income countries) can result inan infant developing the potentiallytragic consequences of lifelongchoreoathetotic cerebral palsy,otherwise known as kernicterus.3–5

G6PD deficiency is an X-linkedcondition encountered amonghundreds of millions of individuals.Originally confined to its indigenousdistribution, including Africa, theMediterranean Basin, the MiddleEast, and extending through Asia tothe Far East, immigration patterns,the slave trade and modern ease oftravel have made it a condition thatmay be encountered virtuallyworldwide. G6PD deficiency isa condition not only of low- andmiddle-income countries4 but also ofhigh-income, industrializedcountries.6 In the newborn, G6PDdeficiency is associated with a highincidence of neonatalhyperbilirubinemia and especiallywith sudden, exponential, andunpredictable increases in the total

serum bilirubin level to extremeconcentrations. G6PD deficiencyappears high on lists of knownetiologies of newborns withkernicterus or extremehyperbilirubinemia.7–10 Screeningfor G6PD deficiency in the newbornperiod has been recommended bythe Working Committee of the WorldHealth Organization to pinpointaffected newborns at high risk forextreme hyperbilirubinemia; the goalis to prevent exposure of theseinfants to known triggers ofhemolysis and to facilitate theapproach to appropriate medicalfacilities should hyperbilirubinemiadevelop and before the onset ofbilirubin neurotoxicity.

The present study tested andevaluated a digital microfluidicsplatform developed and programmedto measure G6PD activity from wholeblood in a point-of-care setting,including all steps of analysis, fromwhole blood lysis, reagent preparation,sample processing, mixing, dilution,incubation, and fluorescence detectionto waste handling; the objective was todetermine how to best describe itspotential as a screening device. Digitalmicrofluidic technology enables allsteps of analysis from samplingthrough waste handling ona disposable cartridge. Performance ofimmunoassays, enzyme assays, andDNA analyses by using small amountsof sample and reagents in a user-friendly, point-of-care device makesthis technology potentially attractiveto newborn screening in a globalsetting.11

METHODS

Blood Samples

Discarded and deidentified wholeblood samples (N = 98) wereobtained under an institutionalreview board–approved protocolfrom newborn and older children(cared for at Lucile PackardChildren’s Hospital) and adultpatients (cared for at StanfordHospital). The discarded samples

were made available from randomsamples tested at the Stanfordclinical laboratory, and the knownG6PD-deficient samples were fromthe Hillview RBC Special StudiesLaboratory. Gender of the samplesources was documented. Eachsample was collected in EDTA-coated tubes and stored at 4°C untilanalysis. All the samples werequantitatively analyzed for G6PDactivity within 72 hours ofcollection by using the standarddiagnostic method at the StanfordHillview laboratory. Within 24hours of collection, the samesamples were analyzed by using thedigital microfluidic platform forG6PD activity at the StevensonLaboratory at Stanford. Based onprevious experiences, it is knownthat red blood cell G6PD activity isstable for .21 days in bloodcollected in EDTA and stored at 4°C.12 All of our samples wereassayed well within these limits.The samples analyzed within 72hours of collection reflectedtechnician time available in theHillview laboratory.

Description of Digital MicrofluidicAnalyzer and Sample-Input Cartridge

A disposable, single-use digitalmicrofluidic cartridge for G6PD assayswas designed (Fig 1) with inputreservoirs for all assay reagents,calibrants, controls and samples, anda set of reservoirs for holding samples,reagents for G6PD, and waste locatedaround the edges of the cartridge.Droplets are dispensed from the liquidin the reservoirs by appropriateelectrode activation sequences.11

Before running the assays, silicone oilis used to fill the working space in thecartridge to prevent dropletevaporation and lubricate dropletmotion.13

A digital microfluidic analyzerfunctions to maintain the cartridgetemperature, supply voltage to drivethe droplets, and perform opticaldetection of the assays. Thetemperature is maintained at 37°C

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over the entire cartridge and for theduration of the assay. The analyzercontrols individual electrodes on thecartridge to perform all dropletoperations, including dispensing,mixing, incubation, and sampledisposal. The custom-built opticaldetector on the device features 2channels: 1 channel for fluorescencereadings at 360 nm excitation/460 nmemission and 1 channel for absorbancereadings from 490 from 710 nm.

Reagents

G6PD controls were obtained fromTrinity Biotech (Bray, Ireland). Trisbuffer, bovine serum albumin, sodiumcarbonate, sodium bicarbonate,Tween-20, magnesium chloride,maleimide, b-nicotinamide adeninedinucleotide phosphate (NADP),D-glucose-6-phosphate, andb-nicotinamide adenine dinucleotidephosphate hydrate (NADPH) wereobtained from Sigma-AldrichCorporation (St Louis, MO). Moleculargrade water was obtained from FisherScientific (Pittsburgh, PA), and 5 cStsilicone oil was obtained from Gelest,Inc (Morrisville, PA).

The G6PD assay consisted of lysissolution (1.0% Tween-20 in distilledwater) for diluting the samples andlysing the red blood cells, substrate

solution (2.0-mM D-glucose-6-phosphate, 2.6-mM NADP, 2.4-mMmagnesium chloride, and 26-mMmaleimide in 100-mM Tris buffer atpH7.8 and containing 0.05% Tween-20), and fluorescence standard (100-mM NADPH in 50% (v/v) Tris bufferand 50% (v/v) lysis solution). Thecontrols (lyophilized blood hemolysatewith specified levels of G6PD activity)were reconstituted in a 0.05% (w/v)Tween-20 solution. The substrate andstandard were stored at 280°C, andthe lysis solution and control sampleswere stored at 4°C. The cartridge wasinserted into the analyzer deck asdescribed previously,11 and reagentsand samples were loaded onto thecartridge via a pipette. Briefly, for eachassay, 5 mL of whole blood waspipetted directly into the cartridge.After loading the samples andreagents, all subsequent assay stepswere performed by the analyzer. Theprotocols for performing the assays onthe microfluidic cartridges are brieflydescribed in the following section.Unless otherwise noted, all dropletswere 300 nL in volume.

G6PD Fluorescence Assay on a DigitalMicrofluidic Cartridge

A digital microfluidic cartridge wasloaded with 6 patient blood samples.

One droplet of each of the 6 wholeblood samples and 1 droplet ofnormal-level control were diluted ata ratio of 1:9 by mixing with a double-sized droplet of lysis solution, splittingoff and discarding a double-sizeddroplet, and mixing the remaining 300-nL droplet with a second double-sizeddroplet of lysis solution. This sequenceinvolves 2 consecutive 3-fold serialdilutions resulting in a 9-fold finaldilution of the samples. The resulting900-nL droplet was then further splitinto 2 fractions of 300 and 600 nL,respectively. The 600-nL droplet wasrouted to the detector, and thehemoglobin (Hb) concentration in thesample was determined by measuringabsorbance at 540 nm. The 300-nLdroplet was further diluted in lysissolution to a final ratio of 1:27 bymixing with a double-sized droplet oflysis solution and splitting off anddiscarding a double-sized droplet. Theremaining droplet was then mixedwith a droplet of substrate, and theG6PD in the samples converted NADPto NADPH. Fluorescence of the NADPHin the assays was measured at 360-nmexcitation and 460-nm emissionkinetically at 3 time points and wasrelated directly to the G6PD activityvia the rate of NADPH generationby using a linear calibration curvecreated by measuring thefluorescence of the NADPHstandard on each cartridge. Thereported activity was normalizedby using the Hb concentration. Ittook 17 minutes to run all 6samples simultaneously. This timecan be considerably reduced, butturnaround time was not theprimary objective of the study andtherefore no effort was made toshorten it.

G6PD Quantitative Assay at theStanford Red Cell Special StudiesLaboratory

Collected blood was washed 3 timesin isotonic NaCl and then filteredthrough a cellulose slurry to removeleukocytes and platelets. A 1:20destromatized hemolysate was then

FIGURE 1Digital microfluidic cartridge layout. A single-use cartridge is loaded with reagents, calibrants,control samples, and up to 6 patient samples.

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prepared by suspending 0.1 mL of50% filtered red blood cellsuspension into 0.9 mL ofa hemolyzing solution. The standardpremade hemolyzing solutioncontained the following: 3.3 mL of3-mM NADP, 0.05 mL ofmercaptoethanol, 10 mL of 10%EDTA pH 7.4, and distilled wateradded to a final volume of 1 L. G6PDactivity was measured according toa modification of the World HealthOrganization assay,12 whereby therate of NADP reduction to NADPH ismeasured when hemolysate is addedto a reaction mixture containingglucose-6-phosphate. Specifically,50 mL of a 1:20 hemolysate was addedto 1.0 mL of reaction mixture containing100-mM Tris-HCl, pH 8.0, 10-mMmagnesium chloride, and 0.3-mMNADP. The reaction was started byadding 100 mL of 10-mM glucose-6-phosphate. The rate of NADPreduction to NADPH was measuredby calculating the increase in opticaldensity at 340 nm at 25°C for 10minutes. Because enzyme activity isdependent on temperature, acorrection factor is necessary toadjust for these variations when theassays are run at differenttemperatures, such as in this study. Inthe case of G6PD, the correctedactivity at 25°C compared with 37°Cis 0.559.

RESULTS

G6PD was measured on 98 wholeblood samples from newborn infants1 to 3 days old (n = 52), olderchildren aged 4 days to 6 months (n =17), and adult patients (n = 29) whoserved as controls. Of these 98samples, 32 were from femalepatients, and 66 were from malepatients. Five (n = 5) newborn maleinfants (1–3 days old) were identifiedas G6PD deficient. Six (n = 6) olderchildren (aged 4 days–6 months)were identified as G6PD deficient;5 of these 6 children were male.Thirteen of the adults were identifiedas G6PD deficient (12 male patients).Patients with documented enzymatic

G6PD sufficiency, according tostandard enzymatic assays, served ascontrol subjects. Of this cohort, 24samples from male subjects weredesignated G6PD deficient, whereasthe remainder (control) had normalactivity. The G6PD-deficient andnormal samples were divided into2 distinct subgroups with nooverlap. The percentages ofG6PD-deficient and normalsamples should not be regarded asrepresentative cohorts but onlyrepresentative of a conveniencepopulation.

Comparison of G6PD activity obtainedby using the digital microfluidiccartridge and the Stanford DiagnosticLaboratory method are presented inFig 2. The solid line is not a fit butdrawn to depict a 45° line witha slope of 1. Mean 6 SD G6PD activityfor normal samples using the digitalmicrofluidic cartridge and theStanford method were 9.7 6 2.8 and11.1 6 3.0 U/g Hb, respectively; forthe G6PD-deficient samples, it was1.4 6 0.9 and 0.8 6 0.7 U/g Hb. Thelower and upper limits for the digitalmicrofluidic platform were 4.5 to 19.5U/g Hb for normal samples and 0.2 to3.7 U/g Hb for G6PD-deficient

samples. The lower and upper limitsfor the Stanford method were 5.5 to20.7 U/g Hb for normal samples and0.1 to 2.8 U/g Hb for G6PD-deficientsamples. Figure 3 illustrates that themean difference between these 2methods was –0.96 6 3.5 U/g Hb. Nodata points were rejected for outliers.Figure 4 summarizes all the data ina box plot to highlight thediscrimination of G6PD-deficientsamples from normal samples by usingdigital microfluidics; this metricassumes more importance for newbornscreening. The box represents the75th and 25th percentiles, and thewhiskers represent the minimum andmaximum G6PD activity values. Theyellow dot represents the mean activityin each case.

DISCUSSION

Although the World HealthOrganization has recommended G6PDscreening to identify newborns athigh risk in population groups witha male frequency .3% to 5%,14

implementation for regional orcommunity-wide newborn screeninghas been inconsistent among nationsand geographic locations.6,15

Screening on a national basis,

FIGURE 2Scatter plot of comparisons of G6PD activity obtained from the digital microfluidic method versusthe standard laboratory method at Stanford University.

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however, has been limited only toa few countries. Among thesecountries, the impact of newbornscreening regarding prevention ofkernicterus seems encouraging asrecently reviewed16 but has not beenrigorously tested other than throughhistorical data. One of the majorreasons for nonimplementation ofscreening programs is the cost of theproject for a universal quantitativeenzyme assay. Although the reagents

necessary are not expensive,manpower and administrativeoverhead remain the limiting factors.Mass screening with an affordabledigital microfluidic platform offersa solution to this problem, as thedevice completely automates all thesteps in performance of the assay. Forthis analysis, we specifically excludedfemale patients because there wereonly a few female subjects who werenot genotyped. Male subjects were

accurately categorized because theydivide into 2 distinct groups: deficientand normal. Female subjects, on theother hand, would divide into 3genetic categories: homozygousnormal, heterozygotes, andhomozygous deficient. Because ofnonrandom X chromosomeinactivation, heterozygotes would notdivide into a distinct group, but therewould be a continuum of G6PDactivity, from low (deficient)through intermediate to normal.17

It has been difficult to identifyheterozygotes by using biochemicalmethods, although values in theintermediate range suggest thepossibility of heterozygosity. Thepresent pilot study thus shows thefeasibility of the device for practicalclinical use in a point-of-caresetting for quantitative enzymeassay.

There are several screening testsfor G6PD deficiency, and most relyon qualitative assays for enzymeactivity. The fluorescent spot test(Trinity Biotech PLC, Bray, Ireland)and the CareStartTM RapidDiagnostic Tests (Access Bio Inc,Somerset, NJ) are the mostfrequently used qualitativescreening tests. The enzyme activitycutoff point is low (2.1 and 2.7 U/gHb, respectively), and only thosepatients with severe deficiencywould be detected. Almost allfemale heterozygotes would bemissed and reported as “normal.” Ina study of African-Americanneonates, G6PD findings in the“deficient group” were 2.7 6 1.1 U/gHb (range: 0.4–6.6 U/g Hb). Aconsiderable number of infantswould not have been identified hadonly a qualitative test been used.18

In the event a qualitative test isused, confirmatory testing maythen be informative. The test weused is superior in that weperformed a quantitative enzymeassay. This method allowsindividuals with levels that arehigher, but still in the G6PD-deficient range, to be detected. In

FIGURE 3Bland-Altman plot in which the solid line is the mean difference between the 2 methods, and thedotted lines represent the 95% confidence interval. Open triangles indicate deficient samples, andsolid triangles indicate normal samples.

FIGURE 4Box plot of G6PD activity comparison. The box represents 75th and 25th percentiles, andthe whiskers represent the minimum and maximum G6PD activity values. Open triangles indicatedeficient samples, and solid triangles indicate normal samples; the yellow dot represents the meanactivity in each case. Assays performed with digital microfluidics (DM) are compared with the assayperformed at the Stanford University Laboratories.

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addition, in those with intermediateG6PD levels, heterozygosity canbe suspected, although the onlydefinitive test for heterozygosity isby using polymerase chain reactionanalysis.

One of the technical limitations of thestudy is that although the assay wasrun at 37°C on the digital microfluidiccartridge, the conventional assay isperformed at room temperature onmost bench studies, including theStanford laboratory. Temperaturedifference is known to affect enzymeactivity. Therefore, all the activityvalues obtained from the digitalmicrofluidic platform were multipliedby 0.559, the factor required tonormalize the activity measured at37°C to that measured at roomtemperature.12 A positive correlationwas found between the 2 platforms.Clearly, both the digital microfluidicmethod as well as the standardlaboratory technique can discriminateG6PD-deficient samples from normalsamples, as has been shown inprevious studies of male neonatalpopulations.19,20 Although there weresome differences in enzyme activityresults between the 2 methods,these discrepancies were minimal,of no clinical significance, and did notaffect the classification of samplestested in the G6PD-deficient ornormal groups.

Preliminary method comparisonresults reported for determiningG6PD activity highlight the potentialfor digital microfluidics to be aneffective G6PD screening tool thatenables fully automated and user-friendly screening for causes leadingto neonatal hyperbilirubinemia. Theonly manual steps are loading ofsample and reagents; all otheroperations, including lysis, reagentpreparation, sample processing,incubation, and waste disposal, werecompletely automated. Eventually, wepropose to test every newborn forbilirubin and G6PD deficiency on thesame cartridge. In a hospital setting,we expect that multiple specimens

can be batched due to the higher dailybirth rate. In other settings withlower number of births, single-samplecartridges can be used. The digitalmicrofluidic system can be used tocontrol both a single-sample cartridgeand a multiple-sample cartridgebecause, fundamentally in digitalmicrofluidics, individual droplets areindependently controlled, allowingunlimited scalability of number ofdroplet operations; thus, cartridgescan be used for single-sample ormultisample testing with the samesoftware-controlled dropletoperations.21 The multiplexedplatform can also providecomprehensive data on neonataljaundice through additional point-of-care screening for total serumbilirubin (results not presented here).In addition, the device has thepotential to include analysis of theUGT1A1 (TA)n promoterpolymorphism (UGT1A1*28)associated with Gilbert syndrome andhyperbilirubinemia in G6PD-deficientneonates.22 The digital microfluidicplatform has also been shown tomultiplex enzymatic assays fornewborn screening for lysosomalstorage disorders in public healthlaboratories using 40 samples ona slightly different cartridge.23,24 Theuse of digital microfluidics for G6PDdeficiency screening has potentialas a point-of-care screening tooleven in the field setting becausethe user is only required to loadsamples and reagents while all othersteps are performed by the cartridgewith no further need for humaninteraction.21

CONCLUSIONS

This study highlights the potentialfor digital microfluidics to be aneffective point-of-care screeningtool for G6PD deficiency, suitableeven in resource-limited settings.Addition of comprehensivebilirubin testing and screening forUGT1A1 gene polymorphismsassociated with neonatal

hyperbilirubinemia could furtherenhance the potential value of thistechnology in pinpointing neonatesat high risk for hyperbilirubinemia.Point-of-care screening is crucial toconditions such ashyperbilirubinemia, wherebya quick treatment response isnecessary and devastating healthconsequences for the newborn canoccur if treatment was delayed dueto wait times for results froma central laboratory.

ACKNOWLEDGMENTS

We acknowledge Dr Sharon Geaghanin the initial phases of this study. Wethank Dr David K. Stevenson for hissupport and the use of his researchlaboratory and Dr Janelle Aby,director of the Well Baby Nursery atLucile Packard Children’s Hospital.We appreciate Dr Glader’s laboratorytechnologist (including CarolynWong) who conducted the goldstandard G6PD assay at the StanfordRed Cell Special Studies Laboratory.The authors specifically thank MartinE. Castillo Cuadrado who recruitedpatients, collected the whole bloodsamples, and conducted theexperiments on the digitalmicrofluidic analyzer; he alsoassisted in the manuscriptpreparation. Ronald J. Wongsupervised the point-of care benchassays performed by Mr CastilloCuadrado; he also provided editorialassistance in the preparation of themanuscript as well expertsupervision to operationalize thistranslational research.

ABBREVIATIONS

G6PD: glucose-6-phosphatedehydrogenase

Hb: hemoglobinNADPH: b-nicotinamide adenine

dinucleotide phosphatehydrate

NADP: b-nicotinamide adeninedinucleotide phosphate

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Address correspondence to Vinod K. Bhutani, MD, Department of Pediatrics, Division of Neonatal and Developmental Medicine, Stanford University, 750 Welch Rd,

#315, Palo Alto, CA 94304. E-mail: bhutani@stanford.edu

PEDIATRICS (ISSN Numbers: Print, 0031-4005; Online, 1098-4275).

Copyright © 2015 by the American Academy of Pediatrics

FINANCIAL DISCLOSURE: Dr Kleinert was an employee of Advanced Liquid Logic, Inc, and Dr Pamula is an employee of Baebies, Inc, and has stock ownership. The

other authors have indicated they have no financial relationships relevant to this article to disclose.

FUNDING: Research reported in this publication was supported by the Eunice Kennedy Shriver National Institute of Child Health and Human Development of the

National Institutes of Health under award number R44HD062316. All phases of this study were supported by National Institutes of Health grant R44HD062316. Funded

by the National Institutes of Health (NIH).

POTENTIAL CONFLICT OF INTEREST: Dr Kleinert was an employee of Advanced Liquid Logic, Inc at the time of the study and is now an employee at Illumina, Inc which

acquired Advanced Liquid Logic, Inc, and Dr Pamula is an employee of Baebies, Inc, and has stock ownership. The other authors have indicated they have no

potential conflicts of interest to disclose.

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DOI: 10.1542/peds.2015-2122 originally published online October 12, 2015; 2015;136;e1268Pediatrics 

Vamsee PamulaVinod K. Bhutani, Michael Kaplan, Bertil Glader, Michael Cotten, Jairus Kleinert and

Enzyme DeficiencyPoint-of-Care Quantitative Measure of Glucose-6-Phosphate Dehydrogenase

ServicesUpdated Information &

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Referenceshttp://pediatrics.aappublications.org/content/136/5/e1268#BIBLThis article cites 23 articles, 9 of which you can access for free at:

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DOI: 10.1542/peds.2015-2122 originally published online October 12, 2015; 2015;136;e1268Pediatrics 

Vamsee PamulaVinod K. Bhutani, Michael Kaplan, Bertil Glader, Michael Cotten, Jairus Kleinert and

Enzyme DeficiencyPoint-of-Care Quantitative Measure of Glucose-6-Phosphate Dehydrogenase

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ISSN: 1073-0397. 60007. Copyright © 2015 by the American Academy of Pediatrics. All rights reserved. Print the American Academy of Pediatrics, 141 Northwest Point Boulevard, Elk Grove Village, Illinois,has been published continuously since 1948. Pediatrics is owned, published, and trademarked by Pediatrics is the official journal of the American Academy of Pediatrics. A monthly publication, it

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