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Neck Circumference as a Screening Measure for Identifying Children With High Body Mass Index Olubukola O. Nafiu, Constance Burke, Joyce Lee, Terri Voepel-Lewis, Shobha Malviya and Kevin K. Tremper Pediatrics 2010;126;e306; originally published online July 5, 2010; DOI: 10.1542/peds.2010-0242 The online version of this article, along with updated information and services, is located on the World Wide Web at: http://pediatrics.aappublications.org/content/126/2/e306.full.html PEDIATRICS is the of
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  DOI: 10.1542/peds.2010-0242; srcinally published online July 5, 2010;2010;126;e306 Pediatrics Malviya and Kevin K. TremperOlubukola O. Nafiu, Constance Burke, Joyce Lee, Terri Voepel-Lewis, Shobha Body Mass IndexNeck Circumference as a Screening Measure for Identifying Children With High    http://pediatrics.aappublications.org/content/126/2/e306.full.html located on the World Wide Web at:The online version of this article, along with updated information and services, is  of Pediatrics. All rights reserved. Print ISSN: 0031-4005. Online ISSN: 1098-4275.Boulevard, Elk Grove Village, Illinois, 60007. Copyright © 2010 by the American Academypublished, and trademarked by the American Academy of Pediatrics, 141 Northwest Pointpublication, it has been published continuously since 1948. PEDIATRICS is owned,PEDIATRICS is the official journal of the American Academy of Pediatrics. A monthly  by guest on March 7, 2012pediatrics.aappublications.orgDownloaded from   Neck Circumference as a Screening Measure forIdentifying Children With High Body Mass Index WHAT’S KNOWN ON THIS SUBJECT: BMI is a poor descriptor of central adiposity, a well-described risk factor for poorcardiometabolic phenotype. Other surrogates of body fatness arebeing investigated. WHAT THIS STUDY ADDS: The authors provide data on theusefulness of neck circumference measurements for identifyingchildren with high BMI. They provide age- and gender-specificneck circumference cut points for identifying children who areoverweight or obese. abstract OBJECTIVES: Overweight in children is most commonly described byusing BMI. Because BMI does not adequately describe regional (cen- tral) adiposity, other indices of body fatness are being explored. Neckcircumference (NC) is positively associated with obstructive sleep ap-nea, diabetes, and hypertension in adults. NC also has positive corre-lation with BMI in adults. The possible role of NC in screening for highBMI in children is not well characterized. The aims of this investigationweretoexaminethecorrelationbetweenBMIandNCinchildrenandtodetermine the best NC cutoff that identifies children with high BMI. METHODS: Children who were aged 6 to 18 years and undergoing elec- tive noncardiac surgeries were the subjects of this study. Trained re-search assistants collected clinical and anthropometric data from allpatients. We calculated Pearson correlation coefficients between NCandotherindicesofobesity.Wethendeterminedbyreceiveroperatingcharacteristic analyses the optimal NC cutoff for identifying childrenwith high BMI. RESULTS: Among 1102 children, 52% were male. NC was significantlycorrelated with age, BMI, and waist circumference in both boys andgirls, although the correlation was stronger in older children. OptimalNC cutoff indicative of high BMI in boys ranged from 28.5 to 39.0 cm.Corresponding values in girls ranged from 27.0 to 34.6 cm. CONCLUSIONS: NC is significantly correlated with indices of adiposityand can reliably identify children with high BMI. NC is a simple tech-nique that has good interrater reliability and could be used to screenfor overweight and obesity in children. Pediatrics 2010;126:e306–e310 AUTHORS: Olubukola O. Nafiu, MD, a Constance Burke,BSN, a Joyce Lee, MD, MPH, b Terri Voepel-Lewis, MSN, a Shobha Malviya, MD, a and Kevin K. Tremper, MD a Departments of  a  Anesthesiology and  b Pediatric Endocrinology,University of Michigan, Ann Arbor, Michigan KEY WORDS neck circumference, childhood obesity, body mass index, centraladiposity ABBREVIATIONS WC—waist circumferenceNC—neck circumferenceROC—receiver operating characteristicAUC—area under the curveLR  —positive likelihood ratioLR  —negative likelihood ratiowww.pediatrics.org/cgi/doi/10.1542/peds.2010-0242doi:10.1542/peds.2010-0242Accepted for publication Apr 8, 2010Address correspondence to Olubukola O. Nafiu, MD, 1500 EMedical Centre Dr, University of Michigan Health System, RoomUH 1H247, Ann Arbor, MI 48109-0048. E-mail:onafiu@med.umich.eduPEDIATRICS (ISSN Numbers: Print, 0031-4005; Online, 1098-4275).Copyright © 2010 by the American Academy of Pediatrics FINANCIAL DISCLOSURE: The authors have indicated they have no financial relationships relevant to this article to disclose. e306 NAFIU et al  by guest on March 7, 2012pediatrics.aappublications.orgDownloaded from   Childhood overweight and obesity re-mains a worldwide public health con-cern. 1 The most widely used tool fordefining overweight and obesity inboth adults and children is BMI, whichis defined as an individual’s weight inkilograms divided by the square of  their height in meters (BMI  kg/m 2 ). 2 Despite the ease of use and popularityof BMI as an anthropometric tool, it isbecoming increasingly clear that it isnot a good proxy for regional adipos-ity. 3 Regional deposition of fat, espe-cially in the upper body segment, is abetter predictor of some obesity-related complications, such as hyper- tension, diabetes, and heart disease. 4 Many studies have demonstrated thevalue of waist circumference (WC) asan index of central obesity. 5,6 Other in-vestigatorshaveshownthatWC,eithersingly or in combination with BMI, mayhave a stronger relation to somehealth outcomes than BMI alone. 7,8 Neck circumference (NC) has alsobeen used as a potential proxy for obe-sity and cardiovascular disease inadults. 9,10 Veryfewinvestigators 11 haveattempted to use NC to screen for highBMI in children; therefore, the objec- tives of this study were to examine thecorrelation between NC and BMI inchildren,toexaminetheabilityofNCtoidentify correctly children with highBMI, and to determine the best NC cutpointforidentifyingchildrenofvariousagesasoverweight/obese.Ourapriorihypothesis was that a significant pro-portion of children with high NC wouldalso be overweight or obese. METHODS After institutional review board ap-proval, we prospectively recruited1102 children who were aged 6 to 18yearsandundergoingelective,noncar-diac surgical procedures at the MottChildren’s Hospital, University of Mich-igan, for inclusion in this study. Wechose a lower cutoff age of 6 years be-cause of increased difficulty withcompliance while measuring anthro-pometric parameters in younger chil-dren. In addition, previous investiga- tors 12 showed that landmarking ismore difficult in children who areyounger than 5, leading to poor inter-rater and intrarater reliability of NCmeasurements.Childrenwithgoiterorother neck masses, neck deformity, or tracheostomy or cervical collar wereexcluded from this study. Measurements Trained research assistants took allclinical and anthropometric measure-ments. Height was measured to thenearest 0.1 cm by using a wall-mounted stadiometer with the pa- tientsshoelessandheadheldinFrank-furt horizontal plane. Body weight wasmeasured, to the nearest 0.1 kg, by us-ing a calibrated electronic weighingscale with patients lightly clad in hos-pital gowns. NC was measured by us-ing a flexible tape, with the children in the standing position, head held erect,at the level of the thyroid cartilage. WCwas measured (to the nearest 0.1 cm)with the children standing, at the endof normal expiration, by using an in-elastictapeatapointmidwaybetween the inferior margin of the lowest riband the iliac crest. Measurementswere obtained with the tape snug butnot compressing the skin. BMI was cal-culated for all patients and was con-verted to age- and gender-specific per-centiles according to the 2000 Centersfor Disease Control and Preventiongrowth curves. 13 Operational Definition of Terms Children with a BMI  85th percentilewere classified as having normalweight, whereas children with BMI  85th percentile were classified asbeing overweight/obese. 13 We alsostratified children into 2 age groups:young children (age  10 years) andolder children (age  10 years). Statistical Analysis Data analyses were performed withSPSS 17.0 for Windows and MedCalc7.4.1.1 (written by Frank Schoonjans,Mariakerke, Belgium). Means and SDsof age and anthropometric variableswere compared along gender lines.Pearson correlation coefficient wasused to explore the association be- tween NC and other continuous vari-ables, such as age, WC, BMI, and base-line blood pressure.Receiver operating characteristic(ROC) analyses 14 were used to deter-mine the predictive validity of NC aswell as evaluate optimal cutoff valuesfor identifying overweight or obesechildren. ROC curves determine thediscriminatory power of a screeningmeasure for correctly identifying indi-viduals on the basis of their classifica- tion by a reference test. The ROC curveis a plot of true-positive rate (sensitiv-ity) against the false-positive rate (1  specificity). A good test will have itsROCcurveskewedtotheupperleftcor-ner. 15 The area under the curve (AUC)describes the probability that a testwill correctly identify a pair of patientswho do and do not have a disease andwere randomly selected from a popu-lation; a perfect score will have an AUCof 1, whereas an AUC of 0.5 means that the test performs no better thanchance. For this study, patients with true-positive results were those withhigh BMI and high NC. Patientswith false-positive results were thosewithhighNCandlowBMI.Patientswithfalse-negative results were those withlow NC and high BMI. Sensitivity wascalculated as true-positive results/(true-positive results  false-negativeresults); specificity was calculated as true-negative results/(true-negativeresults  false-positive results). Cut-off values and the corresponding AUCas well as the likelihood ratios (posi- tive [LR  ] and negative [LR  ]) for NC that were predictive of overweight/ ARTICLES PEDIATRICS Volume 126, Number 2, August 2010 e307  by guest on March 7, 2012pediatrics.aappublications.orgDownloaded from   obesity were computed along age andgenderlines.TheLR  ofapositivetestresult is sensitivity divided by 1  specificity and indicates how much theodds of a disease increase when a testis positive. Conversely, the LR  indi-cates 1  sensitivity divided by speci-ficityandindicateshowmuchtheoddsof a disease decrease when a test isnegative. RESULTS Atotalof1102childrenmetthecriteriafor inclusion in this study; the majority(70.6%)underwentoutpatientsurgery.The distribution of surgical specialtieswere as follows: orthopedics, 22.6%;urology, 12.7%; general surgery,13.8%; otorhinolaryngology, 19.4%;ophthalmology, 6.7%; and others,24.8%. The mean age of patients in thisseries was 10.7  3.6 years. The meanNC in young boys with normal BMI wassignificantly greater than for younggirls with normal BMI (28.1  1.9 vs26.9  2.0 cm; P   .001). Similarly, NCin overweight/obese young boys was  2 cm greater than for young girls of comparable BMI category (31.2  4.4vs 29.9  3.0 cm; P   .001). Table 1details the remaining baseline charac- teristics of the study population strat-ified according to age group, BMI cate-gory, and gender. As expected, all of  the anthropometric parameters weresignificantly higher in overweight/obese children than in their normalweight peers. Similarly, baseline sys- tolic blood pressure was significantlyhigher in overweight/obese children than their lean peers in both youngand older children.Table 2 presents the Pearson correla- tion coefficients between NC and someclinical and anthropometric parame- ters for boys and girls. NC showed astrong positive correlation with age,BMI, WC, and height and weight in bothboys and girls. In addition, NC was pos-itively correlated with blood pressurein both genders. There was a strongpositive correlation between all of theanthropometric parameters in bothyoung and older children, although thecorrelation coefficients were higher inolderchildren(Table3).Inaddition,NCseemstocorrelatebetterwithBMIandWC in boys than in girls. Similarly, there was a closer correlation be- tween NC and the other anthropomet-ric indices in older than in youngerchildren (Table 3).Table 4 shows the AUC for each 1-yearage group including the optimal NCcutoffs and the corresponding sensi- tivities and specificities for classifyingchildren into high BMI groups in boys.The likelihood ratios for each cutoff points are also shown. For example,LR  fora6-year-oldboywithNC  28.5cm indicates that he is 3.6 times morelikely to be overweight or obese than a6-year-old boy with NC values below TABLE 1 Baseline Characteristics of the Children According to Age Group, BMI Category, andGender Variable Young Children (Age  10 y) Older Children (Age  10 y)Normal BMI( n  404)High BMI( n  248) P  Normal BMI( n  282)High BMI( n  168) P  BoysAge, y 7.7  1.5 7.6  1.4 .510 14.0  2.1 13.7  1.9 .236Weight, kg 26.6  9.3 37.6  13.2  .001 51.4  12.2 77.6  21.4  .001Height, cm 127.0  14.4 130.7  14.2 .029 163.2  13.7 164.4  12.9 .199BMI, kg/m 2 16.4  1.4 23.1  4.7  .001 19.1  2.4 28.9  5.8  .001WC, cm 59.1  6.3 73.7  15.0  .001 73.4  8.6 96.9  14.6  .001NC, cm 28.1  1.9 31.2  4.4  .001 33.1  3.1 37.6  4.1  .001SBP, mm Hg 101.3  14.2 108.4  14.2  .001 115.2  13.0 118.7  14.8  .041DBP, mm Hg 60.9  8.3 63.4  9.3 .022 64.9  9.3 66.5  8.7 .172GirlsAge, y 7.8  1.4 7.7  1.4 .967 14.3  2.1 13.7  2.1 .050Weight, kg 25.5  6.3 36.9  13.4  .001 48.9  10.6 69.3  17.7  .001Height, cm 126.9  11.8 130.0  13.9 .062 156.1  13.5 158.6  11.0 .118BMI, kg/m 2 15.7  1.6 22.8  4.4  .001 19.4  2.6 28.4  5.7  .001WC, cm 58.2  6.0 73.3  13.4  .001 72.2  8.0 93.3  15.8  .001NC, cm 26.9  2.0 29.9  3.0  .001 30.9  2.3 34.3  3.5  .001SBP, mm Hg 103.0  11.9 109.0  14.2  .001 110.7  12.7 118.0  11.7  .001DBP, mm Hg 61.7  8.3 63.8  8.1 .055 65.7  8.8 67.9  9.6 .078 SBP indicates systolic blood pressure; DBP, diastolic blood pressure. TABLE 2 Relationship Between NC and OtherAnthropometric Variables by Gender Variable NC, cmBoys Girls r P r P  Age 0.66  .001 0.61  .001Weight 0.81  .001 0.84  .001Height 0.66  .001 0.63  .001BMI 0.71  .001 0.78  .001WC, cm 0.77  .001 0.83  .001 TABLE 3 Pearson Correlation Coefficients of  the Anthropometric Indices by Ageand Gender Age, y BMI-WC BMI-NC WC-NC P  Boys6 0.77 0.59 0.59  .0017 0.76 0.57 0.57  .0018 0.84 0.66 0.69  .0019 0.89 0.83 0.85  .00110 0.88 0.73 0.74  .00111 0.71 0.68 0.68  .00112 0.89 0.75 0.73  .00113 0.92 0.67 0.65  .00114 0.84 0.74 0.76  .00115 0.89 0.76 0.75  .00116 0.92 0.74 0.82  .00117 0.94 0.84 0.86  .00118 0.88 0.87 0.86  .001Girls6 0.57 0.47 0.50  .0017 0.86 0.82 0.82  .0018 0.86 0.87 0.83  .0019 0.78 0.76 0.64  .00110 0.84 0.82 0.74  .00111 0.94 0.88 0.7  .00112 0.85 0.75 0.77  .00113 0.88 0.72 0.68  .00114 0.88 0.58 0.62  .00115 0.91 0.56 0.65  .00116 0.94 0.74 0.71  .00117 0.91 0.81 0.85  .00118 0.83 0.70 0.74  .001 e308 NAFIU et al  by guest on March 7, 2012pediatrics.aappublications.orgDownloaded from 
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