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| In [[physiology]] and [[medicine]], the '''body surface area''' (BSA) is the measured or calculated [[surface area]] of a [[human body]]. For many clinical purposes BSA is a better indicator of metabolic mass than body weight because it is less affected by abnormal adipose mass. Nevertheless, there have been several important critiques of the use of BSA in determining the dosage of medications with a narrow [[therapeutic index]] like many chemotherapy medications. Typically there is a 4-10 fold variation in cytotoxic drug clearance between individuals due to differing activity of drug elimination processes related to genetic and environmental factors. This can lead to significant overdosing and even more perniciously to underdosing (and increased risk of cancer recurrence). It is also thought to be a distorting factor in Phase I and II trials that may result in potentially helpful medications being prematurely rejected.<ref>{{cite journal |author=Gurney H |title=How to calculate the dose of chemotherapy |journal=Br. J. Cancer |volume=86 |issue=8 |pages=1297–302 |date=April 2002 |pmid=11953888 |pmc=2375356 |doi=10.1038/sj.bjc.6600139 |url=http://www.nature.com/bjc/journal/v86/n8/full/6600139a.html}}</ref><ref>{{cite journal |author=Gao B, Klumpen HJ, Gurney H |title=Dose calculation of anticancer drugs |journal=Expert Opin Drug Metab Toxicol |volume=4 |issue=10 |pages=1307–19 |date=October 2008 |pmid=18798700 |doi=10.1517/17425255.4.10.1307}}</ref> The trend to [[personalized medicine]] is one approach to counter this weakness. Estimation of BSA is simpler than many measures of volume.
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| ==Uses==
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| Examples of uses of the BSA:
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| * [[Renal function|Renal clearance]] is usually divided by the BSA to gain an appreciation of the true required [[glomerular filtration rate]] (GFR);
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| * The [[Quetelet index]] uses a somewhat modified form of the BSA;
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| * The [[cardiac index]] is a measure of [[cardiac output]] divided by the BSA, giving a better approximation of the required cardiac output;
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| * [[Chemotherapy]] is often dosed according to the patient's BSA.
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| * [[Glucocorticoid]] dosing is also expressed in terms of BSA for calculating maintenance doses or to compare high dose use with maintenance requirement.
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| ==Calculation==
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| Various calculations have been published to arrive at the BSA without direct measurement. In the following formulas, BSA is in [[meter|m]]<sup>2</sup>, W is weight in [[kilogram|kg]], and H is height in [[centimeter|cm]].
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| The most widely used is the Du Bois formula:<ref name='Du Bois1916'>{{cite journal | title = A formula to estimate the approximate surface area if height and weight be known | journal = Archives of Internal Medicine | date = Jun 1916 | authors= Du Bois D, Du Bois EF | volume = 17 | issue = 6 | pages = 863–71 | id = | url = http://cel.webofknowledge.com/InboundService.do?SID=3CeciDMOG31LDnPHlmd&product=CEL&UT=000202580600002&SrcApp=Highwire&Init=Yes&action=retrieve&Func=Frame&customersID=Highwire&SrcAuth=Highwire&IsProductCode=Yes&mode=FullRecord | accessdate = 2012-09-09 | pmid=2520314}}</ref><ref name='Verbraecken2006'>{{cite journal | title = Body surface area in normal-weight, overweight, and obese adults. A comparison study | journal = Metabolism — Clinical and Experimental | date = Apr 2006 | first = J | last = Verbraecken | coauthors = Van de Heyning P, De Backer W, Van Gaal L | volume = 55 | issue = 4 | pages = 515–24 | id = | doi = 10.1016/j.metabol.2005.11.004 | url = http://www.metabolismjournal.com/article/S0026-0495(05)00437-3/abstract | accessdate = 2012-09-07 | pmid=16546483}}</ref>
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| :<math>{BSA}=0.007184 \times W^{0.425} \times H^{0.725} </math>
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| A commonly used and simple one is the Mosteller formula:<ref>Mosteller RD. "Simplified calculation of body-surface area". [[N Engl J Med]] 1987; 317:1098. PMID 3657876.</ref>
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| :<math>{BSA }= \sqrt\frac{W \times H }{3600}
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| = 0.016667 \times W^{0.5} \times H^{0.5} </math> or even simpler :<math>{BSA}= \sqrt{W \times H} / {60} </math> or if Ht is height in [[meter|m]] :<math>{BSA}= \sqrt{W \times Ht} / {6} </math>
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| Other formulas for BSA in m<sup>2</sup> include:
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| :{|
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| | Haycock<ref>Haycock GB, Schwartz GJ, Wisotsky DH "Geometric method for measuring body surface area: A height-weight formula validated in infants, children and adults" ''J Pediatr'' 1978, 93:62-66.</ref> || <math> 0.024265 \times W^{0.5378} \times H^{0.3964}</math>
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| |Gehan and George<ref>Gehan EA, George SL, ''Cancer Chemother Rep'' 1970, 54:225-235</ref> || <math> 0.0235 \times W^{0.51456} \times H^{0.42246} </math>
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| |Boyd <ref name='Current1998'>{{cite journal | title = A Linear Equation For Estimating The Body Surface Area In Infants And Children | journal = The Internet Journal of Anesthesiology | year = 1998 | first = JD | last = Current | volume = 2 | issue = 2 | doi = 10.5580/1c6c | url = http://www.ispub.com/journal/the-internet-journal-of-anesthesiology/volume-2-number-2/a-linear-equation-for-estimating-the-body-surface-area-in-infants-and-children.html | accessdate = 2012-09-09}}</ref><ref name='Boyd1935'>Boyd, Edith (1935). ''The Growth of the Surface Area of the Human Body.'' University of Minnesota. The Institute of Child Welfare, Monograph Series, No. x. London: Oxford University Press.</ref> || <math> 0.0003207
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| \times weight \mbox{(g)}^{(0.7285 - 0.0188 \log_{10}{weight \mathrm{ (g)}})}
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| \times H^{0.3} </math>
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| | or equivalently || <math> 0.03330
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| \times W^{(0.6157 - 0.0188 \log_{10} {W})} \times H^{0.3} </math>
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| |Fujimoto<ref name='Fujimoto1968'>Fujimoto S, Watanabe T, Sakamoto A, Yukawa K, Morimoto K. Studies on the physical surface area of Japanese. 18. Calculation formulae in three stages over all ages. Nippon Eiseigaku Zasshi 1968;5:443–50.</ref> || <math> 0.008883 \times W^{0.444} \times H^{0.663} </math>
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| |Takahira<ref name='Fujimoto1968' /> || <math> 0.007241 \times W^{0.425} \times H^{0.725} </math>
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| |rowspan=2 | Schlich<ref name=Schlich>Schlich E, Schumm M, Schlich M: "3-D-Body-Scan als anthropometrisches Verfahren zur Bestimmung der spezifischen Körperoberfläche". [[Ernährungs Umschau]] 2010;57:178-183.</ref> || <math>0.000975482 \times W^{0.46} \times H^{1.08} </math> (women)
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| |<math>0.000579479 \times W^{0.38} \times H^{1.24} </math> (men)
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| |}
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| A weight-based formula was proposed by Costeff and recently validated for the pediatric age group that does not include a square root, making it easier to use. It is [4Wkg+7]/[90+Wkg].<ref>Costeff H, "A simple empirical formula for calculating approximate surface area in children.," ''Arch Dis Child'', vol. 41, no. 220, pp. 681–683, Dec. 1966.</ref><ref name=Furqan>{{cite journal|last=Furqan|first=M|coauthors=Haque, A|title=Surface area in children: a simple formula.|journal=Indian pediatrics|date=December 2009|year=2009|volume=46|issue=12|pages=1085–7|pmid=19430073}}</ref>
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| ==Average values==
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| Average BSA for children of various ages, for men, and for women, are taken to be:
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| :{|
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| | colspan=3 | Neonate (newborn) || 0.25 ||m²
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| | colspan=2 | Child of 2 years || || 0.5 || m²
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| | colspan=2 align="right" | 9 years ||   || 1.07 || m²
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| | colspan=2 align="right" | 10 years || || 1.14 || m²
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| | colspan=2 align="right" | 12–13 years || || 1.33 || m²
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| | colspan=3 | Women || 1.6 || m²
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| |colspan=3 | Men || 1.9 || m²
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| |}
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| There was an average BSA of {{nowrap|1.73 m<sup>2</sup>}} for 3,000 cancer patients from 1990 to 1998 in a [[European Organisation for Research and Treatment of Cancer]] (EORTC) database.<ref name='Sparreboom2003'>{{cite journal | title = Paclitaxel Pharmacokinetics, Threshold Models, and Dosing Strategies | journal = Journal of Clinical Oncology | date = 15 Jul 2003 | authors = Sparreboom A, Verweij J | volume = 21 | issue = 14 | pages = 2803–4 | id = | doi = 10.1200/JCO.2003.99.038 | url = http://jco.ascopubs.org/content/21/14/2803.full | accessdate = 2012-09-09 | pmid=12860961}}</ref> During 2005 there was an average BSA of {{nowrap|1.79 m<sup>2</sup>}} for 3,613 adult cancer patients in the UK. Among them the average BSA for men was {{nowrap|1.91 m<sup>2</sup>}} and for women was {{nowrap|1.71 m<sup>2</sup>}}.<ref name='Sacco2010'>{{cite journal | title = The Average Body Surface Area of Adult Cancer Patients in the UK: A Multicentre Retrospective Study | journal = [[PLoS One]] | date = 28 Jan 2010 | authors = Sacco JJ, Botten J, Macbeth F, Bagust A, Clark P | volume = 5 | issue = 1 | page = e8933 | id = | doi = 10.1371/journal.pone.0008933 | url = http://ukpmc.ac.uk/articles/PMC2812484/reload=0;jsessionid=VMxGfFGKF2er3zi0XF6N.4 | accessdate = 2012-09-09 | pmid=20126669}}</ref>
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| ==References==
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| {{Reflist}}
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| ==External links==
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| * [http://www.miniwebtool.com/bsa-calculator/ Online BSA Calculator] Calculate body surface area using any of five formulas.
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| * [http://www.bccancer.bc.ca/HPI/drugdatabase/appendices/appendix9.htm BC Cancer network] BSA calculation guidelines.
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| * [http://www.cato.eu/body-surface-area.html Online Body Surface Area Calculator (Dubois Formula)]
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| * [http://www.cato.eu/body-surface-area-children-1.html Online Body Surface Area Calculator (Mosteller Formula)]
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| * [http://www.webcooltools.com/Medicine/BSA.html Web CoolTool to Calculate BSA using any of the five formulae]
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| [[Category:Pharmacology]]
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