Inphysiology andmedicine, thebody surface area (BSA) is the measured or calculatedsurface area of ahuman body. For many clinical purposes, BSA is a better indicator of metabolic mass thanbody 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 narrowtherapeutic index, such aschemotherapy.

Typically there is a 4–10 fold variation indrug clearance between individuals due to differing the activity ofdrug elimination processes related to genetic and environmental factors. This can lead to significant overdosing and underdosing (and increased risk of disease recurrence). It is also thought to be a distorting factor inPhase I and II trials that may result in potentially helpful medications being prematurely rejected.^[1][2] The trend topersonalized medicine is one approach to counter this weakness.

Examples of uses of the BSA:

• Renal clearance usually divided by the BSA i.e. per 1.73 m² to gain an appreciation of the trueglomerular filtration rate (GFR);
• TheQuetelet index uses a somewhat modified form of the BSA;
• Thecardiac index is a measure ofcardiac output divided by the BSA, giving a better approximation of the effective cardiac output;
• Chemotherapy is often dosed according to the patient's BSA.
• Glucocorticoid dosing is also expressed in terms of BSA for calculating maintenance doses or to compare high dose use with maintenance requirement.

There is some evidence that BSA values are less accurate at extremes of height and weight, whereBody Mass Index may be a better estimate (for hemodynamic parameters).^[3]

Various calculations have been published to arrive at the BSA without direct measurement. In the following formulae, BSA is expressed inm², weight (or, more properly, mass) W inkg, and height H incm.

The most widely used is the Du Bois formula,^[4][5] which has been shown to be equally as effective in estimating body fat in obese and non-obese patients, something theBody mass index fails to do.^[6]

${\displaystyle BSA=0.007184\times W^{0.425}\times H^{0.725}}$

The Mosteller formula is also commonly used, and is mathematically simpler:^[7]

${\displaystyle BSA=\frac{\sqrt{W\times H}}{60}=0.016667\times W^{0.5}\times H^{0.5}}$

Other formulas for BSA in m² include:

Haycock[8]	${\displaystyle 0.024265\times W^{0.5378}\times H^{0.3964}}$
Gehan and George[9]	${\displaystyle 0.0235\times W^{0.51456}\times H^{0.42246}}$
Boyd[10]	${\displaystyle 0.03330\times W^{(0.6157-0.0188{\log }_{10}W)}\times H^{0.3}}$
or alternatively	${\displaystyle 0.0003207\times \mathrm{w}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}{(\mathrm{g})}^{(0.7285-0.0188{\log }_{10}\mathrm{w}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}(\mathrm{g}))}\times H^{0.3}}$
Fujimoto[11]	${\displaystyle 0.008883\times W^{0.444}\times H^{0.663}}$
Takahira[11]	${\displaystyle 0.007241\times W^{0.425}\times H^{0.725}}$
Shuter and Aslani[12]	${\displaystyle 0.00949\times W^{0.441}\times H^{0.655}}$
Lipscombe[13]	${\displaystyle 0.00878108\times W^{0.434972}\times H^{0.67844}}$
Schlich[14]	${\displaystyle 0.000975482\times W^{0.46}\times H^{1.08}}$       (women)
	${\displaystyle 0.000579479\times W^{0.38}\times H^{1.24}}$       (men)

For any formula, the units should match. Mosteller pointed out that his formula holds only if the density is treated as a constant for all humans. Lipscombe, following Mosteller's reasoning, observed that the formulas obtained by Fujimoto, Shuter and Aslani, Takahira, and Lipscombe are suggestive of${\displaystyle 8/900\times W^{4/9}\times H^{2/3}}$, which is dimensionally correct for the case of constant density. It equals${\displaystyle (2^3/3^2)\times (W^{2/3}H{)}^{2/3}/100}$.

A weight-based formula that does not include a square root (making it easier to use) was proposed byCosteff and recently validated for the pediatric age group. It is [4W (kg) + 7]/[90 + W (kg)].^[15][16]

Average BSA for children of various ages, for men, and for women, can be estimated using statistical survey data and a BSA formula:^[17]

The estimations in the above tables are based weight and height data from the U.S. NCHS National Health and Nutrition Examination Survey (2011-2014).^[18]

There was an average BSA of1.73 m² for 3,000 cancer patients from 1990 to 1998 in aEuropean Organisation for Research and Treatment of Cancer (EORTC) database.^[19]

During 2005 there was an average BSA of1.79 m² for 3,613 adult cancer patients in the UK. Among them the average BSA for men was1.91 m² and for women was1.71 m².^[20]

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