Body surface area

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 true glomerular filtration rate (GFR);
• The Quetelet index uses a somewhat modified form of the BSA.
• The cardiac index is a measure of cardiac 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, where Body 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, M is the subject's mass, and H is the subject's height.

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 the Body mass index fails to do.^[6]

${\displaystyle {BSA}=a\times M^{0.425}\times H^{0.725}}$

where ${\displaystyle a=71.84{cm}^{1.275}{kg}^{-0.425}}$

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

${\displaystyle {BSA}=b{\sqrt {M\times H}}}$

where ${\displaystyle b={\frac {1000}{6}}{cm}^{1.5}{kg}^{-0.5}}$, or:

${\displaystyle {BSA}={\sqrt {\frac {{\mbox{height}}\times {\mbox{weight}}}{3600}}}}$

Other formulas for BSA include:

Haycock[8]	${\displaystyle c\times M^{0.5378}\times H^{0.3964}}$
Gehan and George[9]	${\displaystyle d\times M^{0.51456}\times H^{0.42246}}$
Boyd [10]	${\displaystyle e\times ({\frac {M}{1kg}})^{0.0188log_{10}{\frac {f}{M}}}\times H^{0.3}}$
Fujimoto[11]	${\displaystyle g\times M^{0.444}\times H^{0.663}}$
Takahira[11]	${\displaystyle h\times M^{0.425}\times H^{0.725}}$
Shuter and Aslani[12]	${\displaystyle i\times M^{0.441}\times H^{0.655}}$
Lipscombe [13]	${\displaystyle j\times M^{0.434972}\times H^{0.67844}}$
Schlich[14]	${\displaystyle k\times M^{0.46}\times H^{1.08}}$       (women)
	${\displaystyle l\times M^{0.38}\times H^{1.24}}$       (men)

where ${\displaystyle c=242.65{cm}^{1.6036}{kg}^{-0.5378}}$, ${\displaystyle d=235{cm}^{1.57754}kg^{-0.51456}}$, ${\displaystyle e=333{cm}^{1.7}}$, ${\displaystyle f=10^{\frac {0.6157}{0.0188}}kg}$, ${\displaystyle g=88.83{cm}^{1.337}{kg}^{0.556}}$, ${\displaystyle h=72.41{cm}^{1.275}{kg}^{-0.425}}$, ${\displaystyle i=94.9{cm}^{1.345}{kg}^{-0.441}}$, ${\displaystyle j=87.8108{cm}^{1.32156}{kg}^{-0.434972}}$, ${\displaystyle k=9.75482{cm}^{0.96}{kg}^{-0.46}}$, and ${\displaystyle l=5.79479{cm}^{0.76}{kg}^{-0.38}}$.

For any formula, the units should match. Lipscombe, following Mosteller's reasoning, observed that the formulas obtained by Fujimoto, Shuter and Aslani, Takahira, and Lipscombe are suggestive of ${\displaystyle m\times M^{4/9}\times H^{2/3}}$, where the coefficient m's numerical value is solely dependent on the density unit, specifically equal to ${\displaystyle {\frac {800}{9}}({\frac {kg}{{cm}^{3}}})^{-{\frac {4}{9}}}}$.

A weight-based formula that does not include a square root (making it easier to use) was proposed by Costeff and recently validated for the pediatric age group. It is ${\displaystyle n{\frac {4M+o}{M+p}}}$, where ${\displaystyle n=1m^{2}}$, ${\displaystyle o=7kg}$, and ${\displaystyle p=90kg}$.^[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 of 1.73 m² for 3,000 cancer patients from 1990 to 1998 in a European Organisation for Research and Treatment of Cancer (EORTC) database.^[19]

During 2005 there was an average BSA of 1.79 m² for 3,613 adult cancer patients in the UK. Among them, the average BSA for men was 1.91 m² and for women was 1.71 m².^[20]

• Total body surface area