Body surface area

In physiology and medicine, the body surface area (BSA) is the measured or calculated surface 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. Estimation of BSA is simpler than many measures of volume.

Uses

Examples of uses of the BSA:
* Renal function is usually fractioned over the BSA to gain an appreciation of the true required 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 required 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.

Calculation

Various calculations have been published to arrive at the BSA without direct measurement, starting in 1916 with the Dubois & Dubois formula [Du Bois & Du Bois,"Arch Intern Med" 1916, 17:863] :

:$\{BSA\}=(0.007184\; imes\; \{weight\; mbox\{\; (kg)^\{0.425\}\; imes\; \{height\; mbox\{\; (cm)^\{0.725\})$

One commonly used formula is the Mosteller formula, published in 1987 [Mosteller RD. "Simplified calculation of body-surface area". N Engl J Med 1987; 317:1098. PMID 3657876.] and adopted for use by the Pharmacy and Therapeutics Committee of the Cross Cancer Institute, Edmonton, Alberta, Canada:

:$\{BSA\}=\; sqrtfrac\{weight\; mbox\{\; (kg)\}\; imes\; height\; mbox\{\; (cm)\}\; \}\{3600\}$

Other formulas include the Haycock formula [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.] ::$\{BSA\}=0.024265\; imes\; \{weight\; mbox\{\; (kg)^\{0.5378\}\; imes\; \{height\; mbox\{\; (cm)^\{0.3964\}$

the Gehan and George formula [Gehan EA, George SL, "Cancer Chemother Rep" 1970, 54:225-235] ::$\{BSA\}\; =\; 0.0235\; imes\; weight\; mbox\{\; (kg)\}^\{0.51456\}\; imes\; height\; mbox\{\; (cm)\}^\{0.42246\}$

the Boyd formula [http://www.ispub.com/journals/IJA/Vol2N2/bsa.htm (from Boyd E, The growth of the surface area of the human body. Minneapolis: University of Minnesota Press, 1935.)] ::$\{BSA\}\; =\; 0.0003207\; imes\; weight\; mbox\{\; (g)\}^\{(0.7285\; -\; 0.0188\; log\_\{10\}\{weight\; mathrm\{\; (g))\}\; imes\; height\; mbox\{\; (cm)\}^\{0.3\}$

and the National Cancer Institute formula Fact|date=February 2008:$\{BSA\}=(\{weight\; mbox\{\; (kg)^\{0.425\}\; imes\; \{height\; mbox\{\; (cm)^\{0.725\})\; /\; 139.315$

Normal values

"Normal" BSA is generally taken to be 1.7 m² for an adult.

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References

External links

* [http://www.bccancer.bc.ca/HPI/drugdatabase/appendices/appendix9.htm BC Cancer network] BSA calculation guidelines.
* [http://www.cato.eu/body-surface-area.html Online Body Surface Area Calculator (Dubois Formula)]
* [http://www.cato.eu/body-surface-area-children-1.html Online Body Surface Area Calculator (Mosteller Formula)]
* [http://www.webcooltools.com/Medicine/BSA.html Web CoolTool to Calculate BSA using any of the five formulae]