Body surface area

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Short description: Drug Calculating formula

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, such as chemotherapy.

Typically there is a 4–10 fold variation in drug clearance between individuals due to differing the activity of drug 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 in Phase I and II trials that may result in potentially helpful medications being prematurely rejected.[1][2] The trend to personalized medicine is one approach to counter this weakness.

Uses

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]

Calculation

Various calculations have been published to arrive at the BSA without direct measurement. In the following formulae, BSA is expressed in m2, weight (or, more properly, mass) W in kg, and height H in cm.

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]

[math]\displaystyle{ {BSA}=0.007184 \times W^{0.425} \times H^{0.725} }[/math]

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

[math]\displaystyle{ {BSA }= \frac{\sqrt{W \times H}}{60} = 0.016667 \times W^{0.5} \times H^{0.5} }[/math]

Other formulas for BSA in m2 include:

Haycock[8] [math]\displaystyle{ 0.024265 \times W^{0.5378} \times H^{0.3964} }[/math]
Gehan and George[9]     [math]\displaystyle{ 0.0235 \times W^{0.51456} \times H^{0.42246} }[/math]
Boyd [10] [math]\displaystyle{ 0.03330 \times W^{(0.6157 - 0.0188 \log_{10} {W})} \times H^{0.3} }[/math]
    or alternatively     [math]\displaystyle{ 0.0003207 \times \mathrm{weight} \mathrm{(g)}^{(0.7285 - 0.0188 \log_{10}{\mathrm{weight} \mathrm{ (g)}})} \times H^{0.3} }[/math]
Fujimoto[11] [math]\displaystyle{ 0.008883 \times W^{0.444} \times H^{0.663} }[/math]
Takahira[11] [math]\displaystyle{ 0.007241 \times W^{0.425} \times H^{0.725} }[/math]
Shuter and Aslani[12] [math]\displaystyle{ 0.00949 \times W^{0.441} \times H^{0.655} }[/math]
Lipscombe [13]     [math]\displaystyle{ 0.00878108 \times W^{0.434972} \times H^{0.67844} }[/math]
Schlich[14] [math]\displaystyle{ 0.000975482 \times W^{0.46} \times H^{1.08} }[/math]       (women)
[math]\displaystyle{ 0.000579479 \times W^{0.38} \times H^{1.24} }[/math]       (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 [math]\displaystyle{ {8/900} \times W^{4/9} \times H^{2/3} }[/math], which is dimensionally correct for the case of constant density. It equals [math]\displaystyle{ (2^3/3^2) \times (W^{2/3} H) ^ {2/3} /100 }[/math].

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 [4W (kg) + 7]/[90 + W (kg)].[15][16]

Average values

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

Mean male BSA by age
Age or age group metric imperial
Neonate (newborn) 0.243 m2 2.612 ft2
2 years 0.563 m2 6.060 ft2
5 years 0.787 m2 8.471 ft2
10 years 1.236 m2 13.304 ft2
13 years 1.603 m2 17.255 ft2
18 years 1.980 m2 21.313 ft2
20–79 years 2.060 m2 22.173 ft2
80+ years 1.920 m2 20.667 ft2
Mean female BSA by age
Age or age group metric imperial
Neonate (newborn) 0.234 m2 2.519 ft2
2 years 0.540 m2 5.813 ft2
5 years 0.771 m2 8.299 ft2
10 years 1.245 m2 13.401 ft2
13 years 1.550 m2 16.684 ft2
18 years 1.726 m2 18.579 ft2
20–79 years 1.830 m2 19.697 ft2
80+ years 1.638 m2 17.631 ft2

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]

References

  1. ↑ Gurney H (April 2002). "How to calculate the dose of chemotherapy". Br. J. Cancer 86 (8): 1297–302. doi:10.1038/sj.bjc.6600139. PMID 11953888. 
  2. ↑ "Dose calculation of anticancer drugs". Expert Opin Drug Metab Toxicol 4 (10): 1307–19. October 2008. doi:10.1517/17425255.4.10.1307. PMID 18798700. 
  3. ↑ Adler, AC; Nathanson, BH; Raguhunathan, K; McGee, WT (2012). "Misleading indexed hemodynamic parameters: the clinical importance of discordant BMI and BSA at extremes of weight". Critical Care 16 (6): 471. doi:10.1186/cc11876. PMID 23273020. 
  4. ↑ "A formula to estimate the approximate surface area if height and weight be known". Archives of Internal Medicine 17 (6): 863–71. Jun 1916. doi:10.1001/archinte.1916.00080130010002. https://zenodo.org/record/1423319.  Reprinted in PMID 2520314
  5. ↑ Verbraecken, J; Van de Heyning P; De Backer W; Van Gaal L (Apr 2006). "Body surface area in normal-weight, overweight, and obese adults. A comparison study". Metabolism: Clinical and Experimental 55 (4): 515–24. doi:10.1016/j.metabol.2005.11.004. PMID 16546483. http://www.metabolismjournal.com/article/S0026-0495(05)00437-3/abstract. Retrieved 2012-09-07. 
  6. ↑ Sardinha, LB; Silva, AM; Minderico, CS; Teixeira, PJ (2006). "Effect of body surface area calculations on body fat estimates in non-obese and obese subjects.". Physiological Measurement 27 (11): 1197–209. doi:10.1088/0967-3334/27/11/012. PMID 17028412. Bibcode: 2006PhyM...27.1197S. 
  7. ↑ Mosteller, RD (1987). "Simplified calculation of body-surface area". N Engl J Med 317 (17): 1098. doi:10.1056/NEJM198710223171717. PMID 3657876. 
  8. ↑ Haycock, GB; Schwartz, GJ; Wisotsky, DH (1978). "Geometric method for measuring body surface area: A height-weight formula validated in infants, children and adults". J Pediatr 93 (1): 62–66. doi:10.1016/s0022-3476(78)80601-5. PMID 650346. 
  9. ↑ Gehan EA, George SL, Cancer Chemother Rep 1970, 54:225-235
  10. ↑ 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.
  11. ↑ 11.0 11.1 Fujimoto, S; Watanabe, T; Sakamoto, A; Yukawa, K; Morimoto, K (1968). "Studies on the physical surface area of Japanese. 18. Calculation formulae in three stages over all ages". Nippon Eiseigaku Zasshi 23 (5): 443–50. doi:10.1265/jjh.23.443. PMID 5752712. 
  12. ↑ Shuter, B; Aslani, A (2000). "Body surface area: Du bois and Du bois revisited". European Journal of Applied Physiology 82 (3): 250–254. doi:10.1007/s004210050679. PMID 10929220. 
  13. ↑ Lipscombe, Trevor, Body Surface Area Formula by Use of Geometric Means Medicina Internacia Revuo 2020, 29 (114):11-18
  14. ↑ Schlich, E; Schumm, M; Schlich, M (2010). "3-D-Body-Scan als anthropometrisches Verfahren zur Bestimmung der spezifischen Körperoberfläche". Ernährungs Umschau 57 (4): 178–183. https://www.ernaehrungs-umschau.de/print-artikel/12-04-2010-the-3d-body-scan-as-an-anthropometric-analysis-to-measure-the-specific-body-surface/. 
  15. ↑ 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.
  16. ↑ Furqan, M; Haque, A (December 2009). "Surface area in children: a simple formula.". Indian Pediatrics 46 (12): 1085–7. PMID 19430073. 
  17. ↑ Georgiev, Georgi. "Body Surface Area Calculator". https://www.gigacalculator.com/calculators/bsa-calculator.php. 
  18. ↑ "National Health and Nutrition Examination Survey". https://www.cdc.gov/nchs/nhanes/index.htm. 
  19. ↑ "Paclitaxel Pharmacokinetics, Threshold Models, and Dosing Strategies". Journal of Clinical Oncology 21 (14): 2803–4. 15 Jul 2003. doi:10.1200/JCO.2003.99.038. PMID 12860961. 
  20. ↑ "The Average Body Surface Area of Adult Cancer Patients in the UK: A Multicentre Retrospective Study". PLoS One 5 (1): e8933. 28 Jan 2010. doi:10.1371/journal.pone.0008933. PMID 20126669. PMC 2812484. Bibcode: 2010PLoSO...5.8933S. http://ukpmc.ac.uk/articles/PMC2812484/reload=0;jsessionid=VMxGfFGKF2er3zi0XF6N.4. Retrieved 2012-09-09. 



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