BSA body surface area in Clinical Trials

Unlike the prevalent known normal range(18–25) for BMI (body mass index) score. The BSA(body surface index)’s normal range is less known. Although BSA is also important in Clinical Trials and many medical measurements, including the calculation of drug dosages and the amount of fluids to be administered IV, especially in Dermatology.

One day, when I reviewed the BSA block in a demographic table, the number matched, but it didn't make sense. Because it is extremely large (over 30) compared to the normal range (around 1–2). My colleague and I looked into the data, and we found out the unit for BSA caused the large result.

There are three types of BSA units.

1. BSA /m²
   bsa = 0.007184 * (weight kg ^0.425) * (height cm ^0.725)
   The most commonly used formula now is that of Mosteller, published in 1987 in The New England Journal of Medicine. According to Mosteller’s “simplified calculation of body-surface area In metric terms,” the body surface area = the square root of the product of the weight in kg times the height in cm divided by 3600.
   bsa=sqrt(weight kg* height cm)/ 3600
2. BSA/ ft²
3. BSA %

• Average body surface area for adult men: 1.9 m2
• Average body surface area for adult women: 1.6 m2
• Average body surface area for children (9 years): 1.07 m2
• Average body surface area for children (10 years): 1.14 m2
• Average body surface area for children (12–13 years): 1.33 m2

We are used to the BSA unit being m² and forgot the other possibilities. Sometimes, the meaning behind the number is more important than the number itself!

Thanks Mike.S for investigating the BSA unit with me !

Happy Coding!

Ref https://www.rxlist.com/body_surface_area/definition.htm