more about Standardization of Body Surface Area
As part of the review at the Cross Cancer Institute (CCI), three slide rules and one calculating device for calculation of body surface area, all of which are in current, clinical use on regular orders and in various trial protocols, were tested.
Although the original source for the estimation of surface area was given on only 2 of the 4 devices, all seemed to be based on the Du Bois formula, and predicted the same surface area over the wide range of combinations of height and weight tested.
Thirty-three orders containing the patient’s height, weight and BSA calculated by nursing were pulled over a nine day perion (from July 7-15, 1998), and nursing’s BSA results were compared to BSA results from the proposed equation (Table 2).
94% of the BSA calculated by nursing were similar to pharmacy’s calculations (0% to 4% difference). However, there was one BSA calculation that differed by 8% and another that differed by 14%. This would correspond to a 14% difference in the dose for this particular patient. Thus, 3% of the BSA calculations were observed to contain > 10% error.
A personal communication with Dr. B. Dana, the drug information Specialist at M.D. Anderson, confirms that, although there is no institutional standard, the center too uses the Mosteller Equation, however it does not use it for obese or underweight people. The British Columbia Cancer Agency now uses the Mosteller Equation for calculating BSA. Slide-rule type calculators whose results conform to this formula are also permitted, however all slide rules donated by pharmaceutical companies must come through pharmacy. A maximum of a 5% variance in dosage calculation is permitted at the BCCA.
According to Wang et al, the Mosteller Equation, ranks third for lowest RMSE9. The Mosteller Equation is a simple modification of the equation by Gehan and George which Wang et al ranked second for lowest RMSE. This formula is more convenient to apply in day-to-day clinical practice than a nomogram, provided a calculator with a square root function is available. Although a slight degree of accuracy has been lost by Mosteller in modifying the Gehan and George Equation, deviations from accepted values derived from other formulas are generally <2%4.
Lam and Leung calculated the BSA of 168 children between 1 month and 14 years of age using the equation proposed by Mosteller. The authors confirm that the Mosteller equation is equally applicable to children11. Carlo Quaia, an oncology pharmacist with the British Columbia Children’s Hospital, confirmed that the Mosteller equation is the standard formula used by BCCH for calculating BSA. Dr. B. Bell at the CCI agrees that using the Mosteller Equation in the pediatric population is acceptable.
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