BSA Estimation for a 10-Year-Old Girl Weighing 57.4 kg
For a 10-year-old girl weighing 57.4 kg, the estimated body surface area (BSA) is approximately 1.58 m² using the Mosteller formula, which is the most practical method when height is unavailable, though this represents a child with obesity requiring clinical evaluation.
Weight-Based BSA Calculation
- Using the Mosteller formula with an estimated height of 140 cm (50th percentile for age): BSA = √[(57.4 kg × 140 cm) / 3600] = 1.58 m² 1
- For children over 30 kg, weight-only estimation methods can be employed with acceptable accuracy, though precision decreases in obese children 2, 3
- The British National Formulary recommends BSA-based dosing for most pediatric medications, particularly chemotherapeutic agents 2, 3
Clinical Context and Obesity Assessment
- A weight of 57.4 kg at age 10 years places this child well above the 95th percentile, indicating obesity that requires immediate assessment for metabolic complications 4
- The expected weight for a 10-year-old girl at the 50th percentile is approximately 32 kg, making this child nearly 80% above expected weight for age 4
- This degree of obesity necessitates screening for cardiovascular risk factors, metabolic abnormalities, and endocrine disorders before proceeding with any BSA-dependent medication dosing 4
Important Dosing Caveats in Obesity
- Weight-only BSA estimation formulas have reduced precision in obese patients, with potential deviations up to 35% from measured values 2, 5
- The Mosteller formula underestimates BSA by approximately 4% overall, with lower precision (9.38%) in pediatric populations, particularly at extremes of body habitus 5
- For chemotherapeutic agents or drugs with narrow therapeutic indices, direct measurement of both height and weight is essential to minimize dosing errors 2, 5
Recommended Approach for Accurate BSA
- Obtain actual height measurement to calculate BSA using the Mosteller formula: BSA (m²) = √[(weight in kg × height in cm) / 3600] 1, 5
- If height measurement is impossible, use weight-based estimation with the understanding that accuracy is compromised in this obese patient 2, 3
- For high-risk medications, consider using alternative dosing parameters such as ideal body weight or adjusted body weight rather than actual BSA in significantly obese children 2
Growth Monitoring Requirements
- Plot BMI on CDC growth charts (used after 24 months of age) to visualize trajectory and confirm obesity classification 4
- Serial measurements every 2-4 months are recommended to track response to interventions and ensure appropriate growth velocity 4
- Assessment should include dietary patterns, physical activity levels, sleep habits, family history, and medication review as contributing factors 4