BMI & BSA Calculator

Overview

Clinical calculator for anthropometric measurements used in health assessment, obesity screening, and chemotherapy dosing calculations.

Key Capabilities:

- BMI Calculation: Standard and adjusted BMI formulas
BSA Estimation: Multiple validated formulas (DuBois, Mosteller, Haycock)
Weight Classification: WHO and CDC category assignment
Dosing Support: Chemotherapy and medication dose calculations
Pediatric Support: Age-appropriate norms and calculations
Unit Flexibility: Metric and imperial input support

When to Use

✅ Use this skill when:

- Calculating chemotherapy doses requiring BSA (mg/m²)
Screening for obesity or underweight in clinical practice
Adjusting drug doses based on body composition
Documenting baseline anthropometrics in patient charts
Teaching medical students clinical calculations
Quick assessment in resource-limited settings

❌ Do NOT use when:

- BMI alone for clinical diagnosis → Use comprehensive metabolic assessment
Pregnancy weight assessment → Use gestational weight gain charts
Pediatric growth evaluation → Use WHO/CDC growth charts with percentiles
Body composition analysis → Use DEXA or bioimpedance
Athletic/muscular patients → Consider body fat % instead of BMI

Integration:

- Upstream: ehr-semantic-compressor (patient data extraction), automated-soap-note-generator (vital signs)
Downstream: drug-interaction-checker (dose calculation), medication-reconciliation (dosing verification)

Core Capabilities

1. BMI Calculation

Calculate Body Mass Index with classification:

CODEBLOCK0

BMI Categories (WHO):

Category	BMI Range	Clinical Significance
Underweight	< 18.5	Malnutrition risk
Normal

Adjusted BMI:

- BMI Prime: BMI / 25 (obesity severity index)
Ponderal Index: BMI for tall/short individuals
Age-adjusted: For elderly patients (>65)

2. BSA Calculation

Multiple formulas for different clinical scenarios:

CODEBLOCK1

BSA Formulas:

Formula	Equation	Best For
DuBois	0.007184 × W^0.425 × H^0.725	Adults (most common)
Mosteller

√(W × H / 3600) | Adults (simplified) |
| Haycock | 0.024265 × W^0.5378 × H^0.3964 | Pediatrics |
| Gehan-George | 0.0235 × W^0.51456 × H^0.42246 | Oncology |
| Yu | 0.015925 × W^0.5 × H^0.5 | Asian populations |

3. Drug Dosing Calculations

Apply BSA to medication dosing:

CODEBLOCK2

Common BSA-Based Doses:

- Carboplatin: AUC-based (Calvert formula)
5-FU: 400-600 mg/m²
Doxorubicin: 60-75 mg/m² (lifetime max 450-550 mg/m²)
Paclitaxel: 135-175 mg/m²

4. Pediatric Calculations

Age-appropriate calculations for children:

CODEBLOCK3

Pediatric Considerations:

- BMI percentiles (not absolute values)
Growth chart integration
Age-specific BSA formulas
Body composition changes with development

Common Patterns

Pattern 1: Chemotherapy Dosing

Scenario: Calculate carboplatin dose for cancer patient.

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Output:
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Pattern 2: Obesity Screening

Scenario: BMI assessment for weight management clinic.

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Pattern 3: Pediatric Growth Assessment

Scenario: Calculate child's BSA for medication dosing.

CODEBLOCK7

Pattern 4: Rapid Clinical Assessment

Scenario: Quick BMI/BSA for admission vital signs.

CODEBLOCK8

Complete Workflow Example

Comprehensive patient assessment:

CODEBLOCK9

Quality Checklist

Input Validation:

- [ ] Weight realistic (2-300 kg range)
[ ] Height realistic (50-250 cm range)
[ ] Units clearly specified (kg/lbs, cm/in)
[ ] Age appropriate for formulas used

Calculation Accuracy:

- [ ] Formula selection appropriate for patient
[ ] BSA formula matches clinical context
[ ] Pediatric vs. adult norms correctly applied
[ ] Rounding appropriate (1-2 decimal places)

Clinical Interpretation:

- [ ] CRITICAL: BMI is screening tool, not diagnostic
[ ] Ethnicity-specific cutoffs considered
[ ] Muscle mass considered (athletes)
[ ] Age adjustments applied (elderly/children)

Documentation:

- [ ] Formula used documented (DuBois vs. Mosteller)
[ ] Units clearly stated
[ ] Date of calculation recorded
[ ] Dose limits verified for chemotherapy

Common Pitfalls

Calculation Errors:

- ❌ Unit confusion → Pounds vs. kg, inches vs. cm

- ✅ Always verify units; convert if necessary

- ❌ Wrong formula → Using adult BSA for infants

- ✅ Use Haycock for children < 12 years

- ❌ BMI over-interpretation → Diagnosing based on BMI alone

- ✅ BMI is screening tool; clinical correlation required

Clinical Misuse:

- ❌ Athletes misclassified → Muscular patients marked obese

- ✅ Consider waist circumference or body fat %

- ❌ Elderly inappropriate norms → Same cutoffs for all ages

- ✅ Use age-adjusted BMI for >65 years

- ❌ Ignoring ethnicity → Universal cutoffs applied

- ✅ Asian populations: lower obesity thresholds

Dosing Errors:

- ❌ BSA rounding → 1.79 m² rounded to 1.8 m²

- ✅ Use precise values for chemotherapy

- ❌ Max dose ignored → Exceeding lifetime limits

- ✅ Always check cumulative doses (doxorubicin)

References

Available in references/ directory:

- bsa_formulas_comparison.md - Formula accuracy by population
INLINECODE6 - Growth charts and percentiles
INLINECODE7 - BSA-based drug calculations
INLINECODE8 - Population-specific cutoffs
INLINECODE9 - Comparison with reference standards

Scripts

Located in scripts/ directory:

- main.py - CLI calculator interface
INLINECODE12 - Core BMI/BSA calculations
INLINECODE13 - Multiple BSA formula implementations
INLINECODE14 - Child-specific calculations
INLINECODE15 - Medication dose calculations
INLINECODE16 - Clinical report generation

Limitations

- BMI Limitations: Doesn't distinguish fat from muscle; varies by ethnicity
BSA Estimation: All formulas are approximations; 10-15% variation normal
Extreme Values: Very short/tall patients may have inaccurate estimates
Not for Diagnosis: BMI/BSA are tools, not clinical diagnoses
Amputees: Standard formulas inaccurate; adjustment needed
Pregnancy: Special considerations not included

Parameters

Parameter	Type	Default	Required	Description
INLINECODE17, INLINECODE18	float	-	Yes	Weight in kilograms
INLINECODE19, INLINECODE20

Usage

Basic Usage

CODEBLOCK10

Risk Assessment

Risk Indicator	Assessment	Level
Code Execution	Python script executed locally	Low
Network Access

Security Checklist

- [x] No hardcoded credentials or API keys
[x] No unauthorized file system access
[x] Input validation for weight/height
[x] Output does not expose sensitive information
[x] Error messages sanitized
[x] Script execution in sandboxed environment

Prerequisites

CODEBLOCK11

Evaluation Criteria

Success Metrics

- [x] Successfully calculates BMI using standard formula
[x] Successfully calculates BSA using DuBois formula
[x] Correctly categorizes BMI (Underweight, Normal, Overweight, Obese)
[x] Calculates drug doses based on BSA when provided

Test Cases

1. Normal Adult: 70kg, 175cm → BMI 22.9 (Normal), BSA ~1.85 m²
Drug Dosing: 70kg, 175cm, 100mg/m² → Dose 185mg
JSON Output: Valid JSON with all fields

Lifecycle Status

- Current Stage: Draft
Next Review Date: 2026-03-06
Known Issues: None
Planned Improvements:

- Add additional BSA formulas (Haycock, Mosteller) - Add pediatric BMI percentiles - Add unit conversion (lbs, ft/in)

⚕️ Clinical Note: BMI and BSA are screening and calculation tools, not substitutes for clinical judgment. Always correlate with physical examination, patient history, and other assessments. Double-check all chemotherapy calculations independently.

BMI & BSA 计算器

概述

用于健康评估、肥胖筛查和化疗剂量计算的人体测量临床计算器。

关键功能：

- BMI 计算：标准及调整后的 BMI 公式
BSA 估算：多种经过验证的公式（DuBois、Mosteller、Haycock）
体重分类：WHO 和 CDC 类别分配
剂量支持：化疗和药物剂量计算
儿科支持：适龄标准和计算
单位灵活性：支持公制和英制输入

使用时机

✅ 使用此技能的场景：

- 计算需要 BSA 的化疗剂量（mg/m²）
临床实践中筛查肥胖或体重不足
根据身体成分调整药物剂量
在患者病历中记录基线人体测量数据
教授医学生临床计算方法
资源有限环境下的快速评估

❌ 不应使用的场景：

- 仅凭 BMI 进行临床诊断 → 应使用综合代谢评估
孕期体重评估 → 应使用妊娠期体重增长图表
儿科生长发育评估 → 应使用包含百分位的 WHO/CDC 生长曲线
身体成分分析 → 应使用 DEXA 或生物电阻抗
运动员/肌肉发达患者 → 应考虑体脂百分比而非 BMI

集成：

- 上游：ehr-semantic-compressor（患者数据提取）、automated-soap-note-generator（生命体征）
下游：drug-interaction-checker（剂量计算）、medication-reconciliation（剂量验证）

核心功能

1. BMI 计算

计算身体质量指数并进行分类：

python
from scripts.calculator import BMIBSACalculator

calc = BMIBSACalculator()

计算 BMI

result = calc.calculate_bmi( weight_kg=70, height_cm=175, age=45, sex=male )

print(fBMI: {result.bmi:.1f} kg/m²)
print(f类别: {result.category}) # 正常体重
print(f理想体重范围: {result.idealweightrange})

BMI 分类（WHO）：

类别	BMI 范围	临床意义
体重不足	< 18.5	营养不良风险
正常

18.5 - 24.9 | 健康范围 |
| 超重 | 25.0 - 29.9 | 风险增加 |
| 肥胖 I 级 | 30.0 - 34.9 | 高风险 |
| 肥胖 II 级 | 35.0 - 39.9 | 非常高风险 |
| 肥胖 III 级 | ≥ 40.0 | 极高风险 |

调整后的 BMI：

- BMI Prime：BMI / 25（肥胖严重程度指数）
Ponderal 指数：适用于高/矮个体的 BMI
年龄调整：适用于老年患者（>65岁）

2. BSA 计算

适用于不同临床场景的多种公式：

python

使用不同公式计算 BSA

bsaresults = calc.calculatebsa(
weight_kg=70,
height_cm=175,
formulas=[dubois, mosteller, haycock, gehan_george]
)

for formula, bsa in bsa_results.items():
print(f{formula}: {bsa:.2f} m²)

BSA 公式：

公式	方程式	最佳适用
DuBois	0.007184 × W^0.425 × H^0.725	成人（最常用）
Mosteller

√(W × H / 3600) | 成人（简化版） |
| Haycock | 0.024265 × W^0.5378 × H^0.3964 | 儿科 |
| Gehan-George | 0.0235 × W^0.51456 × H^0.42246 | 肿瘤学 |
| Yu | 0.015925 × W^0.5 × H^0.5 | 亚洲人群 |

3. 药物剂量计算

将 BSA 应用于药物剂量计算：

python

计算化疗剂量

dose = calc.calculate_dose(
bsa=bsa_results[dubois],
drug=carboplatin,
doseperm2=400, # mg/m²
max_dose=800 # mg 上限
)

print(f计算剂量: {dose:.0f} mg)
print(f使用的 BSA: {bsa_results[dubois]:.2f} m²)

常见基于 BSA 的剂量：

- 卡铂：基于 AUC（Calvert 公式）
5-氟尿嘧啶：400-600 mg/m²
阿霉素：60-75 mg/m²（终身最大剂量 450-550 mg/m²）
紫杉醇：135-175 mg/m²

4. 儿科计算

适用于儿童的年龄相关计算：

python
pediatric = calc.pediatric_mode(
weight_kg=25,
height_cm=120,
age_years=8,
sex=female
)

print(f年龄别 BMI 百分位: {pediatric.bmi_percentile}%)
print(f体重状况: {pediatric.weight_status})
print(fBSA（Haycock）: {pediatric.bsa:.2f} m²)

儿科注意事项：

- BMI 百分位（非绝对值）
生长曲线集成
特定年龄的 BSA 公式
随发育变化的身体成分

常见模式

模式 1：化疗剂量计算

场景：计算癌症患者的卡铂剂量。

bash

计算 BSA 和剂量

python scripts/main.py \
--weight 70 \
--height 175 \
--drug carboplatin \
--target-auc 5 \
--creatinine-clearance 80 \
--output dose_calculation.txt

输出：

BSA（DuBois）: 1.79 m²
Calvert 公式: 剂量 = 目标 AUC × (GFR + 25)
= 5 × (80 + 25)
= 525 mg
最大剂量检查: 525 mg ≤ 800 mg ✓
推荐剂量: 525 mg

模式 2：肥胖筛查

场景：体重管理门诊的 BMI 评估。

python

全面评估 BMI

assessment = calc.assess_bmi(
weight_kg=95,
height_cm=165,
age=52,
sex=female,
waist_cm=98
)

print(fBMI: {assessment.bmi:.1f}（肥胖 II 级）)
print(f腰围身高比: {assessment.whtr:.2f}（高风险）)
print(f合并症风险: {assessment.health_risk})
print(f建议: {assessment.recommendations})

模式 3：儿科生长发育评估

场景：计算儿童的 BSA 用于药物剂量。

python

儿科剂量

child = calc.pediatric_assessment(
weight_kg=20,
height_cm=110,
age_years=6,
sex=male
)

print(fBSA: {child.bsa:.2f} m²（Haycock 公式）)
print(fBMI 百分位: {child.bmi_percentile}th)
print(f阿霉素剂量: {child.bsa * 60:.0f} mg)

模式 4：快速临床评估

场景：入院生命体征的快速 BMI/BSA 计算。

bash

快速计算

python scripts/main.py --weight 80 --height 180 --quick

输出：

BMI: 24.7 kg/m²（正常）

BSA: 2.00 m²（DuBois）

理想体重: 65-80 kg

完整工作流程示例

全面患者评估：

python
from scripts.calculator import BMIBSACalculator
from scripts.reports import ClinicalReport

初始化

calc = BMIBSACalculator() report = ClinicalReport()

患者数据

patient = { weight_kg: 75, height_cm: 170, age: 55, sex: female, waist_cm: 88 }

计算所有指标

bmi = calc.calculate_bmi(patient) bsa = calc.calculate_bsa(patient, formula=dubois) assessment = calc.comprehensive_assessment(patient)

生成报告

report_data = { bmi: bmi, bsa

bmi-bsa-calculatorBMI与体表面积计算