@who-growth/core

WHO Child Growth Standards calculator — z-scores, percentiles, and nutritional classification.

Zero dependencies. Works in Node.js, browsers, and edge runtimes.

Features

• 2 chart sets: WHO standard, Down syndrome (Zemel 2015)
• 6 growth indicators: weight-for-age, length/height-for-age, BMI-for-age, head circumference-for-age, weight-for-length, weight-for-height
• Full age range: 0–19 years (WHO), 0–18 years (Down syndrome)
• Prematurity correction: gestational age adjustment up to 2 years
• Nutritional classification: SISVAN/WHO cutpoints
• i18n: pt-BR, en, es
• LMS data: 26 official tables embedded, lazy-loaded

Chart Sets

| Chart Set | Status | Age Range | Indicators | |-----------|--------|-----------|------------| | WHO Standard | ✅ Complete | 0–19 years | All 6 | | Down Syndrome (Zemel 2015) | ✅ Complete | 0–20 years | WFA (0–18y), LFA (0–18y), BFA (0–18y), HCFA (0–20y) |

Install

npm install @who-growth/core

Usage

import { calculateZScore, calculateAll } from '@who-growth/core';

// Single indicator (WHO standard)
const result = await calculateZScore({
  indicator: 'weight-for-age',
  sex: 'male',
  ageInDays: 365,
  measurement: 9.5,
});
// → { indicator: 'weight-for-age', zScore: -0.11, percentile: 45.6 }

// Full assessment (WHO standard)
const assessment = await calculateAll({
  sex: 'female',
  dateOfBirth: new Date('2024-06-15'),
  dateOfMeasurement: new Date('2025-06-15'),
  weight: 9.2,
  lengthHeight: 74.5,
  headCircumference: 45,
  gestationalAgeWeeks: 34, // optional — triggers prematurity correction
});
// → { age, results, classifications }

// Down syndrome charts
const dsResult = await calculateAll({
  sex: 'male',
  dateOfBirth: new Date('2024-01-01'),
  dateOfMeasurement: new Date('2025-01-01'),
  weight: 8.5,
  lengthHeight: 70,
  chartSet: 'down-syndrome',
});

API

calculateZScore(input): Promise<ZScoreResult | null>

Calculate z-score and percentile for a single indicator.

Options:

• chartSet: 'who-standard' (default) | 'down-syndrome'

calculateAll(input): Promise<AssessmentResult>

Calculate all applicable indicators for a patient, including age calculation, prematurity correction, and nutritional classification.

computeZScore(measurement, lms): number

Low-level z-score calculation from measurement and LMS parameters. Implements the WHO standard formula with L=0 handling and |Z|>3 extrapolation.

classify(result, ageInDays): Classification

Classify a z-score result using SISVAN/WHO cutpoints.

ageInDays(dateOfBirth, dateOfMeasurement): number

Calculate age in days between two dates.

correctedAgeInDays(chronologicalDays, gestationalAgeWeeks?): number

Apply prematurity correction (up to 2 years of age).

Formulas

• Standard: Z = ((measurement/M)^L - 1) / (L × S)
• When L=0: Z = ln(measurement/M) / S
• |Z| > 3: WHO linear extrapolation method
• Percentile: Normal CDF (Abramowitz & Stegun approximation)

Data Sources

• WHO: WHO Anthro (0–5y) + WHO AnthroPlus (5–19y)
• Down Syndrome: Zemel BS, et al. Growth Charts for Children With Down Syndrome in the United States. Pediatrics. 2015;136(5):e1204-e1211.

License

MIT