Pediatric Growth Assessment

Overview

Retrieve longitudinal height, weight, and head circumference Observations for a pediatric patient. Calculate age- and sex-specific percentiles and z-scores using WHO standards (0-2 years) and CDC growth charts (2-20 years). Assess growth velocity, BMI-for-age, and weight-for-length (under 2 years). Flag percentile crossing (shift of 2+ major percentile lines), failure to thrive criteria, obesity, and short stature triggers. Generate a structured growth assessment with referral recommendations when indicated.

FHIR Resources Used

Instructions

Step 1: Retrieve Patient Demographics

Tool: fhir_read
resourceType: "Patient"
id: "[patient-id]"

Extract birthDate (calculate exact age in years, months, days), gender (required for sex-specific charts). Confirm age is 0-20 years. If older than 20, this skill does not apply.

Step 2: Pull All Growth Observations

Tool: fhir_search
resourceType: "Observation"
queryParams: "patient=[patient-id]&code=29463-7,8302-2,9843-4,8287-5,39156-5&_sort=date&_count=200"

LOINC codes:

• 29463-7 = Body weight
• 8302-2 = Body height (standing)
• 8306-3 = Body height lying (recumbent length, used <2 years)
• 9843-4 = Head occipitofrontal circumference
• 8287-5 = Head circumference percentile
• 39156-5 = BMI

Also search for recumbent length separately if child is under 2:

Tool: fhir_search
resourceType: "Observation"
queryParams: "patient=[patient-id]&code=8306-3&_sort=date&_count=50"

For each Observation, extract:

• effectiveDateTime -- calculate age at measurement
• valueQuantity.value and valueQuantity.unit -- normalize to metric (kg, cm)
• Convert lbs to kg ( 0.453592), inches to cm ( 2.54) if needed

Step 3: Pull Growth-Related Conditions

Tool: fhir_search
resourceType: "Condition"
queryParams: "patient=[patient-id]&code=36857005,414916001,238131007,237837007,15628003&clinical-status=active"

SNOMED codes:

• 36857005 = Failure to thrive
• 414916001 = Obesity
• 238131007 = Overweight
• 237837007 = Short stature
• 15628003 = Growth hormone deficiency

Step 4: Select Appropriate Growth Chart

Based on age:

• Birth to 23 months: WHO growth standards
• Weight-for-age
• Length-for-age (recumbent)
• Weight-for-length
• Head circumference-for-age
• 2 to 20 years: CDC growth charts
• Weight-for-age
• Stature-for-age (standing height)
• BMI-for-age
• Preterm infants: Use corrected gestational age until 24 months for weight, 40 months for head circumference

See references/growth-chart-data.md for percentile lookup tables and z-score formulas.

Step 5: Calculate Percentiles and Z-Scores

For each measurement at each time point, calculate:

Z-score formula (LMS method):

• Z = ((X/M)^L - 1) / (L * S) when L != 0
• Z = ln(X/M) / S when L = 0

Where L, M, S are age- and sex-specific parameters from growth chart data tables.

Percentile from z-score: Use standard normal CDF approximation.

Classification by percentile:

• <1st percentile (z < -2.33): severely underweight/short
• 1st-3rd percentile (z -2.33 to -1.88): underweight/short -- monitor closely
• 3rd-5th percentile (z -1.88 to -1.65): low normal -- monitor
• 5th-85th percentile: normal range
• 85th-95th percentile (z 1.04 to 1.65): overweight (BMI-for-age)
• >=95th percentile (z >= 1.65): obese (BMI-for-age)
• >=99th percentile (z >= 2.33): severe obesity

Step 6: Assess Growth Velocity

Calculate growth velocity between consecutive measurements:

Height velocity (cm/year):

• (height2 - height1) / (age2 - age1 in years)

Compare to age-specific norms (see references/growth-abnormalities.md):

• Infancy (0-1 year): 23-27 cm/year
• Toddler (1-2 years): 10-14 cm/year
• Childhood (2-puberty): 5-7 cm/year
• Pubertal growth spurt: 8-14 cm/year (girls peak ~12y, boys peak ~14y)

Weight velocity (grams/day for infants, kg/year for children):

• Newborn: 20-30 g/day (first 3 months)
• Infant 3-6 months: 15-20 g/day
• Infant 6-12 months: 10-15 g/day

Flag growth velocity below 25th percentile for age.

Step 7: Detect Percentile Crossing

Compare percentiles across time points. Flag if:

• Weight-for-age crosses downward through 2 or more major percentile lines (5th, 10th, 25th, 50th, 75th, 90th, 95th)
• Height-for-age crosses downward through 2 or more major percentile lines
• Weight-for-age drops below 5th percentile
• Head circumference crosses 2+ percentile lines in either direction (macrocephaly or microcephaly)
• BMI-for-age crosses upward through 85th or 95th percentile

Step 8: Evaluate Failure to Thrive Criteria

FTT is flagged if any of:

• Weight < 5th percentile for age on more than one occasion
• Weight deceleration crossing 2+ major percentile lines
• Weight-for-length < 5th percentile (under 2 years)
• BMI-for-age < 5th percentile (2-20 years)
• Weight velocity < 50% of expected for age

If FTT criteria met, check for:

Tool: fhir_search
resourceType: "Condition"
queryParams: "patient=[patient-id]&clinical-status=active"

Look for organic causes: GERD, celiac disease, cystic fibrosis, congenital heart disease, metabolic disorders.

Step 9: Calculate BMI-for-Age (Children >= 2 Years)

BMI = weight (kg) / height (m)^2

Classify using CDC BMI-for-age percentiles:

• <5th percentile: underweight
• 5th to <85th: healthy weight
• 85th to <95th: overweight
• >=95th: obese
• >=120% of 95th percentile: severe obesity

Step 10: Format Output

PEDIATRIC GROWTH ASSESSMENT -- [Patient Name]
DOB: [date] | Age: [Y]y [M]m | Sex: [M/F]
Growth Chart: [WHO 0-2 / CDC 2-20]
=============================================

CURRENT MEASUREMENTS ([date])
  Weight: [value] kg ([percentile]th %ile, z=[z-score])
  Height: [value] cm ([percentile]th %ile, z=[z-score])
  Head circ: [value] cm ([percentile]th %ile, z=[z-score])  [if <3 years]
  BMI: [value] kg/m2 ([percentile]th %ile, z=[z-score])     [if >=2 years]

GROWTH TRAJECTORY
  [Date1]: Wt [val] ([%ile]), Ht [val] ([%ile]), HC [val] ([%ile])
  [Date2]: Wt [val] ([%ile]), Ht [val] ([%ile]), HC [val] ([%ile])
  ...
  Trend: [stable / upward crossing / downward crossing / decelerating]

GROWTH VELOCITY
  Height velocity: [value] cm/year [normal / below expected]
  Weight velocity: [value] g/day or kg/year [normal / below expected]

FLAGS
  [!] [Description of any concerning finding]
  ...

ASSESSMENT
  [Overall growth status: normal / FTT / overweight / obese / short stature]

RECOMMENDATIONS
  [Specific actions: monitor, dietary evaluation, labs, referral]

Examples

Example 1: Normal Well-Child Growth Check

User says: "Check growth for patient PED-2201, 15-month well child visit"

Actions:

1. fhir_read Patient/PED-2201 -- 15-month-old male
2. fhir_search Observation?patient=PED-2201&code=29463-7,8302-2,8306-3,9843-4&_sort=date&_count=200 -- returns measurements from birth, 2mo, 4mo, 6mo, 9mo, 12mo, 15mo visits
3. fhir_search Condition?patient=PED-2201&clinical-status=active -- no growth-related conditions

Result:

PEDIATRIC GROWTH ASSESSMENT -- Liam Chen
DOB: 2024-11-07 | Age: 1y 3m | Sex: Male
Growth Chart: WHO 0-2
=============================================

CURRENT MEASUREMENTS (2026-02-07)
  Weight: 10.8 kg (55th %ile, z=0.13)
  Length: 79.5 cm (60th %ile, z=0.25)
  Head circ: 47.2 cm (50th %ile, z=0.00)

GROWTH TRAJECTORY
  Birth:  3.4 kg (45th), 50 cm (42nd), HC 34.5 cm (48th)
  6mo:    7.8 kg (50th), 67 cm (48th), HC 43.5 cm (50th)
  12mo:   9.9 kg (50th), 76 cm (55th), HC 46.2 cm (48th)
  15mo:  10.8 kg (55th), 79.5 cm (60th), HC 47.2 cm (50th)
  Trend: STABLE -- tracking along 50th-60th percentile corridor

GROWTH VELOCITY
  Height: 26 cm/year (first year), 14 cm/year (12-15mo) [NORMAL]
  Weight: 24 g/day (first 3mo) [NORMAL]

ASSESSMENT: Normal growth pattern. All parameters tracking appropriately.

Example 2: Failure to Thrive Evaluation

User says: "Growth assessment for patient PED-5590, parents concerned about weight gain"

Actions:

1. fhir_read Patient/PED-5590 -- 10-month-old female
2. fhir_search Observation?patient=PED-5590&code=29463-7,8302-2,8306-3,9843-4&_sort=date&_count=200 -- shows weight percentile dropping: birth 50th, 4mo 35th, 6mo 15th, 9mo 5th, 10mo 3rd
3. fhir_search Condition?patient=PED-5590&clinical-status=active -- GERD documented

Result:

PEDIATRIC GROWTH ASSESSMENT -- Sophia Martinez
DOB: 2025-04-07 | Age: 0y 10m | Sex: Female
Growth Chart: WHO 0-2
=============================================

CURRENT MEASUREMENTS (2026-02-07)
  Weight: 7.1 kg (3rd %ile, z=-1.88)
  Length: 70.5 cm (25th %ile, z=-0.67)
  Head circ: 44.8 cm (45th %ile, z=-0.13)
  Weight-for-length: 3rd %ile (z=-1.88)

GROWTH TRAJECTORY
  Birth:  3.3 kg (50th), 49 cm (45th), HC 34 cm (50th)
  4mo:    5.8 kg (35th), 62 cm (35th), HC 40 cm (42nd)
  6mo:    6.4 kg (15th), 65 cm (28th), HC 42 cm (45th)
  9mo:    6.8 kg (5th),  68 cm (22nd), HC 44 cm (44th)
  10mo:   7.1 kg (3rd),  70.5 cm (25th), HC 44.8 cm (45th)
  Trend: DOWNWARD CROSSING -- weight crossed from 50th to 3rd percentile

FLAGS
  [!] FAILURE TO THRIVE CRITERIA MET
      - Weight crossed downward through 3 major percentile lines (50th->35th->15th->3rd)
      - Weight-for-length at 3rd percentile
      - Weight velocity: 8 g/day (months 6-10) -- below expected 10-15 g/day
  [!] Known GERD -- potential organic contributor to poor weight gain
  [!] Length sparing: height at 25th percentile while weight at 3rd -- suggests nutritional FTT

RECOMMENDATIONS
  - Dietary assessment: caloric intake evaluation, feeding observation
  - Laboratory workup: CBC, CMP, celiac panel (tTG-IgA), thyroid, urinalysis
  - Consider increasing caloric density of feeds
  - GERD management optimization -- assess current treatment adequacy
  - Follow-up weight check in 2 weeks
  - Refer to pediatric GI if no improvement in 4 weeks

Troubleshooting

Growth Observations Use Non-Standard LOINC Codes

• Some EHR systems use LOINC 3141-9 (body weight measured) instead of 29463-7. Try both.
• Recumbent length may be coded as LOINC 8306-3 or 89269-5. Search without code filter and inspect available Observation codes.
• Head circumference may use LOINC 8287-5 (percentile) instead of 9843-4 (actual measurement).

Measurements in Non-Metric Units

• Convert on the fly: lbs to kg ( 0.453592), inches to cm ( 2.54), oz to g (* 28.3495).
• Check valueQuantity.unit for [lb_av], [in_i], lb, in, oz.
• WHO/CDC chart data uses metric. All calculations must be in kg and cm.

Insufficient Data Points for Velocity Calculation

• Need at least 2 measurements separated by >=1 month for meaningful velocity.
• If only one measurement exists, calculate percentile and z-score but note velocity cannot be assessed.
• Recommend establishing baseline with follow-up measurement.

Related Skills

• lab-result-interpreter -- for FTT laboratory workup interpretation
• immunization-status-checker -- often combined with well-child growth checks
• clinical-summary-generator -- for comprehensive pediatric summary
• preventive-care-compliance-report -- for well-child visit schedule adherence