What are the diagnostic criteria for failure to thrive (FTT)?

Diagnostic Criteria for Failure to Thrive (FTT)

Failure to thrive is defined as weight below the 10th percentile for age, weight that crosses two or more major percentile lines downward on standard growth charts, or weight-for-height below the 10th percentile. 1

Primary Diagnostic Criteria

• Weight-based criteria (any of the following):

  • Weight below the 10th percentile for age
  • Weight that crosses two or more major percentile lines downward
  • Weight-for-height/length below the 10th percentile

• Growth rate concerns:

  • Infants (0-6 months): weight gain less than 190 ± 152 g/month (~6.3 g/day)
  • Infants (6-12 months): weight gain less than 110 ± 111 g/month (~3.7 g/day)
  • Children (12-24 months): weight gain less than 71 ± 58 g/month (~2.4 g/day) 1

Assessment Parameters

• Essential measurements:

  • Accurate weight
  • Accurate length/height
  • Head circumference (particularly important in infants)
  • Weight-for-length ratio calculation
  • Rate of weight gain/loss over time 1

• Growth chart utilization:

  • Use World Health Organization (WHO) standards for children from birth to 2 years
  • Use Centers for Disease Control and Prevention (CDC) charts for children from age 2 years onward 2
  • For premature infants: use adjusted age and appropriate growth charts 1

Special Considerations

• Premature infants:

  • Expected to gain 17-20 g/kg/day (similar to the recommended target for children with FTT) 1
  • Extremely preterm infants (born before 28 weeks gestation) have different growth patterns and higher risk of FTT 1

• Normal growth pattern shifts:

  • Approximately 25% of normal infants will shift to a lower growth percentile in the first two years of life and then follow that percentile consistently; this should NOT be diagnosed as FTT 3

• Special populations:

  • Children with Down syndrome, intrauterine growth retardation, or prematurity follow different growth patterns than typical infants 3
  • Condition-specific growth charts should be used when available for conditions like skeletal dysplasia 4

Differential Diagnostic Considerations

FTT must be distinguished from short stature:

• FTT primarily affects weight, with height/length either unaffected or affected to a lesser degree
• Short stature primarily involves comparison of a child's height to reference groups or to their own height across time 2

Clinical Evaluation Components

• Detailed history:

  • Birth weight and gestational age
  • Feeding history (difficulties with nursing, formula preparation)
  • Family history of growth patterns
  • Medical conditions
  • Social/environmental factors 1, 2

• Physical examination:

  • Signs of malnutrition or underlying medical conditions
  • Developmental assessment
  • Dysmorphic features that might suggest genetic syndromes 1

• Laboratory testing:

  • Routine laboratory testing rarely identifies a cause and is not generally recommended unless specific clinical indicators are present 5

Etiological Categories

• Inadequate caloric intake:

  • Difficulties with nursing/feeding
  • Limited food availability
  • Incorrect formula preparation

• Inadequate caloric absorption:

  • Metabolic disorders
  • Gastrointestinal conditions

• Excessive caloric expenditure/ineffective utilization:

  • Hyperthyroidism
  • Diabetes
  • Pulmonary or cardiac conditions 2

The diagnostic approach to FTT should focus on accurate anthropometric measurements, careful plotting on appropriate growth charts, and thorough assessment of growth velocity, with special attention to the pattern of growth deceleration rather than just a single measurement point.