What initial laboratory tests are recommended for a child with growth failure?

Initial Laboratory Tests for a Child with Growth Failure

The recommended initial laboratory tests for a child with growth failure include complete blood count, comprehensive metabolic panel, thyroid function tests (TSH and free T4), inflammatory markers, celiac disease screening, and chromosomal microarray testing.

Understanding Growth Failure

Growth failure in children is a significant indicator of underlying health issues that requires thorough evaluation. It can result from various causes including nutritional deficiencies, endocrine disorders, chronic diseases, and genetic conditions.

Initial Laboratory Evaluation

First-line Laboratory Tests

• Complete blood count (CBC) to assess for anemia, infection, or malignancy 1
• Comprehensive metabolic panel including:
  • Electrolytes to evaluate metabolic status 1
  • Liver function tests to screen for liver disease 1
  • Kidney function tests to assess for chronic kidney disease 1
  • Serum albumin to evaluate nutritional status 1
• Thyroid function tests (TSH and free T4) to screen for hypothyroidism 1
• Inflammatory markers (ESR, CRP) to assess for chronic inflammation 2
• Celiac disease screening with tissue transglutaminase antibodies 1
• Chromosomal microarray as first-tier genetic testing 1

Additional Testing Based on Clinical Presentation

• Bone age assessment via wrist radiography to evaluate skeletal maturation 1
• Growth hormone stimulation testing if growth hormone deficiency is suspected 1, 3
• Insulin-like growth factor 1 (IGF-1) levels to assess growth hormone axis 1
• Vitamin D, calcium, phosphorus, and PTH levels if metabolic bone disease is suspected 1
• Fragile X testing, particularly in males with developmental delays 1
• Karyotype if specific chromosomal disorders are suspected 1

Special Considerations for Specific Conditions

Chronic Kidney Disease

• Additional testing should include:
  • Serum bicarbonate to assess for metabolic acidosis 1
  • 25-hydroxyvitamin D3 levels (target >30 ng/ml) 1
  • Parathyroid hormone (PTH) levels 1

Suspected Genetic Syndromes

• Microarray testing is recommended as the first-line chromosome study for children with growth failure and dysmorphic features 1
• Consider exome sequencing if initial genetic testing is negative but genetic etiology is still suspected 1

Endocrine Disorders

• For suspected thyroid disorders, measure TSH and free T4 1
• For suspected growth hormone deficiency, measure IGF-1 levels and consider growth hormone stimulation testing 1, 3

Common Pitfalls and Caveats

• Avoid relying solely on a single growth measurement; track growth over time using appropriate growth charts (WHO charts for children <2 years, CDC charts for children ≥2 years) 4
• Be aware that laboratory reference ranges vary by age, sex, and pubertal status 5
• Consider that growth failure may be the first sign of an underlying chronic condition before other symptoms appear 6
• Remember that nutritional causes are most common, but don't miss underlying pathology 2, 4
• Growth hormone testing should not be performed until other causes of growth failure have been ruled out 1, 3
• Ensure proper nutritional assessment before extensive laboratory evaluation, as inadequate caloric intake is the most common cause of growth failure 4

Follow-up Recommendations

• Laboratory tests should be interpreted in the context of clinical findings, growth patterns, and family history 5
• If initial laboratory evaluation is negative but growth failure persists, consider referral to pediatric subspecialists (endocrinology, gastroenterology, genetics) 1, 4
• Reassess growth parameters every 3-6 months depending on age and severity of growth failure 5