What laboratory tests are recommended for a pediatric patient presenting with fatigue?

Laboratory Testing for Pediatric Fatigue

Initial Laboratory Panel

For a pediatric patient presenting with fatigue, begin with a focused initial laboratory panel including complete blood count with differential, comprehensive metabolic panel, thyroid-stimulating hormone (TSH), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP). 1

This targeted approach is supported by evidence showing that:

• Laboratory studies affect management in only 5% of fatigue cases, and extensive testing is rarely productive 2
• Most pediatric fatigue cases have no identifiable organic cause on laboratory evaluation 3, 4
• The minimal investigation should include urinalysis, complete blood count, smear, sedimentation rate, and chest X-ray only when clinically indicated 5

Severity-Based Testing Strategy

Mild Fatigue (Score 1-3 on 0-10 Scale)

• No immediate laboratory testing required 1, 6
• Provide education and lifestyle counseling, then reassess at follow-up 7, 6
• For children aged 5-6 years, use simplified "tired" vs "not tired" assessment 7, 1

Moderate Fatigue (Score 4-6 on 0-10 Scale)

• Proceed with the focused initial laboratory panel described above 1, 6
• Order additional testing only if history or physical examination reveals localizing symptoms 5

Severe Fatigue (Score 7-10 on 0-10 Scale)

• Obtain comprehensive laboratory evaluation immediately 6
• Consider urgent specialist referral if white blood cell count >20,000/mm³ or concerning features present 6

What NOT to Test

Avoid extensive laboratory panels and repeat testing when initial results are normal, as this approach is not evidence-based and rarely changes management. 2

Specifically avoid:

• Routine Epstein-Barr virus, cytomegalovirus, or toxoplasma serologies unless specific clinical suspicion exists 4
• Immunoglobulin levels without immunodeficiency symptoms 4
• Antinuclear antibodies without rheumatologic symptoms 4
• Repeat testing when initial screening is normal 2

Additional Targeted Testing Based on Clinical Findings

When Anemia is Identified

• Treat based on specific etiology (iron deficiency, B12 deficiency, etc.) 6
• This represents one of the few laboratory findings that directly impacts management 2

When Sleep Disturbance is Suspected

• Consider formal polysomnography if obstructive or central sleep apnea is suspected 1, 6
• Sleep disturbances are present in 30-75% of fatigued patients 6

When Neurologic Abnormalities are Present

• Brain MRI may be indicated for focal findings, muscle weakness, or abnormal reflexes 1
• This requires urgent specialist referral 6

Common Pitfalls to Avoid

• Do not order extensive imaging studies unless red flags are present 1
• Avoid "fishing expeditions" with broad laboratory panels when history and physical examination are unrevealing 8
• Do not overlook medication side effects as potential contributors before ordering extensive testing 1
• Remember that if a medical illness causes fatigue, it is usually evident on initial presentation 8

Follow-Up Testing Strategy

• Schedule regular follow-up visits rather than sporadic urgent appointments 2
• Reassess fatigue severity at each visit using the numeric scale 6
• If initial screening is normal, repeat testing is generally not indicated unless new symptoms develop 2
• Most pediatric patients show symptomatic improvement over time (65% resolution, 29% improvement in one cohort) 3