What laboratory tests should be ordered for a patient presenting with insomnia?

Laboratory Testing for Insomnia

Routine laboratory testing is not indicated for the evaluation of chronic insomnia unless there is clinical suspicion for comorbid disorders. 1

Initial Assessment Approach

The diagnosis of insomnia is primarily made through clinical evaluation rather than laboratory testing. According to the American Academy of Sleep Medicine (AASM) guidelines, the evaluation should include:

• A thorough sleep history
• Detailed medical, substance, and psychiatric history
• Physical and mental status examination 1

Essential Non-Laboratory Assessment Tools

1. Self-administered questionnaires:

   • General medical/psychiatric questionnaire to identify comorbid disorders
   • Epworth Sleepiness Scale to identify sleepiness and potential comorbid sleep disorders
   • Two-week sleep log to identify sleep-wake patterns and variability 1

2. Additional assessment instruments:

   • Measures of subjective sleep quality
   • Psychological assessment scales
   • Daytime function measures
   • Quality of life assessments 1

When Laboratory Testing Is Indicated

Laboratory tests should only be ordered when there is clinical suspicion of specific underlying conditions that may be causing or exacerbating insomnia. Consider testing in these scenarios:

Suspected Medical Conditions

When clinical evaluation suggests potential underlying medical causes, consider:

• Complete blood count (CBC) - to evaluate for infections, anemias, and malignancies
• Thyroid-stimulating hormone (TSH) - to assess for thyroid disorders
• Erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) - to screen for inflammatory conditions
• HIV testing - if risk factors present
• Tuberculosis testing (PPD or interferon-gamma release assay) - if clinically indicated 2

Specific Considerations

• Restless legs syndrome: Check ferritin levels (values <45-50 ng/mL indicate a treatable cause) 2
• Medication effects: Consider medication levels if relevant (e.g., theophylline levels)
• Substance use: Drug screening if substance use disorder is suspected 1, 3

Advanced Testing

• Polysomnography: Not indicated for routine evaluation of chronic insomnia 1

  Only indicated when:

  • Reasonable clinical suspicion of sleep apnea or movement disorders
  • Initial diagnosis is uncertain
  • Treatment fails (behavioral or pharmacologic)
  • Precipitous arousals occur with violent or injurious behavior 1

• Actigraphy: May be indicated to characterize circadian rhythm patterns or sleep disturbances, particularly in insomnia associated with depression 1

Common Pitfalls to Avoid

1. Overordering tests: Avoid ordering comprehensive laboratory panels without specific indications
2. Ignoring clinical context: Laboratory testing should follow logically from history and physical examination
3. Missing comorbidities: Remember that multiple primary and comorbid insomnia disorders may coexist 1
4. Overlooking medication effects: Many medications can cause or exacerbate insomnia, including beta-blockers, bronchodilators, corticosteroids, decongestants, diuretics, and many psychiatric medications 1

Summary Algorithm

1. Complete thorough sleep history and physical examination
2. Implement standard assessment tools (sleep logs, questionnaires)
3. Order laboratory tests only if clinical suspicion of specific underlying conditions
4. Consider polysomnography only for specific indications, not as routine screening
5. Address identified underlying causes with targeted treatment

Remember that insomnia is primarily diagnosed through clinical evaluation, and laboratory testing plays a supplementary role only when specific medical conditions are suspected.