What labs should be ordered for a patient presenting with night sweats?

Laboratory Evaluation for Night Sweats

Initial laboratory testing for patients presenting with night sweats should include complete blood count (CBC), thyroid-stimulating hormone (TSH), erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP), HIV testing, tuberculosis testing (PPD or interferon-gamma release assay), and chest radiography. 1

Initial Laboratory Workup

The following tests should be ordered as part of the initial evaluation:

1. Complete Blood Count (CBC)

   • Evaluates for hematologic malignancies, infections, and anemia
   • Abnormal findings may suggest lymphoma, leukemia, or infectious processes

2. Inflammatory Markers

   • ESR (Erythrocyte Sedimentation Rate) or CRP (C-reactive protein)
   • Elevated levels may indicate inflammation, infection, or malignancy

3. Thyroid Function Tests

   • TSH (Thyroid-Stimulating Hormone)
   • Evaluates for hyperthyroidism, which is a common cause of night sweats

4. Infectious Disease Screening

   • HIV testing
   • Tuberculosis testing (PPD or interferon-gamma release assay)

5. Basic Metabolic Panel

   • Electrolytes and renal function tests
   • Urine albumin:creatinine ratio to identify potential renal or endocrine disease 1

6. Chest Radiography

   • Evaluates for pulmonary infections, malignancies, or other chest pathologies

Additional Testing Based on Clinical Suspicion

If the initial workup is unrevealing or specific conditions are suspected, consider:

1. Advanced Imaging

   • CT scan of chest and/or abdomen if malignancy or infection is suspected 1

2. Specialized Testing

   • Polysomnography if sleep apnea is suspected
   • Bone marrow biopsy if hematologic malignancy is strongly suspected 1
   • Ferritin levels if restless legs syndrome is suspected (values <45-50 ng/mL indicate a treatable cause) 1

Clinical Context for Laboratory Evaluation

When evaluating night sweats, consider these common etiologies that may guide additional testing:

• Infections: TB, HIV, endocarditis, osteomyelitis
• Malignancies: Lymphoma, leukemia, other solid tumors
• Endocrine disorders: Hyperthyroidism, hypoglycemia, pheochromocytoma
• Sleep disorders: Sleep apnea, restless legs syndrome
• Gastroesophageal reflux disease (GERD)
• Medications: Antidepressants, antihypertensives, antipyretics

Important Clinical Considerations

• Night sweats alone do not indicate increased mortality risk in primary care patients 2
• If initial workup is negative and symptoms persist, consider referral to a sleep specialist, especially if the Epworth Sleepiness Scale score is ≥11 1
• Menopause and hyperthyroidism are among the most common hormonal causes of night sweats 3
• Consider medication review, as many drugs can cause night sweats including antidepressants, beta-blockers, and opioids 1

Follow-up Recommendations

• If initial testing is negative but symptoms persist, consider a systematic approach with additional testing
• If all testing is normal and no specific disorder is suspected, reassurance and continued monitoring are appropriate 2
• Direct treatment at the underlying cause when identified (e.g., anti-tuberculosis therapy for TB, acid suppression for GERD) 1

Remember that while serious causes like tuberculosis and lymphoma are classic associations with night sweats, in modern primary care practice, these are relatively infrequent causes compared to more common conditions like menopause, mood disorders, GERD, hyperthyroidism, and obesity 2.