What is the diagnostic workup for night sweats?

Diagnostic Workup for Night Sweats

The diagnostic workup for night sweats should begin with a thorough history focusing on B symptoms (fever, night sweats, weight loss >10% over 6 months), followed by targeted laboratory testing including complete blood count, ESR/CRP, liver function tests, and TSH, then appropriate imaging based on clinical suspicion, with chest X-ray as the initial imaging study for most patients.

Initial Assessment

History and Physical Examination

• Focus on specific characteristics of night sweats:
  • Frequency and severity (drenching vs. mild)
  • Duration of symptoms
  • Associated B symptoms (fever, unexplained weight loss >10% over 6 months) 1
  • Other associated symptoms: pruritus, fatigue, alcohol-induced pain 1
  • Sleep-related symptoms: daytime tiredness, waking with bitter taste, leg jerking, pain at night 2

Key Risk Factors to Assess

• Recent exposure to tuberculosis
• History of malignancy, particularly lymphoma or Hodgkin's disease 1
• Menopausal status in women
• Medication review (antihypertensives, antidepressants, antipyretics) 3
• Substance use (alcohol, heroin) 3
• HIV risk factors 1

Physical Examination Elements

• Comprehensive lymph node examination 1
• Assessment for hepatosplenomegaly 1
• Skin examination for rashes or lesions
• Vital signs, particularly noting fever and respiratory rate 1

Laboratory Testing

First-Line Laboratory Tests

• Complete blood count with differential 1, 4, 3
• Erythrocyte sedimentation rate (ESR) and/or C-reactive protein (CRP) 1, 3
• Liver function tests 1, 3
• Thyroid-stimulating hormone (TSH) 1, 4, 3
• HIV testing 1, 4, 3
• Tuberculosis testing (PPD or interferon-gamma release assay) 4, 3

Second-Line Laboratory Tests (Based on Clinical Suspicion)

• Lactate dehydrogenase (LDH) - particularly if lymphoma suspected 1
• Alkaline phosphatase - if bone metastases suspected 1
• Serum albumin 1
• Total IgE and IgG-anti-TPO levels - if autoimmune conditions suspected 1

Imaging Studies

Initial Imaging

• Chest X-ray - recommended as first-line imaging for most patients 4, 3

Advanced Imaging (Based on Clinical Suspicion)

• Contrast-enhanced CT scan of neck, chest, abdomen, and pelvis - if malignancy suspected 1
• PET/CT - particularly valuable for suspected lymphoma or Hodgkin's disease 1
• Bone scan - only if elevated alkaline phosphatase, bone pain, or radiographic findings suggestive of bone neoplasm 1

Special Considerations

When to Consider Bone Marrow Biopsy

• Abnormal complete blood count
• Suspected lymphoma with negative initial workup
• Unexplained persistent night sweats with constitutional symptoms 3

When to Consider Polysomnography

• Associated sleep disturbances
• Symptoms suggestive of obstructive sleep apnea 4, 2

Common Causes to Consider

1. Infections:

   • Tuberculosis
   • HIV
   • Endocarditis
   • Occult abscess

2. Malignancies:

   • Lymphoma
   • Hodgkin's disease 1
   • Leukemia
   • Metastatic solid tumors

3. Endocrine Disorders:

   • Hyperthyroidism 4, 3
   • Hypoglycemia 3

4. Other Common Causes:

   • Menopause
   • Medications (antidepressants, antihypertensives)
   • Gastroesophageal reflux disease 4, 3
   • Obstructive sleep apnea 4
   • Mood disorders 4

Clinical Pearls

• Night sweats alone do not indicate increased mortality risk 4
• If initial workup is negative and symptoms are not severe, a 4-8 week period of monitoring may be appropriate before pursuing more invasive testing 4
• Consider pulmonary embolism in post-surgical patients with new-onset night sweats, especially with pleuritic pain 5
• Night sweats are commonly associated with other sleep disturbances; consider sleep quality assessment 2

Algorithmic Approach

1. Initial evaluation: History, physical exam, first-line labs (CBC, ESR/CRP, LFTs, TSH, HIV, TB testing), chest X-ray
2. If suggestive of malignancy: Add LDH, proceed to CT imaging and consider PET/CT
3. If suggestive of infection: Add blood cultures, specific infectious disease testing
4. If suggestive of endocrine disorder: Add appropriate hormonal testing
5. If initial workup negative: Consider second-line testing based on persistent symptoms or clinical suspicion
6. If all testing negative: Reassurance and monitoring for 4-8 weeks 4

Remember that while night sweats can signal serious underlying conditions like lymphoma or tuberculosis, most patients with night sweats in primary care do not have a serious underlying disorder 4.