What studies are recommended for post-COVID (Coronavirus Disease 2019) syndrome?

Recommended Studies for Post-COVID Syndrome

The recommended studies for post-COVID syndrome should be symptom-based, with basic laboratory tests for all patients and specialized testing based on predominant symptoms. 1

Initial Assessment for All Patients

Basic Laboratory Studies

• C-reactive protein (CRP)
• Complete blood count with differential (focusing on neutrophil count and lymphocyte count)
• Kidney function tests
• Liver function tests (AST, ALT)
• Thyroid function tests (if clinically suspected) 1

Additional Basic Tests

• Consider measuring:
  • Fibrinogen
  • Neutrophil/lymphocyte ratio (NLR)
  • Lactate dehydrogenase (LDH) 2, 3

Symptom-Based Testing Algorithm

For Cardiovascular Symptoms

If presenting with chest pain, palpitations, tachycardia, or lightheadedness:

1. First-line tests:

   • ECG
   • Cardiac biomarkers (troponin, CPK-MB, B-type natriuretic peptide)
   • Orthostatic vital signs 1

2. Second-line tests based on symptoms:

   • For tachycardia/exercise intolerance:

     • Active stand test (for POTS evaluation)
     • Autonomic testing
     • Cardiopulmonary exercise testing (CPET) 1

   • For chest pain:

     • Echocardiogram (for cardiomyopathy evaluation)
     • Stress test (for CAD evaluation)
     • Coronary CT angiography (CCTA) for higher-risk patients 1

For Respiratory Symptoms

If presenting with dyspnea, cough, or exertional shortness of breath:

1. First-line tests:

   • Chest X-ray
   • Pulmonary function tests (PFTs) with diffusion capacity 1

2. Second-line tests:

   • Chest CT (at 3-6 months) for patients with abnormal PFTs or persistent dyspnea
   • Cardiopulmonary exercise testing (CPET) to differentiate cardiac vs. pulmonary etiologies 1

For Neurological Symptoms

If presenting with cognitive impairment, headache, or sleep disorders:

1. Basic neurological assessment
2. Consider referral for specialized neuropsychological testing for persistent cognitive issues 1

Special Considerations

Timing of Testing

• For symptoms persisting >12 weeks: comprehensive evaluation is recommended
• For symptoms at 4-12 weeks: case-by-case assessment based on severity 4

Laboratory Findings Associated with Post-COVID Syndrome

Recent research indicates patients with post-COVID syndrome often show:

• Lower lymphocyte counts
• Higher neutrophil counts
• Higher fibrinogen levels
• CRP in the low-grade inflammation range (0.3-1.0 mg/dL) 2, 5

Common Pitfalls to Avoid

1. Overreliance on single tests: No single test can diagnose post-COVID syndrome; a comprehensive approach based on symptoms is necessary

2. Failure to exclude other conditions: Post-COVID syndrome is a diagnosis of exclusion; other conditions must be ruled out first 4

3. Unnecessary testing: Not all patients require extensive testing; tailor investigations to specific symptoms and their severity

4. Delayed rehabilitation: Do not wait for all test results before initiating rehabilitation, which is a primary recommended intervention 4

5. Missing sex-based differences: Women and men may present with different symptom patterns and inflammatory marker profiles in post-COVID syndrome 2

Remember that post-COVID syndrome management should focus on symptom-based supportive care, with physical and respiratory rehabilitation being the primary recommended interventions for improving outcomes related to morbidity, mortality, and quality of life 4.