What laboratory tests and values are indicative of pericarditis?

Laboratory Tests for Pericarditis Diagnosis

The essential laboratory tests for diagnosing pericarditis include markers of inflammation (CRP and ESR), complete blood count with differential, cardiac biomarkers (troponins and CK), and renal and liver function tests. 1

First-Level Laboratory Tests (Required for All Cases)

• Inflammatory markers: C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are key indicators of inflammation in pericarditis 1, 2
• Complete blood count with differential: Helps assess for infection or inflammation; leukocytosis may be present 1, 2
• Cardiac biomarkers: Troponins and creatine kinase (CK) to detect myocardial involvement (myopericarditis) 1, 3
• Renal function tests: BUN, creatinine to evaluate kidney function and guide treatment 1, 2
• Liver function tests: To assess for systemic involvement or guide medication choices 1, 2
• Thyroid function tests: To rule out thyroid-related causes 1, 3

Diagnostic Values and Interpretation

• Elevated inflammatory markers: CRP and ESR are typically elevated in acute pericarditis, though normal values don't exclude the diagnosis, especially if the patient is already on anti-inflammatory treatment 2, 3
• Cardiac biomarkers: Elevated troponins suggest myocardial involvement (myopericarditis) rather than isolated pericarditis 2, 4
• White blood cell count: Leukocytosis may indicate infectious etiology 5, 6

Additional Tests Based on Clinical Suspicion

For Suspected Autoimmune Pericarditis

• ANA, ENA, ANCA tests 1, 2
• Ferritin if Still's disease is suspected 1
• ACE and 24-hour urinary calcium if sarcoidosis is suspected 1

For Suspected Tuberculous Pericarditis

• IGRA test (Quantiferon, ELISpot) 1, 2

For Suspected Viral Pericarditis

• PCR for viral genomes (preferred over serology) 1, 2
• Serology for HCV and HIV 1

For Suspected Bacterial Pericarditis

• Blood cultures (obtain before starting antibiotics) 1, 5
• Serology for specific pathogens if indicated (e.g., Coxiella for Q-fever, Borrelia for Lyme disease) 1

For Chronic Pericardial Effusion

• TSH and renal function tests 1

For Suspected Constrictive Pericarditis

• BNP (typically near-normal in constrictive pericarditis) 1

Pericardial Fluid Analysis (When Pericardiocentesis Performed)

• Cytology: Cell count and differential; higher volumes improve diagnostic yield 1
• Biochemistry: Protein and LDH (high values suggest exudate, though not validated for pericardial fluid) 1
• Microbiology: Aerobic and anaerobic cultures 1
• PCR for tuberculosis: When TB is suspected 1
• Adenosine deaminase: Values >40 U/L suggest tuberculosis 1
• Tumor markers: CEA >5 ng/ml or CYFRA 21-1 >100 ng/ml suggest malignancy 1

Common Pitfalls in Laboratory Interpretation

• Normal inflammatory markers don't exclude pericarditis, especially if the patient is already on anti-inflammatory treatment 2, 3
• Elevated cardiac biomarkers may indicate concomitant myocarditis rather than primary pericardial disease 2, 4
• Laboratory tests alone are insufficient for diagnosis; at least 2 of 4 diagnostic criteria (chest pain, pericardial rub, ECG changes, pericardial effusion) are required 3, 4
• Failure to obtain blood cultures before starting antibiotics can reduce diagnostic yield in suspected bacterial pericarditis 1, 5