How is Polyarteritis nodosa diagnosed
Are any specific laboratory tests helpful in the diagnosis of Polyarteritis nodosa?
No, most tests are nonspecific and reflect the systemic inflammatory nature of this condition. Elevated erythrocyte sedimentation rate (ESR)/C-reactive protein (CRP), anemia, thrombocytosis, and diminished levels of albumin are usually present. Decreased complement levels are unusual. Hepatitis B surface antigen (HBsAg) is present in 10% to 50%, depending on the series. Patients with hepatitis B-associated PAN will also be hepatitis B envelope antigen (HBeAg) and HBV DNA-positive. ANCAs, rheumatoid factor (RF), antinuclear antibody (ANA), and cryoglobulins should be negative in classic primary PAN.
Diagnosis of PAN is often difficult. You should suspect PAN in any patient who presents with constitutional symptoms and multisystem involvement. Key clinical features suggestive of PAN include skin lesions (e.g., palpable purpura, livedo, necrotic lesions, infarct of the fingertips), peripheral neuropathy (most frequently mononeuritis multiplex), abdominal pain (mesenteric vasculitis), and hypertension with microscopic hematuria/proteinuria. Once you suspect PAN, biopsy of accessible tissues should determine the diagnosis. If clinically involved tissues are not amenable to biopsy, a visceral angiogram should be performed.
