From the Guidelines
The most appropriate test to order now is antineutrophil cytoplasmic antibodies (ANCA). This patient's presentation strongly suggests ANCA-associated vasculitis, particularly given his symptoms of shortness of breath, hemoptysis, fever, and abdominal pain in the context of hydralazine use, as noted in the evidence-based guideline for the diagnosis and management of eosinophilic granulomatosis with polyangiitis 1. Hydralazine is known to cause drug-induced vasculitis, which can present with pulmonary-renal syndrome. The laboratory findings of elevated creatinine, eosinophilia, and imaging showing bilateral opacities with centrilobular nodules further support this diagnosis. The nasal crusting may indicate upper airway involvement, which is common in granulomatosis with polyangiitis (formerly Wegener's granulomatosis).
According to the diagnostic work-up for EGPA, baseline investigations should include routine laboratory investigations, such as complete blood count with differential diagnosis, urinalysis, and immunological and/or allergic tests, including ANCA 1. While other tests, such as procalcitonin or plasma D-dimer, may have some utility, ANCA testing is most critical for diagnosing vasculitis in this clinical scenario, allowing for prompt initiation of appropriate immunosuppressive therapy and discontinuation of the offending medication. Early diagnosis is essential as untreated vasculitis can lead to progressive organ damage, particularly to the lungs and kidneys.
Some key points to consider in the diagnosis of EGPA include:
- The absence of diagnostic criteria, and the need for a diagnosis based on highly suggestive clinical features, objective evidence of vasculitis, and ANCA status 1
- The importance of considering asthma, chronic rhinosinusitis with polyps, eosinophilia, neuropathy, lung infiltrates, eosinophilic cardiomyopathy or gastroenteritis, and glomerulonephritis as highly evocative clinical features 1
- The use of classification criteria, such as the 1990 ACR or 2022 ACR–EULAR criteria, to support the diagnosis of EGPA, although these criteria should not be used as diagnostic criteria 1
Overall, the patient's presentation and laboratory findings suggest a high likelihood of ANCA-associated vasculitis, and ordering ANCA is the most appropriate next step.
From the Research
Diagnostic Considerations
The patient's symptoms, including shortness of breath, scant hemoptysis, fever, fatigue, and generalized abdominal pain, along with a history of asthma and hypertension, suggest a complex clinical presentation. The presence of eosinophilia (eosinophils 15) and the patient's recent history of asthma and corticosteroid use are particularly noteworthy.
Relevant Tests
Given the clinical presentation and laboratory findings, the following tests are considered relevant:
- Antineutrophil cytoplasmic antibodies (ANCA): This test is relevant due to the patient's symptoms and laboratory findings, which could suggest a diagnosis of eosinophilic granulomatosis with polyangiitis (EGPA), a condition characterized by asthma, eosinophilia, and vasculitis [ 2, 3, 4, 5, 6 ]. ANCA presence varies between 10 and 40% in EGPA patients [ 2 ].
- Other options, such as angiotensin-converting enzyme level, procalcitonin, and plasma D-dimer, may not be directly relevant to the primary diagnostic considerations based on the provided information.
Key Findings
- The patient's eosinophilia and history of asthma are key findings that align with EGPA [ 2, 3, 4, 5, 6 ].
- The presence of centrilobular nodules, bronchial wall thickening, and subpleural consolidations on CT angiography of the chest supports the consideration of EGPA or other pulmonary conditions [ 2, 3, 4 ].
Next Steps
Based on the clinical presentation and the evidence provided, ordering Antineutrophil cytoplasmic antibodies (ANCA) would be a logical next step to help diagnose or rule out EGPA and guide further management [ 2, 3, 4, 5, 6 ].