In a 67‑year‑old patient with a chronic non‑resolving cough and a history of prior lung injury, whose chest radiograph shows unchanged bilateral peribronchial interstitial fibrotic changes consistent with post‑acute lung injury and no mediastinal enlargement, what are the appropriate next diagnostic and therapeutic steps?

Diagnostic and Therapeutic Approach

Proceed immediately to high-resolution CT (HRCT) of the chest to definitively characterize the bilateral peribronchial interstitial fibrotic changes and establish a specific diagnosis, as plain radiography has insufficient sensitivity to guide management in suspected interstitial lung disease. 1, 2

Why HRCT is Essential Now

The chest X-ray findings of "bilateral peribronchial interstitial fibrotic changes" and "post acute lung injury" are descriptive but non-specific, and plain radiography has poor sensitivity (approximately 64-79% negative predictive value) for detecting the specific patterns needed to guide treatment decisions in interstitial lung disease. 2, 3

Key clinical features mandating HRCT in this patient:

• Chronic non-resolving cough in a 67-year-old with established radiographic abnormalities represents objective evidence of parenchymal disease requiring specific diagnosis before empiric treatment. 1, 2
• History of prior lung injury with persistent fibrotic changes raises concern for progressive fibrotic interstitial lung disease, which now has disease-modifying antifibrotic therapies available. 4
• Unchanged findings on serial imaging does not exclude progressive disease, as some fibrotic patterns (particularly nonspecific interstitial pneumonia evolving to usual interstitial pneumonia) may appear stable on chest X-ray while progressing on HRCT. 4

What HRCT Will Determine

The HRCT will differentiate between critical diagnostic possibilities that have vastly different prognoses and treatments:

Patterns with better prognosis (70-85% 10-year survival):

• Nonspecific interstitial pneumonia (NSIP) - responds to corticosteroids, 15-20% 5-year mortality 5
• Respiratory bronchiolitis-associated ILD (smoking-related) - improves with smoking cessation 5
• Organizing pneumonia patterns 5

Patterns with worse prognosis requiring antifibrotic therapy:

• Usual interstitial pneumonia/idiopathic pulmonary fibrosis - now treatable with antifibrotics 4
• Chronic hypersensitivity pneumonitis with fibrosis - categorized as fibrotic vs. non-fibrotic based on HRCT 4
• Mixed patterns (UIP with additional bronchiolocentric fibrosis) suggesting connective tissue disease or occupational exposure 5

HRCT can establish diagnosis without biopsy in most cases, avoiding invasive procedures. 1

Technical Specifications for HRCT

Request 1.5mm thin-slice HRCT to optimize resolution of interstitial patterns. 1

Concurrent Diagnostic Workup While Awaiting HRCT

Obtain detailed exposure history:

• Smoking status (current pack-years and cessation date) - respiratory bronchiolitis requires active smoking 5
• Occupational exposures (asbestos, silica, metal dusts, organic antigens) - peribronchial distribution suggests possible hypersensitivity pneumonitis or pneumoconiosis 5, 1
• Medication history - drug-induced ILD can present with NSIP pattern 5
• Bird/mold exposure for hypersensitivity pneumonitis 4

Assess for connective tissue disease features:

• Joint symptoms, Raynaud's phenomenon, skin changes, dry eyes/mouth 5
• Serologic testing: ANA, RF, anti-CCP, myositis panel if clinical suspicion exists 5

Pulmonary function testing:

• Spirometry with lung volumes and diffusing capacity (DLCO) 6
• Establishes baseline for monitoring progression 6
• Restrictive pattern with reduced DLCO supports fibrotic ILD 6

Quantify cough severity:

• Use validated cough severity scale - cough severity independently predicts disease progression, quality of life, and survival in fibrotic ILD 6
• Worse cough correlates with larger annualized decline in DLCO and reduced transplant-free survival 6

Screen for gastroesophageal reflux disease (GERD):

• GERD is strongly associated with worse cough in both IPF and non-IPF fibrotic ILD 6
• Treatment may improve cough symptoms 2

Common Pitfalls to Avoid

Do not assume "unchanged" radiographic findings mean stable disease. Fibrotic ILD can progress functionally and symptomatically despite stable-appearing chest X-rays, and NSIP patterns can evolve into UIP over time. 4

Do not delay HRCT in favor of empiric treatment trials when objective findings (abnormal chest X-ray, chronic cough, history of lung injury) indicate established parenchymal disease. 1

Do not proceed to transbronchial biopsy before HRCT, as characteristic HRCT patterns establish diagnosis without tissue in the majority of cases. 1

Do not dismiss peribronchial fibrotic changes as "just post-inflammatory scarring" without excluding active fibrotic ILD, as early diagnosis now enables antifibrotic therapy that slows progression. 4

In elderly patients, do not attribute all radiographic abnormalities to age-related changes - while up to 20% of patients over 70 have incidental bronchiectasis, symptomatic chronic cough with bilateral interstitial changes requires investigation. 2

After HRCT Results

If HRCT shows definite UIP pattern: Consider antifibrotic therapy (pirfenidone or nintedanib) as these are now approved for progressive fibrotic ILD beyond just IPF. 4

If HRCT shows NSIP or inflammatory patterns: Corticosteroid trial may be appropriate, with significantly better prognosis than UIP. 5

If HRCT shows hypersensitivity pneumonitis: Categorize as fibrotic vs. non-fibrotic (not acute/subacute/chronic), as prognosis depends on presence of fibrosis; antigen avoidance is critical. 4

If HRCT is indeterminate or shows unclassifiable pattern: Multidisciplinary discussion (pulmonologist, radiologist, pathologist) determines need for surgical lung biopsy. 5

Review any prior imaging if available - comparison increases diagnostic accuracy, particularly if current HRCT appears to show UIP but earlier studies showed NSIP features. 4