What Tests Are Needed to Diagnose Pleurisy?

When pleurisy is suspected, a comprehensive diagnostic approach is essential to identify the underlying cause and assess the severity of the condition. Physicians typically rely on a combination of clinical evaluations and specialized tests to confirm the diagnosis and determine the most effective treatment plan.

Common Diagnostic Procedures for Pleurisy

1. Temperature Monitoring

One of the initial steps in evaluating potential pleurisy involves monitoring body temperature over time. Fever can be a key indicator of inflammation or infection. Doctors observe whether the fever follows a pattern—such as being higher in the morning or evening—which may help differentiate between bacterial, viral, or chronic conditions like tuberculosis. Persistent or recurring fevers often prompt further investigation.

2. Blood Tests and Laboratory Analysis

Blood work is a fundamental component of the diagnostic process. A complete blood count (CBC) can reveal elevated white blood cell levels, signaling an active infection or inflammatory response. Additional markers such as C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) may also be measured to assess the extent of inflammation in the body. These tests help narrow down possible causes and guide next steps.

3. Imaging Studies: X-rays and CT Scans

Imaging plays a crucial role in diagnosing pleurisy. A standard chest X-ray is usually the first imaging test performed. It can detect fluid accumulation in the pleural space, known as pleural effusion, and show signs of lung infections that may have spread to the pleura. In more complex cases, a chest CT scan provides a more detailed view, allowing doctors to evaluate the exact location and volume of fluid, assess thickening of the pleura, and rule out other conditions such as tumors or pulmonary embolism.

4. Thoracentesis: Analyzing Pleural Fluid

If excess fluid is present in the pleural cavity, a procedure called thoracentesis may be performed. During this process, a thin needle is inserted into the chest to withdraw a sample of the fluid. This sample is then analyzed in the lab to determine if the effusion is caused by infection, heart failure, cancer, or autoimmune diseases. Testing includes cell count, protein and lactate dehydrogenase (LDH) levels, glucose concentration, and microbiological cultures.

5. Specialized Tests for Common Causes

Since certain conditions frequently lead to pleurisy, targeted testing is often necessary. For example, tuberculosis is a leading cause of pleural inflammation in many regions. To diagnose tuberculous pleuritis, physicians may perform a tuberculin skin test (Mantoux test), interferon-gamma release assays (IGRAs), or examine pleural fluid for acid-fast bacilli. In some cases, a pleural biopsy may be required to confirm the presence of granulomas typical of TB.

Other potential causes—such as pneumonia, lupus, or malignancy—are also considered during the diagnostic workup. Depending on clinical suspicion, additional tests like autoimmune panels or even a thoracoscopy might be recommended for a definitive diagnosis.

Early and accurate diagnosis of pleurisy is vital for timely treatment and preventing complications such as respiratory distress or long-term lung damage. By combining physical assessment with advanced diagnostics, healthcare providers can tailor interventions to each patient's specific needs.