What is the workup for elevated Erythrocyte Sedimentation Rate (ESR)/C-Reactive Protein (CRP) with fevers?

From the Guidelines

The workup for elevated ESR/CRP with fevers should begin with a thorough history and physical examination, followed by targeted laboratory and imaging studies, as recommended by the Society of Critical Care Medicine and the Infectious Diseases Society of America 1. The initial evaluation should include complete blood count, comprehensive metabolic panel, urinalysis, and blood cultures (at least two sets from different sites) to identify potential sources of infection or inflammation.

• Additional tests should be guided by clinical suspicion, such as:
  • Chest X-ray to evaluate for pulmonary infections or other thoracic abnormalities 1
  • HIV testing to consider opportunistic infections
  • Specific tests for autoimmune conditions, such as ANA, RF, ANCA, if clinically suspected
  • Procalcitonin for bacterial infections, if sepsis is a concern
• Consider echocardiography if endocarditis is suspected, as recommended by the American Heart Association 1
• CT scans of chest, abdomen, and pelvis may be necessary to identify occult infections or malignancies, particularly if the patient has recently undergone thoracic, abdominal, or pelvic surgery 1
• For persistent unexplained fevers with elevated inflammatory markers, consider PET-CT scanning, as suggested by the Society of Critical Care Medicine and the Infectious Diseases Society of America 1
• Bone marrow biopsy may be indicated if hematologic malignancy is suspected
• Empiric antibiotics should be considered only if bacterial infection is strongly suspected or the patient appears septic, typically starting with broad-spectrum coverage, and narrowing therapy once culture results return 1

From the Research

Workup for Elevated ESR/CRP with Fevers

Elevated ESR (erythrocyte sedimentation rate) and CRP (C-reactive protein) levels can indicate inflammation in the body, which may be caused by various conditions, including infections, autoimmune disorders, or chronic diseases. The following steps can be taken to work up elevated ESR/CRP with fevers:

• Obtain a thorough medical history and perform a physical examination to identify potential causes of inflammation 2
• Order laboratory tests, such as complete blood count (CBC), blood cultures, and liver function tests, to help diagnose the underlying condition 3
• Consider imaging studies, such as X-rays or CT scans, to evaluate for potential sources of infection or inflammation 4
• Monitor ESR and CRP levels over time to assess the response to treatment and adjust the treatment plan as needed 5

Interpretation of ESR and CRP Results

When interpreting ESR and CRP results, it is essential to consider the following:

• ESR and CRP can be elevated in both acute and chronic inflammatory conditions 3
• Discordant results between ESR and CRP can occur, and the causes of these discrepancies should be investigated 5, 6
• Age, body mass index (BMI), and other factors can influence ESR and CRP levels, and these factors should be taken into account when interpreting results 6
• ESR and CRP should be used in combination with clinical history and physical examination to diagnose and monitor inflammatory conditions 2, 4

Potential Causes of Elevated ESR/CRP with Fevers

Potential causes of elevated ESR/CRP with fevers include:

• Infections, such as pneumonia or enteric fever 3
• Autoimmune disorders, such as rheumatoid arthritis or lupus 5
• Chronic diseases, such as diabetes or metabolic syndrome 6
• Other conditions, such as osteomyelitis or cancer 5