Blood Tests

🧪 Blood Tests for FIP Evaluation

Blood testing is a fundamental component of evaluating cats suspected of having feline infectious peritonitis (FIP). While no single blood test can definitively diagnose FIP, characteristic laboratory patterns can strongly support clinical suspicion and guide further diagnostic steps.

Blood results should always be interpreted by a licensed veterinarian in combination with physical examination, imaging findings, and clinical history.

🔬 Complete Blood Count (CBC)

The Complete Blood Count evaluates red blood cells, white blood cells, and platelets.

Common findings associated with FIP may include:

• Anemia – Reduced red blood cell count, often non-regenerative

• Lymphopenia – Decreased lymphocyte count

• Neutrophilia – Elevated neutrophils due to inflammation

• Thrombocytopenia – Reduced platelet count (less common)

These changes reflect systemic inflammation and immune response.

🧫 Total Protein (TP) and Globulin

FIP commonly causes abnormal protein levels in the blood.

Typical patterns include:

• Elevated total protein

• Increased globulin concentration

• Normal or decreased albumin

High globulin levels are driven by immune system activation and chronic inflammation.

⚖️ Albumin-to-Globulin Ratio (A/G Ratio)

The A/G ratio is a valuable screening indicator in suspected FIP cases.

Interpretation guidance (approximate):

• A/G < 0.8 → Increased suspicion

• A/G < 0.6 → Stronger association with FIP

• A/G > 0.8 → FIP less likely, but not excluded

Low A/G ratio reflects disproportionate globulin elevation relative to albumin.

🧬 Liver and Kidney Parameters

FIP may affect multiple organs, including the liver and kidneys.

Commonly evaluated markers include:

• ALT, AST, ALP – Liver function

• BUN, Creatinine – Kidney function

• Bilirubin – May increase with inflammation or jaundice

Abnormalities may indicate organ involvement or secondary complications.

🧪 Inflammatory Markers (When Available)

Some clinics may measure inflammatory biomarkers.

Examples include:

• Serum Amyloid A (SAA)

• C-reactive protein (CRP)

Elevated levels suggest active inflammation but are not specific for FIP.

⚠️ Important Limitations

• Blood tests cannot confirm FIP on their own.

• Similar laboratory changes can occur with other infections, immune diseases, or cancers.

• Trends over time are often more informative than single measurements.

• Results must always be interpreted by a veterinarian.

🧭 When Blood Testing Is Most Useful

Blood testing is valuable for:

• Initial screening when FIP is suspected

• Monitoring disease progression or response trends

• Identifying organ involvement

• Supporting differential diagnosis

Additional testing such as imaging, fluid analysis, or PCR may be recommended.

📚 References

This content is based on information from:

• Cornell University College of Veterinary Medicine

• Merck Veterinary Manual

• VCA Animal Hospitals

• International Society of Feline Medicine (ISFM)

• American Association of Feline Practitioners (AAFP)