Suspect my cat has FIP? I'll take you through the veterinarian's diagnostic approach and examination process (extremely important: there is no simple method for definitive diagnosis!)

Comprehensive assessment process for veterinary diagnosis of FIP: collecting clues step by step

When faced with suspected FIP cases, veterinarians usually follow a rigorous logical process and comprehensively use various methods to evaluate: (not all of the following tests must be done, veterinarians will choose according to the specific situation)

1. Detailed medical history and basic information (Signalment & History)

This is a very important first step. The veterinarian will carefully ask: the cat's **age** (FIP is more common in young cats under 2 years old and old cats over 10 years old), **breed** (certain purebred cats are considered to be at slightly higher risk), **source** (whether it comes from a multi-cat environment such as a cattery or shelter), **living environment**, **vaccination and deworming history**, **symptoms** (when it started, how it developed, specific manifestations), **treatment response** (whether it is ineffective for certain treatments), etc.

2. Comprehensive physical examination

The veterinarian will perform a very careful full-body examination, including: measuring **body temperature** (whether there is a fever), assessing **weight** and body condition score, checking **mucosal color** (whether there is pallor or jaundice), palpating **lymph nodes** for enlargement, carefully **palpating the abdomen** (feeling for ascites, organ enlargement, or masses), **auscultating the heart and lungs**, performing a detailed **ophthalmic examination** (FIP may cause intraocular inflammation), and necessary **neurological examination** (assessing for neurological symptoms).

3. Important blood tests - provide clues, but cannot confirm the diagnosis

• **Complete blood count (CBC):** May find non-regenerative anemia, lymphopenia, and sometimes neutrophilia, which are non-specific manifestations of inflammation or chronic disease.
• **Serum biochemical tests:** This is a very important part, focusing on:
  • **Significantly elevated total protein (TP) and globulin (Globulin):** This is one of the most common hematological abnormalities of FIP, indicating a strong chronic inflammation or immune response in the body. However, other chronic inflammatory diseases may also cause it.
  • **Albumin levels may be reduced.**
  • **Significantly reduced albumin/globulin ratio (A:G Ratio):** A low A:G ratio (e.g., below 0.4 or 0.6, the specific critical value needs to be combined with the laboratory and literature) is supportive of FIP diagnosisimportant clue, but it is also not absolutely specific.
  • **Elevated bilirubin:** If jaundice occurs, bilirubin will be elevated.
  • Other indicators: Evaluate liver enzymes, kidney function indicators (BUN, Crea), etc. to see if other organs are involved.
• **Serum amyloid A (SAA):** SAA is a very sensitive acute inflammatory marker in cats. It is usuallysignificantly elevatedduring the active phase of FIP. Tashikin providesF. SAA test stripsto help veterinarians quickly assess inflammation levels.But please note: elevated SAA only indicates the presence of inflammation, and many other diseases can also cause it to rise. It itself cannot diagnose FIP. [Learn about F. SAA testing ]
• **Feline coronavirus antibody titer (FCoV Antibody Titer):**This test has very limited value for diagnosing FIP and may even be misleading!A positive result only indicates that the cat has been exposed to feline coronavirus (FCoV) in the past and cannot distinguish between harmless intestinal viruses and mutant viruses that cause FIP. A negative result cannot completely rule out FIP (especially in the late stages of the disease). Tashikin also providesFIP Ab test stripsto detect antibodies, which also has this limitation. The interpretation of the results must be extremely cautious,and must neverbe used as a basis for diagnosis.[Learn about FIP Ab testing ]

4. Imaging - looking for "clues" of lesions

• **X-ray:** Helpful for checking for fluid in the chest cavity (pleural effusion), heart size, and lung condition. Abdominal X-rays may show unclear or enlarged organ contours, but the information is limited.
• **Ultrasound:** For assessing the abdomenextremely important. You can clearly see if there isascites, evaluatemesenteric lymph nodesfor enlargement (this is a more common feature of FIP), check for abnormal lesions (such as granulomas) in the liver, spleen, kidneys, and other organs, and assess the thickness of the intestinal wall. It is especially valuable for the diagnosis of dry FIP.

5. Fluid analysis - If there is pleural or abdominal effusion, this is one of the most valuable tests!

If a veterinarian finds pleural or abdominal effusion in a cat through ultrasound or palpation (cat ascites test), they will usually draw a small amount of fluid sample for analysis, which isvery helpfulfor the diagnosis of FIP:

• **Appearance and physical properties:** FIP exudate is usuallyyellow, viscous, clear or slightly cloudy.
• **Rivalta's Test:** A simple and quick bedside test, in which a drop of exudate is dropped into a test tube of water containing a trace amount of acetic acid. If the droplet maintains its shape and sinks slowly (positive), it is highly suggestive of exudate (the possibility of FIP increases).
• **Biochemical indicators:** The liquid usually hasvery high protein content, butthe number of cells is relatively lowto the diagnosis of FIP.
• **Cytological examination:** The cells in the fluid are mainly macrophages and neutrophils, with fewer lymphocytes.
• **A:G ratio:** The A:G ratio in the exudate is also usually low.
• **FCoV RT-PCR test (for exudate):** Performing RT-PCR testing for FCoV inexudatesamples, ifa high viral RNA loadis detected, combined with typical fluid characteristics and clinical symptoms, it canvery strongly supportthe diagnosis of FIP.But please note that blood PCR testing for FIP is usually of little value.Tashikin providesFCOV Ag test stripsto detect antigens in feces, which are used to screen for intestinal detoxification and arenot directly relatedto the diagnosis of FIP.[Learn about FCOV Ag testing ]

6. Histopathology/immunohistochemistry - the "gold standard" for definitive diagnosis (but usually difficult to obtain ante-mortem)

The most reliable method for definitive diagnosis is to obtainsamples of diseased tissue(such as enlarged lymph nodes, lesions on the liver or kidneys) through surgery or autopsy, perform histopathological examination, observe FIP-characteristic perivascular inflammatory lesions under a microscope, and detect feline coronavirus antigen in macrophages in the lesions through special staining methods such as immunohistochemistry (IHC) or immunofluorescence (IF). However, this method is usually difficult to implement safely while the cat is alive.

7. Summary: How does the veterinarian finally judge?

So,how do veterinarians diagnose FIP? The answer is:There is no shortcut!Veterinarians must meticulously integrate all clues such asmedical history, clinical symptoms, physical examination findings, blood test results (especially patterns of protein, A:G ratio, SAA, etc.), imaging results, and the most valuable fluid analysis results (if there is ascites)together like a puzzle, and conduct a comprehensive, meticulous, and exclusionary comprehensive assessment to finally arrive at aclinical diagnosis(i.e., highly suspected FIP based on existing evidence).