Suspect my cat has FIP? Take you to understand the veterinarian's diagnostic thinking and examination process (extremely important: there is no simple method for definitive diagnosis!)

Comprehensive assessment process for veterinarians to diagnose FIP: collecting clues step by step

When faced with a suspected FIP case, 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 against certain treatments), etc.

2. Comprehensive physical examination (Physical Examination)

The veterinarian will conduct a very careful systemic 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 **eye examination** (FIP may cause intraocular inflammation) and necessary **neurological examination** (assessing for neurological symptoms).

3. Important blood tests (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 examination:** 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 in FIP, suggesting a strong chronic inflammation or immune response in the body. However, other chronic inflammatory diseases can also cause this.
  • **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) supports the diagnosis of FIPimportant clues, but it is also not absolutely specific.
  • **Bilirubin elevation:** If jaundice occurs, bilirubin will be elevated.
  • Other indicators: Assess 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 mutated viruses that cause FIP. A negative result cannot completely rule out FIP (especially in the later stages of the disease). Tashikin providesFIP Ab test stripsalso detects antibodies, and also has this limitation. The interpretation of the results must be extremely cautious,and must neverbe used as a diagnostic basis.[Learn about FIP Ab testing ]

4. Imaging (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 organ contours or enlargement, but the information is limited.
• **B-ultrasound:** For evaluating the abdomenextremely important. You can clearly see whether there isascites, evaluate whether themesenteric lymph nodesare enlarged (this is a relatively common feature of FIP), check whether there are abnormal lesions in the liver, spleen, kidneys and other organs (such as granulomas), and assess the thickness of the intestinal wall. It is especially valuable for the diagnosis of dry FIP.

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

If B-ultrasound or palpation reveals that the cat has pleural effusion or ascites (feline ascites testing), the veterinarian will usually take a small sample of fluid for analysis, which isvery helpfulfor the diagnosis of FIP:

• **Appearance and physical properties:** FIP exudate is usuallyyellow, viscous, clear or slightly turbid.
• **Rivalta's Test:** A simple and quick bedside test. 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, butrelatively low cell countto 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 usually also low.
• **FCoV RT-PCR test (for exudate):** Performing the RT-PCR test of FCoV inexudatesamples, ifa high viral RNA loadis detected, combined with typical liquid characteristics and clinical symptoms, it canstrongly 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 is used to screen for intestinal detoxification and isnot 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 the characteristic perivascular inflammatory lesions of FIP under a microscope, and detect feline coronavirus antigen in the macrophages of the lesion site by special staining methods such as immunohistochemistry (IHC) or immunofluorescence (IF). However, this method is usually difficult to implement safely on a living cat.

7. Summary: How does the veterinarian finally judge?

So,how does the veterinarian diagnose FIP? The answer is:There is no shortcut!Veterinarians must, like a puzzle, put togethermedical history, clinical symptoms, physical examination findings, blood test results (especially protein, A:G ratio, SAA and other patterns), imaging results, and the most valuable fluid analysis results (if there is ascites)and other clues meticulously, and conduct a comprehensive, meticulous, and exclusionary comprehensive assessment before finally reaching aclinical diagnosis(that is, highly suspected FIP based on existing evidence).