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Kansas State Veterinary Diagnostic Laboratory

What do Serology Results Mean?

When used correctly, serologic tests play an important role in determining the immune status or exposure of an animal to a particular disease.  However, since titer results vary depending on the laboratory and testing methodology as well as the history of the animal itself, there are no definitive answers as to what titer is considered protective against any given disease.      

*A single titer result does not differentiate between vaccine status and exposure*
Therefore, when being used as a tool to diagnose clinical disease, it is imperative to send paired samples (acute and convalescent) drawn approximately 2 weeks apart to monitor any significant changes in antibody titers. Generally, a 4 fold increase in titers between paired samples is a good indication of recent infection.                       

Listed below are some general guidelines to follow when interpreting results of serologic tests.  For more detailed information regarding a specific case, please contact KSVDL Clientcare at 866-512-5650.

Species

Test

Comments

**A titer result of <1:2 (SN) or <1:10 (HI) indicates no detectable antibody and is considered negative**

Bovine

Bovine viral diarrhea (BVD) Type 1 & Type 2 SN

Titer levels are dependent upon vaccination history, vaccine type, and case history.  For assistance in interpreting titers, please call KSVDL Clientcare at 866-512-5650

Infectious bovine rhinotracheitis (IBR) SN

Titer levels are dependent upon vaccination history, vaccine type, and case history.  For assistance in interpreting titers, please call KSVDL Clientcare at 866-512-5650

Bovine respiratory syncytial virus (BRSV) SN

Titer levels are dependent upon vaccination history, vaccine type, and case history.  For assistance in interpreting titers, please call KSVDL Clientcare at 866-512-5650

Bovine parainfluenza virus (PI3) SN

Titer levels are dependent upon vaccination history, vaccine type, and case history.  For assistance in interpreting titers, please call KSVDL Clientcare at 866-512-5650

 

 

 

Canine

Canine distemper virus (CDV) SN

A titer of >=1:32 is considered protective.

Canine parvovirus (CPV) HI

A titer of ≥1:80 is considered protective.

Infectious canine hepatitis (ICH) SN

A titer of >=1:32 is considered protective.

Canine Adenovirus Type 2 (CAV-2)

A titer of >=1:32 is considered protective.

 

 

 

Equine

Equine viral arteritis (EVA) SN

The USDA considers a titer of ≥1:4 to be positive. A result of <1:2 is equivalent to a negative @ 1:4 or 1:8 result.

Equine herpesvirus (EHV) Type 1 SN

A titer of >1:128 may indicate recent infection.

Equine Influenza (EIV) Type 2 (OH) strain HI

A titer of ≥1:320 may indicate recent infection.

Feline

Feline calicivirus (FCV) SN

A titer of ≥1:16 is considered protective.

Feline herpesvirus (FHV) SN

A titer of ≥1:16 is considered protective.

Feline panleukopenia (FPV) HI

A titer of ≥1:20 is considered protective.

Feline infectious peritonitis (FIP) IFA

A negative titer does not rule out FIP.  A positive titer only indicates prior exposure to a coronavirus, not necessarily one that may cause FIP. When paired with suggestive clinical signs, a titer of >=1:1600 is further indication of FIP involvement.

 

 

 

Porcine

Swine influenza virus (SIV) H1N1 & H3N2 strain HI

Titers  >1:40 indicate exposure.

Porcine parvovirus (PPV) HI

Vaccine titers are generally <1:256 so higher titers may indicate recent infection.

Porcine circovirus Type 2 (PCV2) Quantitative IFA

Titers >1:40 indicate exposure.

Porcine respiratory and reproductive and respiratory syndrome (PRRS) (NA/EURO) IFA

Titers >1:10 indicate exposure.