The diagnosis of clinically important infections in dogs (as in sepsis ) is a complex condition that is difficult to define, diagnose and treat. It is a range of clinical conditions caused by the body's systemic response to an infection, which if it develops into severe sepsis is accompanied by single or multiple organ dysfunction or failure leading to death. An accurate diagnosis and rapid patient management is vital for good outcomes.

Tell me more about Sepsis

Detecting Infections
Today, the use of white blood cell (WBC ) count, left shift , and/or fever as indicators of infection is common in both veterinary and human medicine. Fever and WBC are easily obtained parameters and initiating antibiotic therapy is commonplace if these are elevated. However, these parameters are indicators of inflammation , NOT infection.

A review of medical records at UC Davis Veterinary Medical Teaching Hospital over a two year period¹ evaluated the medical conditions of patients with leukocytosis . They found that of patients presenting with leukocytosis 34% had immune-mediated disease , 32% infection, 22% neoplasia , and 12% non-infectious necrosis (which includes diseases like pancreatitis). This study demonstrates leukocytosis can be found in a wide variety of medical conditions, many of which are non-infectious.

In another study, when the WBC and left shift parameters were joined, the combined specificity for infections was only 0.69 making these parameters an ineffective diagnostic test , Fever was found to have no association whatsoever.² This further highlights that these are inflammatory, not infection criteria.

More precise methods of detecting infections involve culture of the suspected infectious site; however difficulty of obtaining suitable specimens from internal abscesses or organs and considerable time to culture (2-3 days) often makes culturing impractical.

Lastly, the treatment regimens of infectious vs. non-infectious conditions are considerably different. For the best outcomes, having the correct diagnosis is vital.

Biomarker: VDxI pCNP CANINE
VDxI pCNP CANINE measures NT-proCNP, the N-terminal peptide fragment of C-type natriuretic peptide (CNP), the active hormone. CNP is a member of the natriuretic peptide family that includes BNP. CNP is a vascular dilating hormone that is produced primarily by the vasculardilating hormone that is produced primarily by the vascular endothelium cells in response to an infectious process associated with inflammation. CNP has a very short half life and is cleaved in-vivo producing NT-proCNP. NT-proCNP has a much longer half life and makes for a better diagnostic assay.

Use of VDxI pCNP CANINE

VDxI pCNP has been found to be an effective diagnostic test for clinically important infections. pCNP aids in the detection of a clinically important infection and to differentiate it from similarly presenting non-infectious causes of inflammation.

Detection of Clinically Important Infections
In a major university study³, pCNP was able to detect clinically important infections from non-infectious inflammation as well as healthy dogs. pCNP had a specificity of 0.94 and a sensitivity of 0.82.

 Differential Diagnosis of Similarly Presenting Conditions

Inflammation is a nonspecific sign; ie, causes of inflammation can be either infectious or non-infectious.
Note how in septic peritonitis, a true infection, the dog presented with leukopenia and neutropenia. Often the findings of a low white count are observed as the body localizes the cells within the site of the infection. pCNP was positive.

In the case of pancreatitis, leukocytosis was found in spite of it being a non-infectious condition. pCNP was negative.

Diagnostic Algorithm
The use of pCNP is simple. If you have a distressed dog with nonspecific signs of inflammation (high or low WBC, left shift, fever, rapid breathing, or rapid heart rate) and the source of that inflammation is not obvious, use the VDxI pCNP test.

References

1. Lucroy, et. al,, "Clinical Outcome and Associated Diseases in Dogs with Leukocytosis and Neutrophilia", 1999

2. Hauptman, et. al., "Evaluation of the Sensitivity and Specificity of Diagnostic Criteria for Sepsis in Dogs", 1997

3. DeClue, et. al., "Serum NT pro-CNP Concentrations in Dogs with Sepsis, SIRS and Healthy Controls". Abstract presented at the International Veterinary Emergency and Critical Care Symposium, 2009.