C-reactive protein: A major acute phase protein in dogs

Kristiina Ruotsalo

Animal Health Laboratory, University of Guelph, Guelph, ON

AHL Newsletter 2024;28(4):30.

Acute-phase proteins are produced by the liver in response to tissue damage, and play a role in the innate immune response. The acute phase protein profile differs from species to species, with some proteins exhibiting the characteristics of a major acute phase reactant in one species, yet only negligible increases within another.

C-reactive protein (CRP) is a major acute phase protein in dogs. Increased hepatic production begins within 4 hours of a stimulatory event, leading to increased serum concentrations reflective of both protein production and peripheral catabolism. CRP is present in negligible amounts in healthy animals, but can increase rapidly and dramatically (up to 100-fold) following an inciting event; the magnitude of this increase is dependent upon the nature of the insult. Stimulatory events can include inflammation, infection, immune-mediated disease, neoplasia and trauma. Concentrations decrease rapidly with resolution of the underlying stimulus.

 CRP can complement CBC (complete blood count) and serum biochemistry findings. CRP will start to decrease earlier than neutrophil concentrations as inflammation or infection subsides in response to treatment, and can therefore be used to guide duration of therapy. CRP concentrations appear to be unaffected by hydrocortisone treatment in healthy dogs, thus CRP may be helpful in monitoring response to therapy in dogs receiving corticosteroids. Steroid therapy typically results in peripheral neutrophilia, thus reducing the clinical utility of the CBC. CRP has been shown to help differentiate bacterial versus other (e.g., eosinophilic, cardiogenic) causes of respiratory disease. Dogs with bacterial discospondylitis diagnosed by MRI exhibited markedly increased CRP concentrations, although pyrexia and leukocytosis were only variably present. Persistently increased concentrations of CRP in dogs with pancreatitis was associated with a poor clinical prognosis. CRP has been shown to be increased in dogs with mammary tumors, lymphoma, mast cell tumours, sarcomas, and metastatic neoplasia. However, the magnitude of CRP increase was not always correlated with tumour grade or burden. In dogs receiving therapy for lymphoma, remission status was best assessed by comparison to individual baseline CRP concentrations rather than to a CRP reference interval. It was suggested that the utility of CRP for the diagnosis and monitoring of malignancy may be enhanced by concurrent measurement of other markers of cellular proliferation.

The AHL Clinical Pathology laboratory now offers a canine specific CRP assay (test code: crp) which requires a minimum of 0.5 ml of serum. A preliminary study within our lab utilizing 36 clinically well dogs resulted in CRP concentrations from 0 mg/L to 14 mg/L, similar to those reported by others. Clinical usage of CRP within our laboratory setting is relatively new; however, evaluation of this acute phase protein may be helpful in those instances where inflammation or infection are clinically suspected but changes in the CBC and serum biochemistry profiles are equivocal, and for monitoring response to therapy.

References

1.Albarracin V, et al. Canine pancreas-specific lipase and CRP in dogs treated with anticonvulsants (phenobarbital and potassium bromide). Topics in Compan An Med. 2015;30:57-61.

2. Heilmann R, et al. High dose hydrocortisone treatment does not affect serum CRP concentrations in healthy dogs. Vet Sci 2023:10:620-627.

3. Malin K, Witkousla-Pilaszewicz O. CRP as a diagnostic marker in dogs: A review. Animals 2022:12:2888.

4.Oberholter S, Cook A. C-reactive protein in dogs: A review for the general practitioner. TVP 2023: July/August:105-110.

5.Saellstrom S, et al. Serum TK1 protein and C-reactive protein correlate to treatment response and predict survival in dogs with hematological malignancies. Res Vet Sci 2022;145:213-221.