The inflammatory response is an important innate immune process that protects the body when tissues are injured by pathogens, trauma, toxic compounds, heat, etc. When it works properly, the acute inflammatory response quickly activates, complements, and promotes phagocytic activity, and then returns to a steady state, ready to respond when injury occurs again. This return to a low inflammatory state is vital for proper response. Even with simple vaccinations, a study found that “inflammation, even subclinical, can result in the development of an immunological risk group, in which vaccination fails to provide sufficient immunity.”1
It is generally recognized that the best marker for measuring the inflammatory response are the acute phase proteins. The major positive acute phase protein in dogs is C-reactive protein. CRP concentrations can increase 100-fold and rise quickly; typically, within 24 to 48 hours. Measuring CRP can be clinically useful in these situations:
• Screening the apparently healthy dog. By definition, a healthy dog should not have any inflammation, and if inflammation is present, it is likely to be chronic. Detecting inflammation in the “normal” dog may be an early sign of emerging occult disease. A high-sensitivity CRP test is necessary to screen for inflammation.
• Disease activity and progression. CRP is a useful tool to gauge disease activity in chronic enteropathies for dogs with GI disease,2 and is helpful for differentiating asymptomatic mitral valve disease (MVD) from congestive heart failure.3
• Therapy efficacy. CRP rises and falls rapidly. If a therapy is effective, the CRP should fall quickly, within two to four days. For instance, IMHA patients showing a positive response to therapy should see a rapid reduction in CRP. If medication is having a positive impact on IBD patients, their CRP should stay low.
CRP and albumin, independently, have long been used as markers for prognosis. Patients with either high inflammation or low albumin tend to have worse outcomes. Now, use of the C-reactive protein/albumin ratio (CAR) is growing in human medicine. Combining these two well-recognized, independent markers into a single metric can offer greater prognostic insight. High CAR values, where the body is in a high inflammatory state with low albumin, has demonstrated poor outcomes in cancer survival, post-surgical complications, sepsis mortality, and other serious disorders. New studies in canines show CAR to be a better metric than CRP or albumin alone for estimating length of hospital stay, time of recovery in a variety of serious diseases, and relative risk of death in dogs with acute pancreatitis.4,5
Canine CRP does not share common antigenicity with human CRP, so testing methods do matter.6 Many labs use a human CRP assay that does not recognize canine CRP consistently, leading to poor precision and low accuracy. A high-sensitivity canine-specific CRP assay is strongly recommended.
1 Povey RC. Distemper vaccination of dogs: factors which could cause vaccine failure. Can Vet J 1986;27(9):321-3.
2 Jergens AE, Schreiner CA, Frank DE, et al. A scoring index for disease activity in canine inflammatory bowel disease. J Vet Intern Med 2003;17(3):291-7.
3 Reimann MJ, Ljungvall I, Hillström A, et al. Increased serum C-reactive protein concentrations in dogs with congestive heart failure due to myxomatous mitral valve disease. Vet J 2016;209:113-8.
4 Gori E, Pierini A, Lippi I, Ceccherini G, Perondi F, Marchetti V. Evaluation of C-reactive protein/albumin ratio and its relationship with survival in dogs with acute pancreatitis. N Z Vet J 2020;68(6):345-348.
6 Fabretti K, Siqueira R, Amaral H, Kemper D, Chaves R, Pereira P. Determination of the reference interval of the C-reactive protein/albumin ratio and its efficiency, CRP and albumin as prognostic markers in dogs. Presq. Vet. Bras 2020;40(3):202-209.
6 Yamamoto S, Miyaji S, Abe N, Otabe K, Furukawa E, Naiki M. Canine C-reactive protein (CRP) does not share common antigenicity with human CRP. Vet Res Commun 1993;17(4):259-66.