Physiological levels of C-reactive protein in normal canine sera

This study was undertaken to investigate whether the level of C-reactive protein (CRP) in the serum of dogs undergoes physiological variation, using 10 normal Beagle dogs (5 males and 5 females), 1-2 years old, maintained in a healthy condition in a controlled environment. The CRP concentration in the sera collected seven times each day at intervals of approximately 3 h ranged from 0.8 to 16.4 micrograms/ml (mean 5.06 +/- 3.60) in one experiment and from 0.8 to 14.0 micrograms/ml (mean 4.50 +/- 2.80) in a second experiment. On examining the 24-h variations in the concentration of CRP in serum, neither consistent changes nor a definite pattern of circadian rhythm was detected. During 28 days observation, only very slight changes, which seemed attributable to analytical errors, were seen in any of the dogs, except one. The concentration of CRP in the serum during the 28 days ranged from 0.8 to 22.6 micrograms/ml (mean 3.65 +/- 1.40). The concentrations underwent no significant variations in individual dogs, but significant differences were found between the dogs (p < 0.01).