The Utility of Acute-Phase Proteins in the Assessment of Treatment Response in Dogs With Bacterial Pneumonia

Viitanen, S.J.; Lappalainen, A.K.; Christensen, M.B.; Sankari, S.; Rajamäki, M.M.

ion. Another limitation concerns the method used for CRP measurements. The upper detection limit for the assay used was 210 mg/L, and measurements exceeding this concentration were set at 211 mg/L. Doing so underestimated the increase in serum CRP, because it has been shown that serum CRP can increase markedly above 211 mg/L in dogs with aspiration pneumonia. 45 This approach will affect the interpretation of the CRP ratio during the recovery process. These limitations make the interpretation of the CRP ratio in our study less informative. One dog, which was euthanized because of refractory BP, had a biphasic CRP response pattern similar to that described in connection with poor prognosis in humans with CAP. 52 Regarding other variables, dogs with msBP were characterized by a more pronounced left shift and lymphopenia and were significantly more hypoxemic. Respiratory samples in dogs with msBP were characterized by significantly more pronounced neutrophilia, eosinopenia, and lymphopenia compared to dogs with lsBP. These variables therefore could be useful as early markers aiding in the identification of dogs with a more severe course of BP. Escherichia coli as a causative agent additionally was correlated with a more severe course of BP. Moreover, coagulation abnormalities were detected only in dogs with msBP caused by E. coli. These findings likely are due to endotoxin produced by E. coli, affecting hemodynamics, blood clotting, and cellular and humoral immunity. 53 A similar finding of increased disease severity has been described in E. coli-induced CAP. 54 Additionally, prolonged aPTT has been correlated with a worse prognosis in both humans and dogs with systemic inflammation or sepsis. 55, 56 Initial radiographic findings were consistent with previously reported findings in dogs with BP. 2, 3 The resolution of the alveolar lung pattern was followed during hospitalization and follow-up visits. However, because thoracic radiographs were not repeated daily, an exact time point for the resolution could not be determined. Alveolar infiltrates resolved relatively rapidly in our study (69% of dogs had cleared alveolar infiltrates by day 10) compared to studies of humans. Only 33% of human patients with CAP had clearance of radiographic Table 2 . Comparison of demographic, clinical, and respiratory cytology findings at presentation in dogs with less severe bacterial pneumonia (BP) (requiring <2 days of hospitalization, n = 10) and more severe BP (requiring >2 days of hospitalization, n = 9, including 2 mortalities). infiltrates at day 7 and 62% at day 28, and it also has been shown that radiographic normalization lags behind clinical cure as assessed by physicians. 57, 58 With CAP, current research has not been able to show benefits for routinely repeating thoracic radiographs after clinical recovery. [57] [58] [59] Repeating thoracic radiographs during and after hospitalization therefore is not recommended in patients with uncomplicated recovery. 27 Additional information gained by thoracic radiographs, especially after the clearance of alveolar infiltrates, was minimal in our study in dogs with otherwise satisfactory clinical recovery. Antimicrobial treatment currently is recommended for 3-6 weeks or 1-2 weeks beyond the resolution of radiographic changes. 1, 6, 7 Markedly shorter antimicrobial courses are used in CAP. Antibiotics are recommended for 7-10 days in cases of mild-to-moderate CAP, and the use of biomarkers has proved useful