Assessment of a point-of-care cardiac troponin I test to differentiate cardiac from noncardiac causes of respiratory distress in dogs.

Objectives: To (1) determine a reference interval for cardiac troponin I (cTnI) using a point-of-care device in normal dogs and compare the results with those published by the manufacturer and (2) determine if cTnI differs among dogs with cardiogenic and noncardiogenic respiratory distress.

Design: Prospective observational study.

Setting: Emergency and referral veterinary hospital.

Animals: Twenty-six clinically normal dogs and 67 dogs in respiratory distress.

Interventions: All dogs underwent whole blood sampling for cTnI concentrations.

Measurements And Results: Normal dogs had a median cTnI concentration of 0.03 ng/mL (range 0-0.11 ng/mL). Thirty-six dogs were diagnosed with noncardiogenic respiratory distress with a median cTnI concentration of 0.14 ng/mL (range 0.01-4.31 ng/mL). Thirty-one dogs were diagnosed with cardiogenic respiratory distress with a median cTnI concentration of 1.74 ng/mL (range 0.05-17.1 ng/mL). A significant difference between cTnI concentrations in normal dogs and dogs with noncardiogenic respiratory distress was not detected. Significant differences in cTnI concentrations were found between normals versus cardiogenic and cardiogenic versus noncardiogenic respiratory distress groups. Significant differences in cTnI concentrations were identified in > 10 when compared with the < 5 and the 5-10 years of age groups. Receiver operating curve analysis identified cTnI concentrations > 1.5 ng/mL as the optimal "cut-off point" having a sensitivity of 78% and specificity of 51.5%. The area under the receiver operating curve was 0.72. Overall test accuracy was 65%.

Conclusions: cTnI concentrations were significantly increased in dogs with cardiogenic respiratory distress versus dogs with noncardiogenic respiratory distress and normal dogs. A significant difference between normal dogs and dogs with noncardiogenic causes of respiratory distress was detected. Although highly sensitive when cTnI concentrations exceed 1.5 ng/mL, the test has low specificity. Assessment of cTnI by the methodology used cannot be recommended as the sole diagnostic modality for evaluating the cause of respiratory distress in dogs.