Determination of Cardiac Troponin I in Guinea Pigs (Cavia porcellus) under Different Restraint Methods and Using a Point-of-Care Assay or Laboratory Analyzer.

Guinea pigs are a commonly used model for laboratory research, as well as being housed in zoological institutions and kept as pets. These animals can develop cardiac disease, and additional diagnostic modalities are needed to help expediently and accurately diagnose it. Cardiac troponin I (cTnI) is a cardiac-specific biomarker associated with myocyte damage. The objectives of this study were to (1) determine the utility of a point-of-care (POC) cTnI assay in guinea pigs via cardiac and skeletal muscle tissue homogenates serially diluted in saline; (2) compare this POC assay to a high-sensitivity assay; and (3) determine the effect of restraint method (awake, isoflurane, and ketamine-xylazine) on cTnI measurements. A total of 45 guinea pigs were used in this study. Homogenates of cardiac muscle produced detectable concentrations of cTnI, while skeletal muscle homogenates did not. There was a significant difference between the POC (cTnI median 0.000 [range 0.000-0.0450] ng/mL) and the high-sensitivity (cTnI 0.025 [range 0.010-0.042] ng/mL) assays, suggesting that the former may require its own reference interval. There were no significant differences detected among the order of treatments (P = 0.66320), the method of restraint (P = 0.2315), or the interaction between the treatments (P = 0.9755); however, there were more nonzero values obtained for cTnI 7 days after anesthesia with ketamine-xylazine. These results suggest that this POC assay may be useful in the detection of cTnI in guinea pigs using a variety of restraint methods, although a high-sensitivity assay is recommended when low concentrations or small variations in concentration need to be detected.