Diagnostic utility of cardiac troponin I in cats with hypertrophic cardiomyopathy

Abstract

BackgroundCardiac troponin I (cTnI) is useful for assessing hypertrophic cardiomyopathy (HCM) in cats.ObjectiveTo measure plasma cTnI concentrations in healthy cats and evaluate the clinical utility of cTnI in determining the severity of HCM.AnimalsClinically healthy cats (n = 88) and cats with HCM (n = 93).MethodsMulticenter prospective study. Cats with HCM, including hypertrophic obstructive cardiomyopathy at various stages, were diagnosed using echocardiography. Plasma cTnI concentrations were analyzed by a commercial laboratory. Receiver‐operating characteristic curve analysis was used to evaluate the accuracy of plasma cTnI concentrations to detect HCM.ResultsThe median cTnI concentration was 0.027 ng/mL (interquartile range, 0.012‐0.048 ng/mL) in healthy cats. Concentrations were significantly higher in diseased cats than in healthy controls, and concentrations were significantly higher in cats with heart failure than in asymptomatic cats. A plasma cTnI concentration of 0.163 ng/mL had a sensitivity of 62.0% and specificity of 100% when used to distinguish normal cats from asymptomatic HCM cats without left atrial dilatation. A cutoff of 0.234 ng/mL had high sensitivity (95.0%) and specificity (77.8%) for assessing heart failure. The areas under the receiver‐operating characteristic curves were 0.85 and 0.93, respectively.Conclusions and Clinical ImportanceIncreased cTnI concentrations reflect the severity of HCM. If other causes of cardiac injury are ruled out, plasma cTnI concentration may be useful for predicting the severity of HCM in cats.

Evaluation of a sensitive cardiac troponin I assay as a screening test for the diagnosis of hypertrophic cardiomyopathy in cats

“…A significant difference also was found between asymptomatic cats with severe HCM and those that were decompensated or compensated under treatment. These findings are similar to those previously reported in which a sensitive cTnI assay also was used . Only between cats with moderate HCM compared to cats with mild or severe HCM as well as between cats with severe HCM compared to cats with ATE did this difference not reach significance.…”

“…This cutoff also showed good discrimination between healthy and asymptomatic cats with HCM (sensitivity, 87.8%; specificity, 95.4%), but it should be kept in mind that the reported sensitivities and specificities only apply for cats in which comorbidities have been excluded. Our determined cutoff is lower than that previously reported . Similar to a previous study, we used the currently most sensitive cTnI assay with a detection limit of 0.006 ng/mL, whereas the lowest detection limits in other previous studies were 0.03 ng/ml and 0.2 ng/ml, respectively.…”

“…Additionally, only 16% of the healthy control cats in that study received an echocardiographic examination, whereas the other cats were regarded as healthy based on physical examination, potentially allowing a high number of false negatives. The difference between our cutoff and that determined in a previous study might be explained by the different grading system and exclusion criteria used in our study. Because impaired renal function, hyperthyroidism, and hypertension cause increases in cTnI, we excluded such cats from our study.…”

“…Cats were excluded if they had a serum T4 concentration >4.5 μg/dL. The remaining serum was frozen and stored at −80°C for a maximum of 20 months for later evaluations of cTnI using the currently most sensitive assay (ADVIA Centaur TnI‐Ultra, Siemens Healthcare Diagnostics Inc., Erlangen, Germany) by IDEXX laboratories (Ludwigsburg, Germany), which has been proven to be applicable in cats . All echocardiographic examinations were performed using an ultrasound unit (Vivid 7 Dimension, General Electric Medical System, Waukesha, Wisconsin) equipped with a 7.0 (3.5/6.9) MHz phased‐array transducer by a board‐certified cardiologist or a resident directly supervised by a cardiologist.…”

“…Some investigators state that cTnI only can be used to differentiate cats with moderate‐to‐severe HCM from healthy cats, thus rendering it less useful as a screening test . Recently a cutoff of 0.163 ng/mL has been proposed to distinguish healthy cats from cats with HCM without left atrial dilatation . However, because of a sensitivity of 62%, its value as a screening test remains unknown.…”