Data inputs

Data generated for 6021 Canadian VISION study patients informed the probabilities of the monitoring results. Since the VISION study did not include nonscreened patients, we estimated the number of detected and missed cases of MINS after standard care using the number of symptomatic MINS cases (assumed detected in standard care) and the number of asymptomatic MINS cases (assumed undetected in standard care). The VISION study did not collect information on clinical symptoms in patients without elevation of the troponin T level of 0.04 ng/mL or greater. We assumed the incidence of noncardiac chest pain (i.e., false-positive in the standard-care group) to be 1% and explored the impact of this assumption in sensitivity analysis. We opted for this very conservative estimate of false-positive health state to avoid any overestimation of the cost in the standard-care group. Table 1 summarizes the model parameters and their distributions.

Parameters and their distributions of the model of troponin T monitoring on the detection of myocardial injury after noncardiac surgery

MINS = myocardial injury after noncardiac surgery; NA = not applicable; SE = standard error; VISION = Vascular Events in Noncardiac Surgery Patients Cohort Evaluation.

The VISION study did not collect data on resource use except for coronary angiography. We estimated the cost of the 2 alternatives based on predefined diagnostic algorithms to confirm or exclude MINS in the case of elevated troponin T levels in screened patients or suggestive symptoms in the standard-care group. The algorithms included fourth-generation troponin T measurements as monitoring and as serial follow-up in the case of elevated troponin T or of clinical symptoms (triggered troponin T measurements), a cardiology consultation and follow-up visits, and serial electrocardiography and echocardiography for all patients with elevated troponin T levels. Canadian VISION data were the source for the probability of coronary angiography and for the probability that the troponin T level exceeded the upper limit of normal as late as on the last day of scheduled measurement, thus resulting in additional, triggered troponin T measurements in screened patients. The model did not include costs related to the noncardiac surgical procedure itself because these resource items were identical in the 2 alternatives.¹² Costs were inflated by the Canadian health care Consumer Price Index as necessary.