Yet again, the insanity of the race to a zero-miss culture funds another chest pain discharge prediction rule. In fact, the most telling part of this paper is in the very end when they compare the chest pain admission rates of the Canadian hospitals in this article to the U.S. hospital - 18% and 20% in Canada compared to 96% in the U.S. (combined ED observation status and inpatient). The difference in those numbers is insane - and I'm sure people could easily debate which is the preferred side of those numbers to be on.
In any event, the study is a prospective, observational data-gathering study of 64 variables related to the presentation of chest pain - some of which are objective and some of which are historical. It's an interesting read - in part because the inter-observer kappa for a lot of the historical variables is so terrible they weren't even usable. After collecting all their data, they did 30-day telephone follow-up or vital records review to evaluate the combined endpoint of death, myocardial infarction, or revascularization.
Via the magic of recursive partitioning, a patient without new EKG changes, a negative initial troponin, no history of CAD, atypical pain, and age less than 40 years separated out 7.1% of their study population that had zero 30-day outcomes. Adding a second negative troponin six hours later for the 41-50 year group gives another 11.2% of patients that had zero outcomes. So, a facility that admits 96% of their patients could potentially reduce admissions - but it might have less utility in Canada.
I'd rather see a two-hour second troponin than a six-hour one; it might reduce sensitivity, but it's wholly impractical to tie up a bed in the ED for 6 hours for a patient you want to send home. And, like most of these articles, the combined endpoint of death, MI, and revascularization is irritating. Considering there were twice as many revascularizations as myocardial infarctions, there really ought to be more granularity in these sorts of studies with regard to the actual coronary lesions identified rather than simply lumping them into a combined endpoint.
"Development of a Clinical Prediction Rule for 30-Day Cardiac Events in Emergency Department Patients With Chest Pain and Possible Acute Coronary Syndrome"