Six hours? Two hours? One hour? McDonalds’ drive-thru?
This is the paper from Archives of Internal Medicine that’s been making the rounds in the lay press regarding how quickly the ER should be able to detect your AMI with the new highly-sensitive troponins. This is the APACE, prospective, international, multi-center study evaluating patients with “symptoms suggestive of acute myocardial infarction” and onset within the last 12 hours.
In this cohort, 1247 patients were recruited – and >300 were excluded for either going straight to the cath lab or having “another procedure performed” at the 1-hour time mark – and received hs-cTnT at index, 1, 2, 3, and 6 hours after presentation. Myocardial necrosis was defined as a hs-cTnT >99th percentile, which for this assay is 14 ng/L, and a diagnosis of acute MI was made by two independent cardiologists upon review of records and lab results.
The authors split their cohort into two groups, a derivation cohort and a validation cohort, and did some statistical wrangling to come up with two cut-off strategies – one for rule-in and one for rule-out. They were able to make diagnostic decisions on ~76% of their cohort at the one-hour time point, and 52 ng/L at presentation or an increase within an hour of 5 ng/L or more was ~94% specific for AMI. Likewise, 12 ng/L and an increase less than 3 ng/L at 1 hour was ~100% sensitive for AMI. The remaining 25% of their cohort was in a non-diagnostic zone. At 30 days, there was one death in their rule-out cohort, for a 99.8% survival rate.
So, can you use this strategy? If you feel as though this study is externally valid to your populations and you’re using the same Roche Diagnostics test, you certainly may. Every piece of data is something you can incorporate to your discussions with a patient regarding diagnostic certainty and risk. Even an extra hour occupying an ED bed rather than moving out to a chest pain observation facility can significantly impede ED flow, while observation admissions are costly and inconvenient to patients. The ideal strategy will depend on the capabilities of individual departments.
This study, along with the primary author, are sponsored in part by Abbott, Roche, and Siemens.
www.ncbi.nlm.nih.gov/pubmed/22892889