Risk Stratification Cage Match & The Return of TIMI

Sending home chest pain has completely jumped the shark from frankly illegal to fashionably vogue.  Every day, another stick is shaken, and a mess of monkeys and new studies evaluating discharge strategies fall from the trees.

Today in the Octagon, five “established” risk scores for patients with acute coronary syndrome are pitted against each other in a prospective, observational study in Britain:  TIMI, GRACE, HEART, the Vancouver Chest Pain Rule (sure, OK), and the modified Goldman (???).  Each of these risk scores were paired with non-ischemic EKGs, and single initial blood samples for high-sensitivity troponin T (14 ng/L) and high-sensitivity troponin I (26.2 ng/L).  The authors’ stated goal: a negative predictive value of 99.5% for myocardial infarction within 30 days, and a capability of discharging at least 30% of patients at the initial presentation.

Oddly, it’s unexpectedly difficult to pick a winner.  The decision instrument with the greatest ability to discharge patients was TIMI ≤1, over 50% home from the ED, but it just barely missed the NPV threshold.  The modified Goldman ≤1, when paired with the troponin T, was capable of discharging 39.8% of patients with a sensitivity of 98.7%.  Then, the HEART score ≤3 was the most clinically acceptable when used with the troponin I assay, as it was the only decision-instrument taking into account small variations in serum troponin.  However, it just failed to meet the authors’ NPV threshold, as well.

So, what has changed since we last crowned HEART the new gnat’s pajamas?  Mostly the troponin assays, although this study also focuses more on NPV than sensitivity.  Indeed, a single hs-cTnT <14 ng/L had an NPV of 98.3% in this study, regardless of all other clinical features.  The implication, potentially, may be that the ideal risk-stratification decision-instrument can be designed for greater specificity, rather than sensitivity.  Other methods to increase sensitivity, such as paired troponins in certain situations, may allow for even further decision-instrument specificity, depending, of course, on the acceptable miss rate.

Despite its performance here, I’m not advocating for a return to TIMI – or to the modified Goldman – because I’m not quite so keen on their sensibility in the ED.  However, the interaction of HEART with different assays is intriguing, and perhaps a venue for further investigation and refinement.  It’s probably also worth mentioning an additional overlooked aspect – it is still OK to discharge a patient with a higher risk of AMI or death within 30 days if there is no additive survival benefit associated with acute hospitalization.

“Identifying Patients Suitable for Discharge After a Single-Presentation High-Sensitivity Troponin Result: A Comparison of Five Established Risk Scores and Two High-Sensitivity Assays”