External validation of a stepwise 0/1/3h algorithm to triage patients with suspected myocardial infarction
Authors: Lehmacher J , Guo L , Toprak B , Soerensen N A , Haller P M , Schock A , Scharlemann L , Thiessen N , Zeller T , Neumann J T , Twerenbold R 
Published: October 2024

Abstract

Background
In patients with suspected myocardial infarction (MI), application of 0/1h-algorithms is recommended by guidelines of the European Society of Cardiology. Depending on assay-specific changes of high-sensitivity troponin (hs-Tn), these algorithms allow for rule-in or rule-out of MI at presentation or after 1 hour (h). Yet, a relevant proportion of patients remain in the observe group at 1h in need for further diagnostic. Recently, specific cutoffs at 3h were suggested for hs-TnT, enabling an additional 3h triage option in conjunction with the 0/1h algorithm to further reduce the proportion of patients in the observe zone.

Objective
We aimed to externally validate the diagnostic performance of the 0/1/3h algorithm in patients with suspected MI.

Methods
We consecutively enrolled patients with symptoms suggestive of MI in the emergency department of a tertiary hospital in Germany. Patients with STEMI were excluded. Concentrations of hs-TnT were measured at presentation, after 1h and 3h. Final diagnoses were adjudicated by two cardiologists according to the 4th Universal Definition of MI. Applying the 0/1/3h algorithm, patients were triaged into rule-in, rule-out- and observe-group. We assessed the diagnostic performance parameters in the overall sample as well as for predefined subgroups including sex, age ≥65 vs. &lt;65 years, glomerular filtration rate (GFR) ≥60ml/min/m² vs. &lt;60ml/min/m², and symptom onset time &lt;1h vs. 1-3h vs. &gt;3h).

Results
In 2,514 patients (median age 64 years, 36.4% female), prevalence of NSTEMI was 14.4%. Application of the 0/1/3h algorithm ruled-out 1511 (60.1%) and ruled-in 587 (23.3%) patients. Only 416 (16.6%) remained in the observe group at 3h. Safety of rule-out was high with a sensitivity of 98.6% (95%CI 96.8%, 99.4%) and a corresponding negative predictive value of 99.7% (95%CI 99.2%, 99.9%). Rule-in performance was acceptable with a specificity of 89.3% (95%CI 87.9%, 90.5%) and positive predictive value (PPV) of 60.8% (95%CI 56.8, 64.7, Figure 1). Regarding subgroup analyses, sensitivity and NPV were marginally but statistically lower in patients with normal as compared with impaired renal function (p both &lt;0.001). Further, specificity was substantially lower in older patients (84.8% vs. 93.3%, p&lt;0.001), patients with GFR&lt;60ml/min/m² (78.3% vs. 93.0%, p&lt;0.001) as well as in male patients (88.1% vs. 91.2%, p=0.028) (Figure 2). A relevantly larger proportion of patients remained in the observe group after 3h in patients with impaired renal function (32.3% vs. 10.9%), as well as in patients aged ≥ 65 years (26.8% vs. 6.8%).

Conclusion
Application of the 0/1/3h algorithm in patients with suspected MI resulted in good diagnostic performance with excellent rule-out safety and moderate rule-in capacity. In patients with impaired renal function as well as elderly patients, specificity was significantly lower while observing a larger proportion of patients remaining in the observe zone at three hours.Figure 1:Diagnostic flowFigure 2:Forest Plots