New evidence-based A1, A2, A3 alarm time zones for transferring thrombolysed patients to hyper-acute stroke units: faster is better

Thang S. Han*, Giosue Gulli, Brendan Affley, David Fluck, Christopher H. Fry, Christopher Barrett, Puneet Kakar, Sapna Sharma, Pankaj Sharma

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

4 Citations (Scopus)
182 Downloads (Pure)


Objectives: The National Institute of Health and Clinical Excellence and The Royal College of Physicians recommend transferring thrombolysed patients with stroke to a hyperacute stroke unit (HASU) within 4 h from hospital arrival (TArrival-HASU), but there is paucity of evidence to support this cut-off. We assessed if a shorter interval within this target threshold conferred a significant improvement in patient mortality. Design: We conducted a retrospective analysis of prospectively collected data from the Sentinel Stroke National Audit Programme. Setting: Four major UK hyperacute stroke centres between 2014 and 2016. Participants: A total of 183 men (median age = 75 years, IQR = 66–83) and 169 women (median age = 81 years, IQR = 72.5–88) admitted with acute ischaemic stroke. Main outcome measures: We evaluated TArrival-HASU in relation to inpatient mortality, adjusted for age, sex, co-morbidities, stroke severity, time between procedures, time and day on arrival. Results: There were 51 (14.5%) inpatient deaths. On ROC analysis, the AUC (area under the curve) was 61.1% (52.9–69.4%, p = 0.01) and the cut-off of TArrival-HASU where sensitivity equalled specificity was 2 h/15 min (intermediate range = 30 min to 3 h/15 min) for predicting mortality. On logistic regression, compared with the fastest TArrival-HASU group within 2 h/15 min, the slowest TArrival-HASU group beyond upper limit of intermediate range (≥ 3 h/15 min) had an increased risk of mortality: 5.6% vs. 19.6%, adjusted OR = 5.6 (95%CI:1.5–20.6, p = 0.010). Conclusions: We propose three new alarm time zones (A1, A2 and A3) to improve stroke survival: “A1 Zone” (TArrival-HASU < 2 h/15 min) indicates that a desirable target, “A2 Zone” (TArrival-HASU = 2 h/15 min to 3 h/15 min), indicates increasing risk and should not delay any further, and “A3 Zone” (TArrival-HASU ≥ 3 h/15 min) indicates high risk and should be avoided.

Original languageEnglish
Pages (from-to)1659-1665
Number of pages7
JournalNeurological Sciences
Issue number8
Early online date27 Apr 2019
Publication statusPublished - 1 Aug 2019


  • Evidence-based medicine
  • ROC curve analysis
  • ischaemic stroke
  • thrombolysis
  • tPA
  • ROC analysis
  • Stroke units
  • Thrombolysis
  • Ischaemic stroke

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