title: A review, and performance evaluation, of single-parameter "track and trigger" systems.
abstract: OBJECTIVE
  There is no up-to-date literature review of physiologically-based, single-parameter weighted "track and trigger" systems (SPTTS) and little data on their sensitivity and specificity to predict adverse outcomes. The aim of this study was to describe the SPTTS in clinical use and measure their sensitivity and specificity when using admission vital signs data for predicting in-hospital mortality.
  
  
  METHODS
  We performed a systematic review of the literature to describe the SPTTS, their components and their differences. We measured their sensitivity and specificity for predicting in-hospital mortality when using a database of 9987 admission vital signs datasets.
  
  
  RESULTS
  We identified 39 unique classes of SPTTS, of which 30 were evaluated. There was considerable variation in the physiological variables used, together with significant variation in the physiological values used to trigger a medical emergency or critical care outreach team. There was marked variation in sensitivity (7.3-52.8%), specificity (69.1-98.1%), positive predictive values (13.5-26.1%), negative predictive values (92.1-94.2%) and the potential number of calls triggered (234-3271).
  
  
  CONCLUSIONS
  There is a wide range of unique, but very similar, SPTTS in clinical use. Although specificities were high, sensitivities were too low to provide institutions with confidence that these SPTTS could identify patients at risk of in-hospital death using admission vital signs. Institutions may wish to consider these data when selecting which, if any, single-parameter track and trigger systems to introduce.
authors.affiliation: Portsmouth Hospitals NHS Trust and University of Bournemouth, United Kingdom. gary.smith@porthosp.nhs.uk
authors.forename: Gary B
authors.initials: GB
authors.lastname: Smith
authors.forename: David R
authors.initials: DR
authors.lastname: Prytherch
authors.forename: Paul E
authors.initials: PE
authors.lastname: Schmidt
authors.forename: Peter I
authors.initials: PI
authors.lastname: Featherstone
authors.forename: Bernie
authors.initials: B
authors.lastname: Higgins
mesh_terms: D003422:Critical Care / Q000379:methods*; D006305:Health Status Indicators; D017052:Hospital Mortality; D006801:Humans; D008991:Monitoring, Physiologic / Q000295:instrumentation / Q000379:methods*; D011237:Predictive Value of Tests; D018570:Risk Assessment / Q000379:methods*; D012680:Sensitivity and Specificity