medical emergency teams ( mets ) and critical care outreach are no longer new ideas . the services were founded in australia in the 1990s with the concept of mets using the well - recognised principle that early recognition and aggressive intervention improves outcome from critical illness . the systems have now developed into a variety of incarnations around the globe  becoming critical care outreach services ( ccos ) in the united kingdom , and the rapid response teams in north america [ 3 - 5 ] . although there are some differences between these services , they all have the same primary aim of preventing critical illness with its associated morbidity and mortality . ccos losing its youth produces an urgent requirement for efficacy and cost - effectiveness to be demonstrated . the most detailed evaluation to date of these systems is the merit study from australia , which was a multicentre cluster randomised trial of mets . sadly , the study failed to demonstrate a reduction in intensive care unit ( icu ) admissions , cardiac arrests or inhospital mortality . there are some weaknesses in the trial but it still represents by far the highest level of evidence to date on mets / ccos . the publication of this disappointing result led to a rapid distancing of ccos from their met parent , clearly fearing that this result would tarnish their new - found status . indeed , since the publication of the merit study , proponents of ccos have commonly stated that ccos can not be tested using a randomised controlled trial design , and some proponents seemed to believe that supportive evidence was not required at all . thankfully , in the previous issue of critical care a detailed evaluation of ccos in the united kingdom from a group based at the intensive care national audit & research centre in london was published . in the paper the authors restate the principle that ' ccos can not now be evaluated using the gold - standard research design , a multicentre , randomised controlled trial ' , and instead one must use an interrupted time - series method . the analysis was performed on the intensive care national audit & research centre case - mix programme ( a high - quality clinical database of nearly 400,000 icu admissions ) and on data taken from a large national survey of ccos . a range of outcomes designed to ' reflect the ccos objectives of averting admissions , ensuring timely admission and enabling discharge were investigated ' , including the proportion of admissions direct from wards , the length of icu stay , icu mortality and hospital mortality . sadly , despite reductions in cardiopulmonary resuscitation rates and physiological disturbance in the time before icu admission , ccos were not associated with an improvement in icu mortality or hospital mortality . further , the authors were unable to identify which of the many highly variable operational characteristics of the ccos were optimal . interestingly , they observed that there was no ' dose  response ' relationship for ccos that could have implied that the greater the ccos coverage , the better the outcomes that can be achieved . finally , the authors observed that ' ... changes in admission characteristics may be attributable in part to the use of physiological track and trigger warning systems ' , despite the fact that this group 's previous work demonstrated very poor sensitivity and specificity for such scores . so where does this leave us with regard to future of ccos in the united kingdom and beyond ? the continued inability of studies to demonstrate the efficacy of ccos and a complete lack of evidence for cost - effectiveness is worrying . a recent guideline by the national institute for health and clinical excellence on the management of the acutely ill hospital patient was unable to recommend outreach services due to a lack of supportive evidence . the national institute for health and clinical excellence did feel able to recommend the use of early warning scoring systems but was unable to identify a particular system or cutoff points due to the lack of evidence of accuracy for these scores in clinical practice . despite the lack of evidence , the institute of healthcare improvement recommends ' deploying rapid response teams ' as one of their 12 interventions ' proven to prevent morbidity and mortality ' in their 100,000 lives campaign . the institute of healthcare improvement clearly has access to an evidence base that the rest of us do not . do early warning systems actually allow early identification of sick patients , or are their diagnostic accuracies too low to justify use in clinical practice ? 2 . is there an optimal configuration for ccos that can actually lead to an improvement in important patient - based outcomes ? 3 . if ccos can be demonstrated to be efficacious will it prove to be cost - effective ? should countries that fund ccos now disinvest and spend these resources in more effective ways ? ccos = critical care outreach services ; icu = intensive care unit ; met = medical emergency team .
an evaluation of critical care outreach services was published in the previous issue of critical care that fails to demonstrate any important outcome benefit associated with these services . 
 it is now time to ask some difficult questions about the future of outreach , including whether the lack of evidence should lead to disinvest - ment in such services .