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History of CORE

Phase I: from concept to CORE

1970s to 1990s

The origins of CORE lie in a slightly obscure but seminal chapter by Irene Waskow entitled Selection of a core battery, published in 1975 and that arose out a 1970 American Psychological Association scientific conference on psychotherapy change measures. Waskow proposed the idea that there was merit in devising a core outcome battery that could be adopted by most researchers and yet at the same time recognising that they could also supplement this ‘core’ component with additional measures which were of special interest to particular groups of researchers. Although this proposal attempted to balance practitioner-driven selection of measures with some commonality of measurement across studies, the idea was not taken on board for a variety of reasons. However, by the mid- 1990s, the issue of outcomes was increasingly coming to the fore and a further conference on selecting a core outcome battery was held in the US that resulted in a substantial text published in 1997 entitled Measuring Patient Changes in Mood, Anxiety, and Personality Disorders: Toward a Core Battery and edited by Hans Strupp, Len Horowitz & Michael Lambert.

1990s: The need for a core outcome measure

These initiatives provided the momentum in the UK for devising a core outcome measure that could be adopted widely by both practitioners and researchers. While a vision of a core outcome struck a chord with many people, it also provoked concern, much of it quite understandable, as some sensed the potential for restricting choice and standardizing procedures. Two particular strands of thought related to (a) people wanting to use their own measure, and (b) a degree of ambivalence towards the existing outcome measures that were available. Practitioners tended to use either ‘home grown’ instruments or rely on measures imported from the US that tended to focus predominantly on symptoms. In addition, such measures were proprietary instruments that carried purchase costs and a bar on adapting them for specific needs in the UK. Hence, there was a need for a short and ‘free’ outcome measure that could be used widely in the UK.

1994: The Mental Health Foundation Psychotherapy Research Initiative

In 1994, the Mental Health Foundation (MHF) funded a conference on Psychotherapy Research at Balliol College Oxford. One specific outcome of this event was a Psychotherapy Research Initiative funded by the MHF that set out to support research in three areas, one of which was the development of a core outcome battery. The MHF grant specification commissioned a self-report measure that would be copyleft, acceptable to service users and practitioners, and would cover subjective wellbeing, problems/symptoms, functioning, and risk to self or others. A team led by us won the commission and the work ultimately yielded a measure meeting that specification: the Clinical Outcomes in Routine Evaluation-Outcome Measure (CORE-OM).


1995-1998: Development and philosophy of CORE

  The CORE-OM was designed as a non-proprietary measure of psychological distress. Crucially, it was informed by feedback from practitioners as to what they saw as being important to include in a core outcome measure. The domains that emerged fitted well with the MHF’s commissioning specification that the measure should cover: subjective wellbeing, problems/symptoms, functioning, and risk to self or others and gave a huge amount of information about how best to choose and to word items. Empirical testing in the UK showed that the resulting free, user friendly, and pantheoretical outcome measure was sensitive to both low intensity and high intensity ranges of distress, tapped positive attributes as well as pathological symptoms, and could be used in both research and clinical settings. Since its development, the CORE-OM has been verified in a general population sample, large samples in primary care, in secondary care settings, and both primary and secondary settings, and with older adults.

Phase IIa: Implementing the CORE System in psychological therapy services and computerised support systems


1998-2001: Implementing CORE system

The CORE-OM and CORE System were launched at a national conference hosted in Leeds in 1998. Subsequently the CORE system was adopted by a large number of UK psychological therapy services, encouraged and supported by a spin-off company headed by John Mellor-Clark and supported initially by the University of Leeds Innovations (ULIS) Ltd.

2001-present: CORE-PC and CORE Net

  In 2001, John set up his own company – CORE Information Management Systems (CIMS) – and was joined by Alex Curtis Jenkins. CIMS supported the implementation and adoption of the CORE System in psychological therapy services through the development and release in 2002 of CORE-PC as an IT platform. At the same time, the existing Trustees – Michael Barkham, Chris Evans, and Frank Margison – were joined by Richard Evans. Richard’s charities, the Artemis Trust and the Counselling in Primary Care Trust, provided further funding for work on the CORE instruments and system. With the increasing dominance of the web, CIMS was able to complement the CORE-PC with a web-based platform, CORE Net. Such a web based client/server design was at the cutting edge of developments and CORE-Net came to supersede CORE-PC. This development provided practitioners with greatly enhanced tools for accessing and interrogating data regarding their patients. The focus of this strand of work centred on enhancing the quality of service at the level of individual practitioners as well as that of the whole service and then focused increasingly on monitoring of individual cases through session-by-session data collection.

Phase IIb: Developing a family of CORE derivatives and their translations

1998-2012: CORE derivatives

  Overlapping with Phase IIa was research activity to develop derivations of the CORE-OM (the parent measure) in order to meet specific needs either in terms of length of the measure or the patient population. The following list comprises the derivations and the approximate year they became available in practice (which often occurred sometime prior to the initial publication documenting the derivate version).

  • Short Forms A & B (1998): Two 18-item parallel versions developed at the same time as the CORE-OM and used in research settings
  • GP-CORE (2005): For use with student or general populations (no risk items)
  • CORE-10 (2007): An easy-to-use briefer version emphasising depression and anxiety and with a risk item
  • CORE-5 (2008): A thermometer that could be used in conversation
  • LD-CORE (2012): For people with learning disabilities
  • CORE-6D (2012): a scoring system based on six items within the CORE-OM which delivers health utility (QALY: Quality of Life Adjusted Years) scoring for UK populations.

As of 2015, no new derivative versions of CORE are planned or envisaged. Publications on all versions exist with the exception of the CORE-5 (in prep.) and the Short Forms (which are referred to in the 2001 and 2002 articles on the CORE-OM as well as in the 2010 chapter summarising the CORE measures).

1998-present: CORE translations

  The other major hallmark of Phase IIb has been the development of translations of the CORE-OM and all derivatives into in excess of 25 languages. These include the following languages for which translations are either completed or underway:

Albanian, Bosnian, British Sign Language (BSL), Bulgarian, Catalan, Croatian, Czech, Danish, Dutch, Farsi, Finnish, French, German, Greek, Gujarati, Icelandic, Italian, Kannada, Lithuanian, Norwegian (Bokmol), Portuguese, Portuguese (Brazilian), Punjabi, Romanian, Russian, Sami, Serbian, Spanish (Castellano), Spanish (Argentinian), Slovak, Slovene, Swedish, Turkish, Urdu, Welsh, Xhosa

Phase IIc: Building Practice Based Evidence (PBE) for the psychological therapies

Practice Based Evidence (PBE) and CORE

 One of the yields of the adoption of a common outcome measure and system was the opportunity to collate and analyse data across multiple services, thereby providing evidence on the psychological therapies from methods other than clinical trials. A series of four datasets collected in 2001, 2005, 2008, and 2008 were collated by CIMS and analysed by academics, yielding a series of articles in prestigious journals. The themes addressed include the following: psychometric properties of the CORE-OM, outcomes benchmarking, risk, waiting times, translating between CORE and BDI, the effectiveness of contrasting psychological therapies, the contribution of therapist effects, predicting outcomes, sudden gains, early patterns of change, therapy durations, dropout and deterioration.

Copies of many of the articles can be sourced by using links in Publications or by searching our individual pages on ResearchGate.

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