Developing methods for systematic reviewing in health services delivery and organization: an example from a review of access to health care for people with learning disabilities. Part 1. Identifying the literature.

OBJECTIVES: Our objectives were to identify literature on: (i) theory, evidence and gaps in knowledge relating to the help-seeking behaviour of people with learning disabilities and their carers; (ii) barriers experienced by people with learning disabilities in securing access to the full range of health services; (iii) interventions which improve access to health services by people with learning disabilities. DATA SOURCES: twenty-eight bibliographic databases, research registers, organizational websites or library catalogues; reference lists from identified studies; contact with experts; current awareness and contents alerting services in the area of learning disabilities. REVIEW
METHODS: Inclusion criteria were English language literature from 1980 onwards, relating to people with learning disabilities of any age and all study designs. The main criteria for assessment was relevance to the Guilliford et al. model of access to health care (Gulliford et al. Access to health care. Report of a Scoping Exercise for the National Co-ordinating Centre for NHS Service Delivery and Organisation R & D (NCCSDO). London: NCCSDO, 2001), which was modified to the special needs of people with learning disabilities. Inclusion criteria focused on relevance to the model with initial criteria revised in light of literature identified and comments from a consultation exercise with people with learning disabilities, family and paid carers and experts in the field. Data abstraction was completed independently and selected studies were evaluated for scientific rigour and the results synthesized.
RESULTS: In total, 2221 items were identified as potentially relevant and 82 studies fully evaluated.
CONCLUSIONS: The process of identifying relevant literature was characterized by a process of clarifying the concept under investigation and sensitive search techniques which led to an initial over-identification of non-relevant records from database searches. Thesaurus terms were of limited value, forcing a reliance on using free-text terms and alternative methods of identifying literature to supplement and improve the recall of the database searches. A key enabler in identifying relevant literature was the depth and breadth of knowledge built up by the reviewers whilst engaged in this process.