A population-based cohort study in three phases in a sample of patients, aged 50 years and over, registered with three local general practices. Ethical approval for all phases of the study has been obtained from the North Staffordshire Local Research Ethics Committee.
Phase 1: Baseline two-stage mailed survey to recruit the cohort for the study
Phase 2: Three-year prospective follow-up of general practice medical records
Phase 3: Repeat mailed survey at three years
Phase 1 – Cohort recruitment
Three practices from the North Staffordshire Primary Care Research Consortium are to be recruited to the study and contact details of all adults aged 50 years and over will be taken from each practice list (n = 11309). In the United Kingdom (UK), about 98% of the population are registered with a general practitioner (GP) and so practice registers provide a convenient frame for sampling a local population . The samples obtained will then be checked by the GPs for exclusions (for example, severe psychiatric or terminal illness) prior to the mailing procedure.
The baseline phase of the study is a two-stage mailed survey. Firstly, the study population will be mailed a "Health Survey" questionnaire which collects information on several areas of life including socio-demographics, general health, physical function, participation, and bodily pain. Responders to this questionnaire who give permission to be re-contacted and who report experiencing, in the previous 12 months, a hand problem or pain in either their hands, hips, knees, or feet will be mailed a "Regional Pains Survey" questionnaire which focuses on these four regional sites. At each stage, questionnaires will be mailed with a letter from the GP practice and a study information leaflet, with reminders to be sent to non-responders after two and four weeks.
"Health Survey" questionnaire
Details of the information to be collected by the "Health Survey" questionnaire are presented in Table 1. On receipt by the Research Centre, the date of birth and gender information given on the questionnaire will be compared with that obtained from the general practice lists to ensure that the respondent is the intended participant.
Participants to this first stage (Phase 1) will be eligible to take part in the second mailing stage if they:
a) Consent to further contact by the Research Centre
b) Respond positively to at least one of the questions relating to regional sites (hands, hips, knees, or feet)
If respondents satisfy both of these criteria, they will be mailed the "Regional Pains Survey" questionnaire.
"Regional Pains Survey" questionnaire
Details of the information collected by the "Regional Pains Survey" questionnaire are presented in Table 2.
Phase 2: Follow-up using general practice medical records
All participants to Phase 1 who give permission for their GP records to be accessed will have their computerised medical records tagged by a member of the Centre's Health Informatics Specialist team. All consultations for the 12-month period prior to cohort recruitment and all consultations for the three-year period following recruitment will be identified. The three practices participating in this research are fully computerised and all practice staff enter a code for each contact. These codes are part of the READ classification of morbidity and event coding which is widely used in the National Health Service in the UK and can be mapped to the International Classification of Diseases. The practices undergo annual audits completed by the Centre's Health Informatics team to assess the quality and completeness of the data entry at the practices.
The practice-held information will provide the basic data for analysis of health care utilisation. This will include all consultations, medications, and referrals to other health care professionals both within primary care and on to secondary care. All sensitive data (name, contact details) will be removed from the medical records data and the consultation data will be linked to the survey data through the unique survey identifier.
Phase 3: Follow-up using repeat mailed survey
A follow-up survey, at three-years post-cohort recruitment, will be mailed to all those participants in the baseline phase who gave permission for re-contact. This questionnaire will focus on current problems and changes occurring since recruitment. Details of the information to be collected by this questionnaire are presented in Table 3.
The size of the sample chosen for this study reflects the need to ensure that a cohort of sufficient size is identified in Phase 1 to enable follow-up analysis to be adequately powered. The three participating practices have a total of 11309 registered patients who are suitable to take part in the study. From pilot work we have estimated that the response to the "Health Survey" questionnaire would be approximately 73% (n = 8300) and 70% of those completing this questionnaire (n = 5800) would give permission for re-contact and access to medical records. Moreover, of those who give permission for re-contact, 71% (n = 4100) will have hand problems or pain in at least one of the four specified pain regions and be mailed the "Regional Pains Survey" questionnaire, with an estimated 90% (n = 3700) who will complete it.
Three-year follow-up, in terms of survey and general practice data, will then be collected on those responders to the "Health Survey" who are alive and registered at the study practices at the time of follow-up and who gave permission for re-contact and access to medical records. Based on data from a recently conducted three-year follow-up survey in an older population (Jinks, personal communication) it is anticipated that 90% (n = 5220) of those who complete the "Health Questionnaire" will be alive and registered at the same study practices at the time of follow-up. Moreover, it is estimated that approximately 77% (n = 4000) will complete the follow-up survey.
The data collected in Phase 1 will be examined for cross-sectional relationships. The data collected in Phase 2 will be linked to Phase 1 data to determine predictors of consultation for joint pain sufferers. The data collected at Phase 3 will be linked to Phase 1 data to determine changes occurring between the two surveys.