Etanercept (Enbrel®, Pfizer) is a human tumour necrosis factor alpha (TNF-α) receptor fusion protein produced by recombinant DNA technology. It binds to TNF-α and prevents its interaction with cell surface receptors, thus interfering with the inflammatory cascade. In adults, etanercept can be used to treat active, moderate to severe rheumatoid arthritis, either in combination with methotrexate when the response to standard disease modifying antirheumatic drugs (DMARDs) is inadequate, or as monotherapy, if methotrexate cannot be tolerated or if the disease is severe, active and progressive. Anti-TNF therapies, such as etanercept can slow the rate of progression of joint damage, reduce symptoms such as joint pain, swelling and mobility and improve physical functioning. Etanercept is also used to treat other inflammatory conditions such as psoriasis, ankylosing spondylitis, psoriatic arthritis and juvenile idiopathic arthritis (JIA) in patients who have had an inadequate response to standard therapy. In adults, etanercept is administered as a subcutaneous injection, 50 mg once weekly or 25 mg twice weekly .
Observational data on patients treated with anti-TNF therapies for moderate to severe rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis and other rheumatologic indications are available from the British Society of Rheumatology Biologics Register (BSRBR, ). The register captures information recorded by Consultants on a patient's current and previous treatments, disease severity as assessed by American College of Rheumatology (ACR) criteria and current disease activity based on the disease activity score-28 (DAS-28) at baseline. A short form Consultant questionnaire is repeated annually with information collected on events of special interest. Patient-reported outcome data from the EuroQoL  and Health Assessment Questionnaire (HAQ, ) are collected at baseline and 6-monthly intervals.
Naturalistic research has become increasingly important in assessing the use of therapeutic interventions in clinical practice. Many factors other than those related to the properties of the intervention may influence how it works in a real-life setting, such as the beliefs and behaviour of patients, healthcare providers and general healthcare characteristics.
This evaluation was designed to collect naturalistic data directly from patients who have been prescribed etanercept for the first time using the PROBE methodology. PROBE has been developed as a self-reported data collection tool by Patients Direct and has been used to collect data in other therapy areas such as side effects following H1N1 and/or seasonal influenza vaccination and for a new product licensed for insomnia. It consists of a web-based system supplemented by telephone reporting for patients preferring this reporting mode. The methodology is relatively inexpensive to administer, allows data to be collected easily from specific target groups and can be tailored to suit different types of investigation. Furthermore, it allows the 'baseline' respondents to be contacted again to provide longitudinal follow-up information, thus enabling patient-reported outcomes on the effectiveness, healthcare experience, adverse events and persistence of etanercept treatment to be tracked.
Electronic collection of patient-reported outcome data using web-based technology is becoming an established way of gathering health data. However, patients who respond on the Internet may not be typical of the general population, potentially being younger, more educated and of a higher social class. By providing the alternative option of participating using a Freephone service, the PROBE methodology alleviates any problem that the elderly or other groups may have in accessing the Internet and allows a more representative population to be obtained, which is vital for reducing bias. Original data used to perform this analysis is provided in Additional file 1.
In this evaluation, the research methodology of PROBE differs from that of the BSRBR as it is entirely patient (or carer/parent) reported and has a wider scope. Post-baseline data were collected on a patient's healthcare experience measured through questions such as time between prescription and delivery of etanercept and quality of injection training, and there were additional quality of life measures.
The overall aims of the evaluation were:
To determine the baseline characteristics of patients prescribed etanercept
To evaluate the healthcare experience of patients prescribed etanercept by assessing the service provision from hospital specialists through to home care delivery and training.
To measure patient-reported outcomes including persistence with treatment, benefits of treatment and adverse events
In this manuscript, a full description of the PROBE methodology is given under "methods" below and the baseline data are reported. Data on the healthcare experience of patients prescribed etanercept and follow-up data will be reported in separate manuscripts.