Giant Cell Arteritis Patient Reported Outcome Measure (GCA-PRO)


The GCA-PRO is a validated outcome measure for use in clinical trials, observation studies and clinical practice. It can also be used as a communication tool between patients and their clinicians, to highlight areas of greatest importance to patients, within face to face or online consultations.


Giant cell arteritis (or GCA) is a condition that can cause pain and swelling in blood vessels. GCA affects arteries, which are the largest of the three types of blood vessels which take oxygenated blood from the heart to different parts of the body.

GCA is one of a group of conditions called vasculitis. The word vasculitis means inflammation in blood vessels. There are different types of vasculitis, because different blood vessels can be affected.

Giant cell arteritis (GCA) commonly presents in people over the age of 50 with cranial, ocular, and large vessel vasculitis and affects one or two persons per 10,000 people in the UK.

A 30-item GCA-specific patient reported outcome measure (GCA PRO) was developed and tested in a clinical setting to pilot its feasibility and acceptability to be used as a communication tool with patients.

Design and Development

The GCA-PRO was designed and developed by researchers at the Centre for Health and Clinical Research, University of the West of England, and Nuffield Department of Population Health (HSRU), University of Oxford, Oxford, UK.

The Outcome Measures in Rheumatology (OMERACT)
Large Vessel Vasculitis Working Group initially identified
the need for a disease-specific patient-reported outcome measure (PROM) for GCA. Generic PROMs, which can be used across a range of different diseases, may not always involve content specific enough for use in GCA.

A cross-sectional study was conducted to validate the GCA-PRO and included UK patients (n=428, mean age (SD) of 74.2 (7.2), 285 (67%) female) with clinician-confirmed GCA; diagnosed within the last three years or flaring within the last year. Patients completed the original 40 candidate GCA-PRO items, the EQ5D-5L, CAT-PROM5 and self-report of disease activity. Rasch and factor analysis were used to determine internal validity and factor structure. Item reductions were based on clinical importance, Rasch model fit, and redundancy. Tests of validity included comparison of the GCA-PRO (i) in participants with ‘active disease’ versus patients ‘in remission’ (known groups validity) and (ii) with EQ5D-5L and CAT-PROM5 scores (convergent validity).

After the initial analysis (40 items), ten items were deleted, and two response categories collapsed to ensure overall fit to the Rasch model. This resulted in a final PRO comprising a 30-item scale with a 4-response category structure. Factor analysis confirmed four factors (domains): Acute symptoms (8 items), Activities of daily living (7 items), Psychological (7 items) and Participation (8 items), all of which individually fitted the Rasch model (X2 = 25.219, DF=24, p=0.394 including reliability [Person Separation Index, PSI=0.828]), (construct validity). Each domain correlated, at least moderately, with EQ5D-5L and CAT-PROM5 scores (Spearman’s Correlation Coefficients 0.44 to 0.78) (convergent validity). The new GCA-PRO discriminated between patients with active disease and remission (known groups validity).

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Scoring System

The GCA-PRO is a patient reported self-administered questionnaire containing 30 statements which measure the symptoms and impact on health-related quality of life in patients with Giant Cell arteritis. The statements are grouped into 4 domains or “super-items” that measure specific aspects of the impact of disease.  A total GCA PRO score can also be calculated.

These domains are:

  • Acute symptoms (8 items)
  • Activities of Daily Living (7 items)
  • Psychological Impact (7 items)
  • Participation (8 items)

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Administration methods

The GCA-PRO is to date validated for pen and paper completion. Careful migration to a digital delivery format (for example screen based device) can be authorised. Please contact us for advice.

The GCA-PRO is designed to be completed by the patient unaided. Some patients may have ocular involvement so may require help with completing the PRO, in this case questions and responses may be read out loud by an assistant, and the patient’s answer recorded by the assistant.

Patients are asked to put a tick in the box next to the response that represents the frequency or severity of symptoms from GCA and its treatment, and impact on health-related quality of life in the previous 7 days. Only one box should be ticked for each statement.

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Associated Measures

You may also be interested in the following PROs developed by the same team:

  • AAV-PRO. The AAV-PRO is a new 29-item, disease-specific PRO measure for ANCA-associated vasculitis and used to assess the health-related quality of life and disease burden experienced by patients.
  • Steroid PRO. The Steroid PRO is the first validated and reliable patient-reported outcome measure designed to assess the impact of glucocorticoid-specific therapy on patients’ well-being and quality of life.

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