Giant cell arteritis (GCA) is an uncommon but important medical condition. The arteries in the head and neck become inflamed, causing headache, pain and tenderness in the temples on the side of the head. GCA is a medical emergency. It requires rapid treatment with steroids because inflammation in the blood vessels supplying the eye can cause permanent blindness and/or stroke. Symptoms often come on suddenly over a few days. However, it is thought that there may be clues to the diagnosis in the months or even years before the person develops typical symptoms such as headache or loss of vision. Examples of possible clues to the early diagnosis are anaemia (low haemoglobin levels) and having high blood pressure. Identifying clues to the presence of GCA could lead to earlier diagnosis and treatment, which is an important step to prevent irreversible loss of sight or stroke. To find out whether a study to investigate the existence of such clues to the diagnosis of GCA is possible in CPRD, we first need to examine how blood pressure measurements and haemoglobin are recorded in primary care.
Diagnosing GCA can be difficult. The GP needs to spot the condition and then refer the patient to a rheumatologist in the hospital. They confirm the diagnosis and provide advice regarding further treatment. To make sure the record of GCA from the GP means the person does have GCA, we will compare the recording of a GCA diagnosis in primary care with diagnoses in the hospital record.
The incidence of giant cell arteritis (GCA) is 2.2 per 10,000 person-years in the UK. It is a medical emergency, and relapses are common, affecting around 50% of patients. Though the classical symptoms of GCA are often sudden in onset, it has been thought that there may be prodromal indicators prior to the diagnosis being made. Hypertension is one such potential indicator. It is often treated with antihypertensives in primary care for years before the symptoms of GCA manifest. The exact mechanisms behind the aetiopathogenesis of hypertension in the years preceding GCA diagnosis remain unclear. Low haemoglobin levels or anaemia at diagnosis have also been observed. Many of the early symptoms of GCA are non-specific, making the diagnosis difficult. GPs commonly identify suspected GCA, but guidelines recommend referring patients to secondary care for specialist evaluation and diagnostic confirmation by a rheumatologist. Referrals are also made to an ophthalmologist if patients present with new visual symptoms.
Prior to undertaking an epidemiological study to investigate whether prodromal indicators to the diagnosis of GCA exist before diagnosis, we wish to explore the feasibility of undertaking such a study in CPRD. We will estimate the positive predictive value of a suspected GCA diagnosis in CPRD compared with secondary care codes in HES Admitted Patient Care and Outpatients data. We will also determine the frequency of recording and timing of (1) blood pressure readings and haemoglobin measurements and (2) hypertension and anaemia diagnoses in people subsequently diagnosed with GCA.
Diagnosis of GCA in 1) primary and 2) secondary care data; systolic blood pressure values; hypertension diagnosis; haemoglobin level values; anaemia diagnosis
Nishita Padmanabhan - Chief Investigator - Keele University
Nishita Padmanabhan - Corresponding Applicant - Keele University
Christian Mallen - Collaborator - Keele University
Edward Roddy - Collaborator - Keele University
James Bailey - Collaborator - Keele University
Sara Muller - Collaborator - Keele University
Sarah Mackie - Collaborator - University of Leeds
Toby Helliwell - Collaborator - Keele University
HES Admitted Patient Care;HES Outpatient;Patient Level Index of Multiple Deprivation