This study of incident PMR cases suggests that classical GCA symptoms are common in newly diagnosed PMR patients, with 1 in 4 patients reporting sudden headache, appetite loss or unintentional weight loss. Jaw pain on chewing was the least common reported symptom. Except for unintentional weight loss, a higher proportion of females reported all symptoms, whilst sudden headache, double vision and fever were reported by fewer people at older ages. Given that older patients seem to be at greater risk of both developing GCA and of visual loss (7) it may be that reporting of these symptoms is more specific in older individuals, who may report fewer symptoms but be at greater risk of complications. The most common combination of symptoms was headache with tender scalp and headache with double vision, each affecting approximately 10% of the cohort at diagnosis. Further follow up of the cohort will determine the proportion of patients who were formally diagnosed as having GCA.
The PMR Cohort study is the first inception cohort study of PMR patients in primary care and is of a substantial size. Although primary care recruitment can be seen as a weakness, because no specialist opinion as to the diagnosis was sought, this is also a major strength of the study because the majority of patients with PMR are diagnosed and managed exclusively in primary care [12]. This sample is therefore free of the potential spectrum bias that is likely to be present in studies conducted in specialist settings where disease may be more severe, atypical or difficult to manage. Reassuringly however, the demographic and clinical characteristics of this cohort are similar to other secondary care cohorts [13], providing confidence in the accuracy of the primary care PMR diagnosis. Furthermore symptoms were recorded from patients close to the time of diagnosis thus reducing the recall bias.
One of the limitations of this study is that at this stage it is unknown if the patient was formally diagnosed with GCA or not. The prevalence of possible GCA symptoms was higher in women in our cohort, in common with the reported higher prevalence of GCA in women. [7]. Furthermore, the study demonstrates that in patients with PMR, headache is a much commoner symptom than in the older adult general population. Work by Steiner et al. [14] demonstrated that in the older adult general population (aged 50–65) the prevalence of headache was 3.4% for males and 13.5% for females The prevalence of headache was considerably higher in our cohort (males 15.4%, females 30.4%), suggesting that PMR is associated with an increase in reported headaches, which may reflect the overlap with giant cell arteritis, or that some cases of GCA are not being recognised or misdiagnosed. Although females have a higher prevalence of headaches overall, males saw a much bigger increase in the prevalence of headaches compared with a similar age general population group. However, a Danish population survey suggested the prevalence of headache to be 36.5%, although only 17% had consulted primary care because of headache symptoms [15]. Previous studies comparing patients with isolated PMR and those who went onto develop GCA have suggested that new onset headache is a key predictor [16, 17], with others suggesting that the headache is over-relied on in making a GCA diagnosis [5, 6].
Given that single symptoms such as headache are common both in the general population and in those with PMR it may be that combinations of symptoms are more useful in identifying patients at risk of GCA. Headache and tender scalp are two of the most common symptoms reported in those diagnosed with GCA and were reported by around 10% of this PMR Cohort. Further follow-up will assess whether these patients were initially misdiagnosed as PMR instead of GCA, together with further assessment of the utility of combinations of symptoms in predicting those patients at higher risk of GCA.
