Department of Rheumatology, Nuffield Orthopaedic Centre, Oxford OX3 7LD, UK
Correspondence to: L. Williamson, The Great Western Hospital, Swindon SN1 4JU, UK. E-mail: lyn.williamson{at}smnhst.swest.nhs.uk
SIR, We read with great interest the comprehensive review of treatment for psoriatic arthritis (PsA) by Pipitone and colleagues [1]. We have recently undertaken a study of patients with PsA and wish to discuss several points raised in this review.
We studied 103 patients with PsA (48 women, 55 men, mean age 45 ± 12 years) from January 1999 to August 2000. These patients were recruited from out-patient clinics in Oxford, UK. Eighty-three (80.6%) patients were taking non-steroidal anti-inflammatory drugs (NSAIDs) and 40 (38.8%) were prescribed disease-modifying anti-rheumatic drugs (DMARDs), most commonly methotrexate and sulphasalazine. A careful history was taken about the patterns of arthritis. The skin and musculoskeletal systems were examined by assessors blinded to the results of HLA-B27 testing. HLA-B27 was tested in 98 patients. Of the 103 patients invited, 68 underwent magnetic resonance imaging (MRI) of the sacroiliac joints. MRI findings of sacroiliitis were found in 26/68 (38%) patients [2].
The first issue we wish to address is the role of HLA-B27 in psoriatic arthritis. The authors of [1] state that HLA-B27 is strongly associated with axial disease in PsA. In our study, HLA-B27 was detected in 20/98 (20%) patients. This compares with the frequency in the general UK population of 9.5% (P<0.0001). Although the presence of HLA-B27 was strongly associated with iritis and palmoplantar pustulosis [3], there was no association between HLA-B27 and the presence of clinically or MRI-diagnosed sacroiliitis, limited spinal movements, the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) or the Bath Ankylosing Spondylitis Functional Index (BASFI). Overall, the positive predictive value of HLA-B27 for sacroiliitis on MRI was only 45.5% and the negative predictive value was 63.6% [2]. Therefore, our data suggest that in UK hospital out-patients with PsA, HLA-B27 testing is of little clinical value in predicting the presence of axial disease.
We concur with the authors observation that PsA runs a variable course. Furthermore, we wish to emphasize that both inter- and intra-patient variation may occur in PsA. In the 101 patients with a disease duration of >6 months, there were 54 (53.5%) patients with a remitting and relapsing disease course and 47 (46.5%) patients with unremitting and progressive disease. Those patients with unremitting and progressive disease were more likely to have polyarticular type disease (P<0.05), but also impaired function as measured by Health Assessment Questionnaire (HAQ), even after adjusting for polyarticular disease (P<0.01). We believe that these results are relevant to the treatment of PsA for several reasons. First, over half of our patients have a fluctuating disease course irrespective of drug treatments. Such fluctuations may contribute to the high placebo response that is well documented in clinical trials in PsA [4]. In addition, maldistribution of disease course between placebo and treatment arms may also affect the results of clinical trials.
The authors emphasize the increasing availability of registered drugs for PsA. In addition, the use of over the counter (OTC) medications is also rising. We studied the intake of complementary therapies in this group of patients with PsA using self-reported questionnaires. Eighty-four (82%) patients returned questionnaires. Of these, 34 (40%) used OTC medications in addition to their prescribed drugs. The most commonly used preparations were cod liver oil (19 patients), oil of evening primrose (11 patients) and vitamin E (6 patients). Other preparations reported included glucosamine/chondroitin, garlic, green-lipped mussel extract, starflower oil, sulphur, devil's claw, Chinese herbs and vitamin and mineral supplements. Twenty-two (26%) patients sought the help of alternative or complementary practitioners. Some of these OTC medications, especially the herbal preparations, are pharmacologically active and may be hepatotoxic or interact with prescribed medication [5]. We believe that these data emphasize the importance of taking a full history of both prescribed and OTC medication in all patients, particularly those with rheumatic diseases where response to conventional therapy can be variable. Rheumatologists should also make themselves aware of possible interactions between conventional and OTC therapies.
Patients gave consent and ethical approval was obtained from the Central Oxford Research Ethics Committee. This study was funded by an Oxford District Research Grant. N. Dalbeth is the Rose Hellaby Rheumatology Fellow 2002.
The authors have declared no conflicts of interest.
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