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Correspondence response

Decreases in diagnostic delay are supported by sensitivity analyses We thank Dr Sykes and colleagues1 for their interest in our publication2 on changes in diagnostic delay in patients with inflammatory arthritis from year 2000 to year 2011 and for their reflections regarding our investigations. Based on data from the nationwide Danish DANBIO registry, we studied diagnostic delay defined as the time between onset of symptoms and the time of diagnosis in 13 721 patients with rheumatoid arthritis (RA), psoriatic arthritis (PSA) and ankylosing spondylitis (AS). We found that for RA, PSA and AS, the delay decreased from 30 months, 53 months and 66 months, respectively in year 2000 to 3–4 months for all three diagnoses in year 2011. The prognosis for patients with RA is better with early diagnosis, which is reflected in national and international guidelines, and the principle of early referral has spread to PSA and AS. Little is, however, known about the extent to which these recommendations have transformed into earlier establishment of diagnosis in routine care. Data for our study were collected as part of clinical practice when patients were first registered in DANBIO. The large number of patients is an important strength. As mentioned in the discussion, however, potential sources of bias in study design should be considered, and among those are left and right censorship and channelling bias. Consistent with this, Sykes and colleagues suggest a potential methodological problem with a sample of patients defined by diagnosis, rather than by symptoms. Patients with few symptoms may not seek specialist medical care and have not been captured in DANBIO. This is perhaps most important for patients with AS symptoms, where the majority of patients has mild disease. This relevant worry was addressed in the paper. To estimate the impact of channelling bias and the robustness of our results, we performed a sensitivity analysis in which we only included patients treated with biological drugs. Coverage of this group of patients has consistently been more than 90% in DANBIO, thereby practically eliminating channelling bias. Reassuringly, the key findings of significant reduction in diagnostic delay were confirmed for all three diagnoses in this subgroup.2 Our findings of shorter diagnostic delay were also reported by other research groups. In one study of 135 patients with AS, the diagnostic delay was reported to decrease from 13 years in 1970 to 2 years in year 2000.3 Our

Ann Rheum Dis July 2014 Vol 73 No 7

paper showed that among patients who seek medical assistance (ie, not those individuals with mild symptoms that require no treatment) the diagnostic delay has dropped substantially during the first decade of the new millennium. The decrease probably reflects a stronger awareness of the importance of early diagnosis. J Sørensen,1 Merete Lund Hetland2,3 1

SDU, Odense, Denmark DANBIO, Center for Rheumatology and Spine Diseases, Glostrup, Denmark Institute of Health and Medical Sciences, Department of Medicine, University of Copenhagen, Denmark

2 3

Correspondence to Professor Merete Lund Hetland, Center for Rheumatology and Spine Diseases, DANBIO, Glostrup 2600, Denmark; [email protected] Competing interests None. Ethics approval Register study. Provenance and peer review Commissioned; internally peer reviewed.

To cite Sørensen J, Hetland ML. Ann Rheum Dis 2014;73:e45. Received 29 March 2014 Accepted 30 March 2014 Published Online First 16 April 2014

▸ http://dx.doi.org/10.1136/annrheumdis-2014-205589 Ann Rheum Dis 2014;73:e45. doi:10.1136/annrheumdis-2014-205590

REFERENCES 1

2

3

Sykes M, Doll H, Gaffney K. Comment on: ‘Diagnostic delay in patients with rheumatoid arthritis, psoriatic arthritis and ankylosing spondylitis: results from the Danish nationwide DANBIO registry’ by Sørensen et al. Ann Rheum Dis 2014; 73:e44. Sørensen J, Hetland ML. Diagnostic delay in patients with rheumatoid arthritis, psoriatic arthritis and ankylosing spondylitis: results from the Danish nationwide DANBIO registry. Ann Rheum Dis 2014. Published Online First: 17 Feb 2014. doi:10.1136/annrheumdis-2013-204867 Salvadorini G, Bandinelli F, Delle Sedie A, et al. Ankylosing spondylitis: how diagnostic and therapeutic delay have changed over the last six decades. Clin Exp Rheumatol 2012;30:561–5.

e45

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Decreases in diagnostic delay are supported by sensitivity analyses J Sørensen and Merete Lund Hetland Ann Rheum Dis 2014 73: e45 originally published online April 16, 2014

doi: 10.1136/annrheumdis-2014-205590

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Decreases in diagnostic delay are supported by sensitivity analyses.

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