 |
|
|
 |
Dr. Mahr, et al reply To the Editor: Lane, et al raise a number of methodological concerns inherent to the study of seasonality in the onset of Wegener's granulomatosis (WG); most of these issues were also discussed in our article. Although complex to study, this question merits examination for several reasons, including the need to address the hypothesis that WG preferentially starts during the winter. Notably, one of the first surveys to provide "evidence for a seasonal variation in the onset of symptoms (highest in winter)" was based on the same background population, and an extensively overlapping observation period (1988–94)1, as those for the data given in Lane's letter that no longer support the initial finding. Our study was designed to bypass as much as possible the methodological pitfalls to which Lane, et al refer. As opposed to their now reported investigation, our study was entirely devoted to the assessment of the season of disease onset. Patient interviews took place at most 4 years after diagnosis of WG to attempt to accurately discern its season of onset. We acknowledge that, similar to Lane's study, our results may have suffered from statistical fluctuation due to the small sample size. Conversely, we respectfully disagree with the implication that investigating seasonality of WG onset requires a population-based study design. That reasoning would imply that patients seen at a referral center or participating in a clinical trial are non-random with respect to the season of disease onset, an assumption that appears unlikely, both in general and in the setting of our specific study. The conflicting findings of our, Lane's, and another recently published study2 add to the uncertainty about whether the onset of WG is influenced by a particular seasonal pattern. However, we may have to wait for more data on WG epidemiology to decide if these divergent conclusions are solely attributable to methodological flaws. ALFRED MAHR, MD, MPH, Vasculitis Center, Boston University School of Medicine, Boston, Massachusetts, USA; JOËL COSTE, MD, PhD, Department of Biostatistics; LOÏC GUILLEVIN, MD, Department of Internal Medicine, Hôpital Cochin, Paris, France. Address reprint requests to Dr. A. Mahr, Boston University School of Medicine, Vasculitis Center, E5, 715 Albany Street, Boston, MA 02118. E-mail: amahr@bu.edu 2. Pavone L, Grasselli C, Chierici E, et al. Outcome and prognostic factors during the course of primary small-vessel vasculitides. J Rheumatol 2006;33:1299-306. |