Letters to the Editor

calculated by averaging the remaining items in case of a maximum of one or three MIs, respectively. Rheumatology key message .

Up to one missing item for BASDAI and three for BASFI can reliably be imputed when assessing patients with AS.

Acknowledgements S.R. was supported by Fundac¸a˜o para a Cieˆncia e Tecnologia (FCT) grant SFRH/BD/68684/2010.

Sofia Ramiro1,2, Astrid van Tubergen3,4, De´sire´e van der Heijde5, Filip van den Bosch6, Maxime Dougados7 and Robert Landewe´1,8

6 van der Heijde DM, van’t Hof M, van Riel PL et al. Development of a disease activity score based on judgment in clinical practice by rheumatologists. J Rheumatol 1993;20:579–81. 7 van Gestel AM, Prevoo ML, van’t Hof MA et al. Development and validation of the European League Against Rheumatism response criteria for rheumatoid arthritis. Comparison with the preliminary American College of Rheumatology and the World Health Organization/International League Against Rheumatism Criteria. Arthritis Rheum 1996;39:34–40. 8 Zochling J, van der Heijde D, Burgos-Vargas R et al. ASAS/EULAR recommendations for the management of ankylosing spondylitis. Ann Rheum Dis 2006;65:442–52. 9 Rubin DB. Multiple imputation for nonresponse in surveys. New York: Wiley.

1

Department of Clinical Immunology and Rheumatology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands, 2Department of Rheumatology, Hospital Garcia de Orta, Almada, Portugal, 3Department of Medicine, Division of Rheumatology, Maastricht University Medical Center, 4School for Public Health and Primary Care (CAPHRI), University of Maastricht, Maastricht, 5Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands, 6 Department of Rheumatology, Ghent University Hospital, Ghent, Belgium, 7Rheumatology B Department, Cochin Hospital, Paris-Descartes University, Paris, France and 8Department of Rheumatology, Atrium Medical Center, Heerlen, The Netherlands. Accepted 18 October 2013. Correspondence to: Sofia Ramiro, Department of Clinical Immunology and Rheumatology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. E-mail: [email protected]

References 1 Calin A, Garrett S, Whitelock H et al. A new approach to defining functional ability in ankylosing spondylitis: the development of the bath ankylosing spondylitis functional index. J Rheumatol 1994; 21:2281–5. 2 Garrett S, Jenkinson T, Kennedy LG et al. A new approach to defining disease status in ankylosing spondylitis: the bath ankylosing spondylitis disease activity index. J Rheumatol 1994;21: 2286–91. 3 Spoorenberg A, van der Heijde D, de Klerk E et al. Relative value of erythrocyte sedimentation rate and C-reactive protein in assessment of disease activity in ankylosing spondylitis. J Rheumatol 1999;26:980–4. 4 Auleley GR, Benbouazza K, Spoorenberg A et al. Evaluation of the smallest detectable difference in outcome or process variables in ankylosing spondylitis. Arthritis Rheum 2002;47:582–7.

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Rheumatology 2014;53:376–377 doi:10.1093/rheumatology/ket386 Advance Access publication 4 December 2013

Further confirmation that digital ulcers are associated with the severity of abnormality on nailfold capillaroscopy in patients with systemic sclerosis SIR, In a recent pilot study in a cohort of patients with SSc, Smith et al. [1] demonstrated an association between nailfold videocapillaroscopy (NVC) patterns and the severity of peripheral vascular involvement, as assessed after 18–24 months. These findings lend further support to the proposal that the severity of abnormality on NVC may serve as a useful biomarker for the prediction of digital ulceration in SSc [2, 3]. As part of a prospective, singlecentre study examining the prevalence of SSc-related digital ulcers (DUs) [4], we used quantitative NVC to assess whether microvascular abnormalities were associated with the presence of current DUs. The North West Greater Manchester National Research Ethics Service Committee approved the study. As previously reported [4], patients attending specialist SSc clinics between January and December 2009 were invited to participate and, following informed consent, each was assessed by a specialist nurse who documented the presence or absence of active DUs. An active DU was defined as a distinct lesion with loss of epidermis. Data on point prevalence and physical function are reported elsewhere [4]. Following acclimatization in a temperature-controlled laboratory, patients underwent quantitative NVC of the non-dominant ring finger as previously described [5]. In brief, panoramic, high-magnification (300) images of the distal nailfold capillary row were acquired. A vascular technician manually marked up the

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Disclosure statement: The authors have declared no conflicts of interest.

5 Bruynesteyn K, Boers M, Kostense P et al. Deciding on progression of joint damage in paired films of individual patients: smallest detectable difference or change. Ann Rheum Dis 2005;64:179–82.

Letters to the Editor

TABLE 1 Nailfold capillaroscopic parameters in 121 patients with SSc Capillaroscopy, semi-automated measurements

No digital ulcers, median (range) (n = 111)

Digital ulcers, median (range) (n = 10)

Mean difference (95% CI)

P-value

Intercapillary distance (arbitrary units)a Capillary width (arbitrary units) Derangement (arbitrary units) Tortuosity (arbitrary units), manual Measurement, number/mm

26 914 (19 998–45 927) 15.0 (12.0–17.4) 11.9 (8.8–14.9) 3.31 (3.23–3.37) 4.9 (3.5–7.2)

49 923 (38 755–63 221) 14.3 (12.6–16.3) 13.5 (8.6–14.3) 3.31 (3.20–3.42) 3.3 (3.0–4.4)

1.60 (1.04, 2.46) 0.1 (2.5, 2.4) 0.1 (3.2, 3.3) 0.03 (0.11, 0.06) 1.4 (3.0, 0.2)

0.03 0.96 0.97 0.54 0.09

a

Analysed on a log scale, so difference and CI are a multiplying factor between geometric mean values of the two groups.

Rheumatology key message .

SSc-related digital ulcers are associated with increased intercapillary distance.

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Funding: We are grateful to the Raynaud’s and Scleroderma Association for funding this study. Disclosure statement: The authors have declared no conflicts of interest.

Holly Ennis1, Tonia Moore1, Andrea Murray1, Andy Vail2 and Ariane L. Herrick1 1

Centre for Musculoskeletal Research, Salford Royal NHS Foundation Trust and 2Centre for Biostatistics, Institute of Population Health, Manchester Academic Health Science Centre, Manchester, UK. Accepted 1 October 2013 Correspondence to: Ariane Herrick, Clinical Sciences Building, Salford Royal NHS Foundation Trust, Salford M6 8HD, UK. E-mail: [email protected]

References 1 Smith V, Decuman S, Sulli A et al. Do worsening scleroderma capillaroscopic patterns predict future severe organ involvement? A pilot study. Ann Rheum Dis 2012; 71:1636–9. 2 Sebastiani M, Manfredi A, Colaci M et al. Capillaroscopic skin ulcer risk index: a new prognostic tool for digital skin ulcer development in systemic sclerosis patients. Arthritis Rheum 2009;61:688–944. 3 Smith V, De Keyser F, Pizzorni C et al. Nailfold capillaroscopy for day-to-day clinical use: construction of a simple scoring modality as a clinical prognostic index for digital trophic lesions. Ann Rheum Dis 2011;70: 180–3. 4 Ennis H, Vail A, Wragg E et al. A prospective study of systemic sclerosis-related digital ulcers: prevalence, location and functional impact. Scand J Rheum 2013, DOI:10.3109/ 03009742.2013.780095. 5 Murray A, Feng K, Moore T et al. Preliminary clinical evaluation of semi-automated nailfold capillaroscopy in the assessment of patients with Raynaud’s phenomenon. Microcirculation 2011;18:440–7.

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capillary apices. Customized software was then used to calculate automated measures of intercapillary distance, capillary width, tortuosity (defined as the amount of change in the direction of an individual capillary’s direction, or how ‘curly’ it is) and derangement (defined as the variance in the direction of all the capillaries marked up). All measurements were made in arbitrary units. In addition to these semi-automated measurements, the initial apex mark-up was used as a direct measure of capillaries per millimetre. Unifactorial logistic regression was applied to assess association with ulcer status of capillaroscopy scores. Analyses were performed using Stata statistical software (version 10; StataCorp, College Station, TX, USA). NVC data were available for 121 of the 148 patients who participated in the study [10 with ulcers and 111 without, 104 (86%) female, median age 60 years (range 21–88), median RP duration 18 years (range 4–69), median disease duration 12 years (range 3–54)] and are shown in Table 1. NVC data for the remaining 27 patients were unavailable for one of the following reasons: results being uninterpretable (i.e. capillaries not clearly visualized), or the patient did not undergo capillaroscopy due to the presence of contracture or due to time constraints in the clinic. For the semi-automated measurements, intercapillary distance was greater in patients with active ulcers [log (intercapillary distance), P = 0.03]. Consistent with this, capillary density was lower, although not significantly (P = 0.09), in patients with DUs. Capillary width, tortuosity and derangement were not significantly different in patients with or without ulcers (P = 0.96, P = 0.97 and P = 0.54, respectively). The finding that intercapillary distance was greater in those with current DUs is further evidence that patients with the most marked microvascular abnormalities (as assessed by NVC) are most likely to develop DUs, and lends further support for NVC as a clinical biomarker in patients with SSc.