Background/Purpose

Digital ulcers (DU) are painful and disabling and affect almost 50% of systemic sclerosis (SSc) patients. Nailfold videocapillaroscopy (NVC) non-invasively assesses SSc-related micro-angiopathy and may be useful in predicting clinical progression of digital vasculopathy, especially DU.^1-4The objective of this study was to identify NVC variables and clinical characteristics which predict the occurrence of new DU in SSc patients.

Methods

International, prospective, multicenter cohort study in SSc. Eligibility was not restricted by medication use. SSc patients (American College of Rheumatology/LeRoy and Medsger) were enrolled in two strata: ‘DU History’ and ‘No DU History’. The No DU History patients had early disease (≤2 years).

Variables were classified into bundles for statistical analysis: demographics, SSc clinical characteristics, DU characteristics, NVC characteristics and other clinical characteristics. NVC variables for fingers II–V were evaluated locally in a standardized way. Patients were followed up to 6 months for new DUs (confirmed by the investigator).  Univariable Logistic Regression (ULR) was performed on all variables and Multivariable Logistic Regression (MLR) was performed within and across bundles to assess statistical significance (Wald chi-square p<0.15 for linear and p<0.05 for quadratic) and discriminatory ability (receiver operation characteristic area under the curve [ROC AUC]). Clinical relevance to predict new DU in 6 months was portrayed by model performance characteristics in a binary risk chart and two-by-two tables at different risk probability thresholds.

Results

Of the 623 patients enrolled in 59 centers, 591 had data on DU outcome (new DU or no new DU) during the study. 468 (79%) patients had a DU history, of whom 103 (22%) developed new DU. 123 (21%) patients had no DU history, of whom 5 (4%) developed new DU. Due to low event numbers in the no DU history group, the present analysis focuses on the DU history stratum. The mean age was 54.0 years, 79.5% were females, and 59.8% patients had limited cutaneous SSc. The final model consisted of the following 3 co-variables to predict the occurrence of DU within 6 months: number of DU at baseline visit categorized into 0, 1, 2 and ≥ 3, mean number of capillaries in the middle finger of the dominant hand (evaluated on two adjacent fields in the middle of the nailfold) and presence/absence of critical digital ischemia at enrolment. AUC of this model was 0.738 (C.I. 0.681-0.795). Internal validation through bootstrap generated AUC 0.633 [C.I. 0.510-0.756]). At a probability threshold of 37.3%, the binary risk table shows a specificity of 90.6%, a sensitivity of 39.4%, a negative predictive value (NPV) of 83.8% and a positive predictive value (PPV) of 54.9%.

Conclusion

The CAP study is the first and largest prospective study producing a simple prognostic model with acceptable performance which can be useful in the management of patients with presence or history of DU.

References

1. Cutolo M et al. Nature Rev Rheumatol 2010;6:578–87; 2. Smith V et al. Ann Rheum Dis 2011;70:180–3; 3. Sebastiani M et al. Ann Rheum Dis 2012;71:67–70; 4. Smith V et al. Ann Rheum Dis 2012;71:1636-9

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/a-multicenter-prospective-cohort-study-using-nailfold-videocapillaroscopy-and-other-clinical-characteristics-to-determine-the-risk-of-developing-new-digital-ulcers-in-patients-with-systemic-sclerosis/