The cumulative number of micro-haemorrhages and micro-thromboses in nailfold videocapillaroscopy is a good indicator of disease activity in systemic sclerosis: a validation study of the NEMO score

Abstract

Background: Some abnormalities in nailfold videocapillaroscopy (NVC), such as the presence of micro-haemorrhages (MHEs), micro-thromboses (MTs), giant capillaries (GCs) and reduction in the number of capillaries (nCs), suggest a disease activity (DA) phase in systemic sclerosis (SSc). In a previous paper, we showed that the number of micro-haemorrhages and micro-thromboses (the so-called NEMO score) was the NVC feature more closely associated with DA. The present study was aimed at validating the NEMO score as a measure of DA in patients with SSc.

Methods: Two cohorts of 122 and 97 patients with SSc who were referred to two different rheumatology units, one in Milan and one in Naples, respectively, constituted the validation cohorts. The NEMO score, the total number of GCs and the mean nCs per digit were the parameters defined in each patient by eight-finger NVC. An expert operator analysed the NVCs in each of the participating units. The European Scleroderma Study Group (ESSG) index was used to define the DA level in each patient at the time of NVC examination.

Results: The NEMO score was the NVC parameter more strictly correlated with the ESSG score in both the Milan and Naples cohorts (p < 0.0001), and it was the only one among the NVC variables that gave a significant contribution in a logistic model where the ESSG score represented the dependent variable. ROC curve analysis confirmed that the NEMO score had the best performance in measuring DA. The AUC of the NEMO score was significantly greater than the AUCs obtained by plotting the sensitivity and specificity of the number of GCs and the mean nCs (p < 0.0001 in all cases). The NEMO score values that showed the best sensitivity-specificity balance in capturing patients with a relevant DA level were slightly higher in the Naples cohort than in the Milan cohort.

Conclusions: This study confirms that the presence of a certain number of MHEs and MTs in NVC may be considered a strong warning signal of a current phase of DA in patients with SSc.

Keywords: Disease activity; Nailfold videocapillaroscopy; Systemic sclerosis.

Fig. 1

Different nailfold videocapillaroscopic (NVC) features observed in our patients with systemic sclerosis. a and b A series of dilated capillaries. a None of the observed capillaries reaches the limit of 50 μm and so were not defined as giant capillaries (GCs), the larger one having a diameter of 35 μm. b One of these capillaries has a diameter of 83 μm, so it can be classified as a GC. c An NVC picture where one deposit of hemosiderin (1) indicating a previous micro-haemorrhage is present distal to the capillaries aligned in the cuticle. Multiple micro-thromboses are evident in the largely dilated capillaries, and a hemosiderin deposit can be observed distally in the right side of (d), just distal to capillary 6. In (c) and (d), the number of micro-haemorrhages and micro-thromboses scores were 2 and 49, and the European Scleroderma Study Group index scores were 1 and 7, respectively

Fig. 2

ROC curves built by plotting the sensitivity and specificity values of the number of micro-haemorrhages and micro-thromboses (NEMO) score (squares), giant capillary (GC) count (circles), and mean number of capillaries (nCs; triangles) in correctly classifying patients with either European Scleroderma Study Group (ESSG) index scores ≥3 or ≥3.5 are shown for both the Milan (left) and Naples (right) cohorts. In both cohorts, the AUC of the NEMO score was always significantly greater than the AUCs designed by plotting both the GC counts and the mean nCs (p < 0.0001). Conversely, no differences were found when we compared the AUC of the GC and capillary counts of both cohorts