P149 Association between nailfold videocapillaroscopy findings and sKL-6 levels in patients with idiopathic inflammatory myopathies-related interstitial lung disease
Authors: Santos Cristiana Sieiro , Tandaipan Jose Luis , Castillo Diego , Martínez Martínez Laura , Codes Helena , Sainz Luis , Magallares Berta , Moya Patricia , Corominas Hector , Díez Álvarez Elvira , Castellvi Ivan 
Published: April 2024

Abstract

Background/Aims
Idiopathic inflammatory myopathies (IIM) are a heterogeneous group of acquired muscle diseases with distinct clinical, pathological and histological features. Interstitial lung disease (ILD) is a frequent pulmonary manifestation in IIM (IIM-ILD) and considerably influences morbidity and mortality. Krebs von den Lungen 6 (sKL-6) has been proposed as a potential biomarker reflecting the severity of ILD in connective tissue diseases. Raynaud’s phenomenon is very frequent and the presence of microvascular changes in IIM have been described however, the role of nailfold videocapillaroscopy (NVC) in diagnosis and prognosis in IIM is not clearly established. We aim to determine if there is any association between NVC findings, sKL-6 levels and pulmonary involvement in patients with inflammatory myopathies.

Methods
We performed a retrospective study of IIM patients followed in a reference center and compared them according to the presence of ILD. Epidemiological, clinical and immunological data, pulmonary function tests (forced vital capacity and diffusing capacity for carbon monoxide), sKL-6 levels and NVC finding were retrieved. Statistical analysis was performed by T-test and Fisher’s exact test to compare qualitative and/or quantitative variables and multiple logistic regression modelling to identify correlation between pulmonary function tests, NVC findings and sKL-6 levels.

Results
95 patients were included, 47 patients (49%) with ILD. 34% were male with a median age at inclusion of 55.3±24 years. Avascular areas and capillary lossshowed a significant association with the presence of ILD (OR 2.43, 95% CI 1.3-5.7, p 0.004) and (OR 1.7, 95% CI 1.48-3.1, p 0.04). A negative correlation between capillary loss and enlarged capillaries was also found with FVC% (β=-0.46, p 0.001 and β=-0.57, p &lt; 0.0001) and DLCO% (β=-0.32, p 0.04 and β=- 0.23, p 0.03), respectively. When we studied the correlation between sKL-6 levels, positive correlations with the presence of ILD (β = 0.77, p 0.0004), the presence of hemorrhages (β = 0.21, p 0.04) and avascular areas in NVC (β = 0.64, p 0.03) and negative correlations with FVC% (β=-0.47, p 0.001) and DLCO% (β=-0.59, p, 0.005) were found. Male sex, respiratory symptoms, %FVC and %DLCO, sKL-6 levels, anti-Jo1 positivity and the presence of avascular areas and enlarged capillaries in NVC were identified as IIM-ILD predictors (R2=0.974, p = 0.006).

Conclusion
Capillary loss and avascular areas showed a significant association with the presence of ILD, worse FVC and DLCO values and sKL-6 levels. We identified nine predictors for developing ILD in IIM. NVC assessment and sKL-6 levels can have a predictive role for studying pulmonary function and assessing the prognosis of IIM-ILD.

Disclosure
C. Sieiro Santos: None. J. Tandaipan: None. D. Castillo: None. L. Martínez Martínez: None. H. Codes: None. L. Sainz: None. B. Magallares: None. P. Moya: None. H. Corominas: None. E. Díez Álvarez: None. I. Castellvi: None.