A Medical Record-based Pilot Study on the Diffusing Capacity of the Lungs for Carbon Monoxide versus Nailfold Capillaroscopy as an Early Marker for Lung Involvement in Connective Tissue Disease-related Interstitial Lung Diseases

Abstract

Abstract Background: Connective tissue disease (CTD)-related interstitial lung diseases (ILDs) are one of the most common ILDs which affect relatively younger populations and can lead to extensive lung damage and fibrosis. Early detection and initiation of anti-inflammatory therapy can curtail the extent of lung damage. The diffusing capacity of the lungs for carbon monoxide (DLCO) is a well-established early marker of ILD. While most of the studies have shown specific nailfold capillaroscopy (NFC) findings in patients with CTD-ILD, none of them has evaluated the relation between diffusion impairment and nailfold capillary changes. The present study was carried out to evaluate the relationship between DLCO and NFC as markers for lung involvement in CTD-ILDs. Materials and Methods: This was a medical record-based observational study wherein the medical records of 100 diagnosed patients of CTD-ILD attending the pulmonology and rheumatology outpatient department were screened. Data concerning NFC, spirometry, and DLCO were collected and analyzed. Results: In our study of 100 patients, the minimum age was 29 years, and the maximum age was 78 years. A majority of patients in the study were found to be males (58%) and were suffering from CTD-ILD for a duration ranging from 2 to 5 years (58%). Eighty-nine percentage had a functional impairment on spirometry in the form of reduced forced vital capacity, and 61% had impaired DLCO. Nailfold capillary abnormalities were observed in all but one patient. The most common abnormal finding was a loss of capillary density (95% of patients) and a decrease in the intercapillary distance (94% of patients). A significant correlation was seen between diffusion impairment and abnormal nailfold capillary length. However, there was no significant correlation between DLCO and overall nailfold capillary abnormalities. Conclusion: The study concludes that NFC cannot be used as a tool to monitor diffusion impairment of the lungs in CTD-ILD. DLCO is a better assessment method compared to NFC changes as an indicator of lung involvement in CTD-ILD.