Correlation between DSP index and lung function in patients with pulmonary sarcoidosis

<bold>Introduction:</bold> The Distance Saturation Product (DSP) is a composite index obtained during the 6-Minute Walk Test (6MWT) and has prognostic value in several respiratory pathologies. <bold>Objective:</bold> The aim of our study was to evaluate the association of the DSP index with spirometric parameters and Carbon Monoxide Diffusing Capacity (DLCO) in patients with pulmonary sarcoidosis. <bold>Methods:</bold> This was a retrospective study of 70 patients with pulmonary sarcoidosis referred to the Pulmonary Function Test Department at Abderrahmane MAMI Hospital (July-December 2023). Spirometry, DLCO and 6MWT were performed for all patients. The DSP index was calculated by multiplying the 6-Minute Walk Distance in meters (6MWD) and the lowest oxygen saturation during 6MWT (SpO2). <bold>Results:</bold> Mean age was 55.17±10.29 years with a female predominance (77.1%). The spirometric profiles were distributed as follows : 58.8% had normal spirometry, 33.8% had a restrictive ventilatory disorder and 7.4% had an obstructive ventilatory disorder. Means of FEV1 (%), FVC (%) and DLCO (%) were 76.16±19.45, 76.38±20.30 and 64.44±22.47, respectively. Mean of 6MWD in meters was 453.74±122.01 and mean of the lowest SpO2 (%) was 92.41±6.40. The mean of DSP was 419.82±127.19. Statistical analysis revealed that the DSP score was significantly correlated with FVC (%) (r = 0.309; p = 0.044) and DLCO (r =0.428 ; p=0.006). However, no significant correlation was found between DSP and FEV1. <bold>Conclusion:</bold> DSP could be a useful tool for functional assessment in patients with sarcoidosis