Correlation between GAP index and DSP score in patients with pulmonary sarcoidosis

<bold>Introduction:</bold> Chronic respiratory diseases such as sarcoidosis are complex conditions that can lead to functional limitations with an unpredictable evolution. It is therefore useful to assess their prognosis using composite scores such as the Gender Age Physiology (GAP) index and the Distance Saturation Product (DSP). We aimed to study the correlation between GAP index and DSP score in patients with pulmonary sarcoidosis. <bold>Methods:</bold> This was a retrospective study involving 57 patients with sarcoidosis who were referred to our department. All patients underwent spirometry, measurement of Diffusing capacity of the Lungs for Carbon Monoxide (DLCO), and a 6-minute Walk Test (6MWT). The GAP score was calculated based on gender, age, and impact on respiratory function (Forced Vital Capacity [FVC] and DLCO), while the DSP score was calculated by multiplying the 6-minute Walk Distance (6MWD) by the minimum oxygen saturation recorded during the 6MWT (min SpO2). <bold>Results:</bold> The mean age was 55.23 ± 10.08 years with a female predominance (78.9%). The mean values for FVC (%) and DLCO (%) were 73.99 ± 21.22 and 62.86 ± 22.22, respectively. The mean values for min SpO2 (%) and 6MWD (meters) were 92.53 ± 6.35 and 454.86 ± 127.17, respectively. Moreover, the GAP score was negatively correlated with min SpO2 (r = -0.521; p < 0.001), 6MWD (r = -0.437; p < 0.001), and DSP score (r = -0.432; p < 0.001). <bold>Conclusion:</bold> Since that the DSP index is significantly correlated with the GAP index, pulmonologists should place greater importance on the 6MWT, which, in addition to its simplicity, helps them in better predicting the prognosis of this lung disease.