The utility of the modified desaturation distance ratio (mDDR) as a predictor of mortality in interstitial lung disease.

<bold>Introduction:</bold> In patients with interstitial lung disease (ILD), assessing exercise capacity, such as the six-minute walk test (6MWT), and evaluating oxygen saturation (SpO2) during exercise, play a fundamental role in assessing the severity, monitoring, and prognosis of ILD. <bold>Objective:</bold> To determine if the modified desaturation distance ratio (mDDR), a composite index integrating the six-minute walk distance (6MWD) and SpO2, is a better prognostic factor for mortality in patients with ILD. <bold>Methods:</bold> A retrospective study with an 8-year follow-up. We calculated the mDDR using 6MWD values and dividing them by the desaturation area, thus summing the difference between 100% SpO2 and the patient's SpO2 at initial and final test. Survival was analyzed using Kaplan-Meier analysis, and cut-off points were determined by obtaining the area under the curve from ROC analysis. <bold>Results:</bold> The study included 201 patients with ILD with a mean age of 65±12 years, with a similar percentage of men and women. For 6MWD, the ROC curve showed an AUC of 0.637 (95% CI: 0.557 to 0.716), p=0.001*. We calculated a cut-off of 491 meters with a sensitivity of 59% and a specificity of 36%. Regarding mDDR, the ROC curve showed an AUC of 0.700 (95% CI: 0.624 to 0.775), p<0.001*. We calculated a cut-off value of 31.84 for mDDR with a sensitivity of 59% and a specificity of 33%. In Figure 1, Kaplan-Meier curves and the survival of patients with 6MWD above and below 491 meters are observed; the log-rank (Mantel-Cox) test yielded a chi-square of 9.997, p=0.002*. On the other hand, for mDDR greater and less than 32, the log-rank (Mantel-Cox) test yielded a chi-square of 16.398, p=0.001*. <bold>Conclusions:</bold> mDDR has demonstrated a greater prognostic value than 6MWD in patients with ILD.