Based on the predicted probability of 1-year survival, patients were stratified into 5 risk groups.
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The study found an overall survival rate of 87.4% (95% confidence interval [CI], 82.9–90.7%), representing 36 deaths (14 patients were lost to follow-up before one year).
When looking at outcomes based on risk group, patients identified by either the prognostic equation or risk score as being at high risk appeared to experience the worst survival rates. The study found that although in general the REVEAL equation adequately predicts outcomes in a newly diagnosed SSc-PAH population, the model performed less well in patients at highest risk of death.
To validate the model’s predicative accuracy, the investigators assessed model fit, discrimination and calibration. Using concordance statistics (c-indexes) for both the prognostic equation and the risk score, the investigators found both demonstrated good discrimination (0.734, 95% CI, 0.652–0.816 and 0.743, 95% CI, 0.663–0.823, respectively) comparable to the model. The overall model slope indicated only a marginal fit to the model (slope of 0.707, 95% CI, 0.400–1.014; P=0.06). Less valid was the magnitude of risk assigned to a low distance on a six-minute walk test and elevated brain natriuretic peptide (BNP), and model calibration was particularly poor for the highest risk groups.
“Discrimination and calibration appear to be less accurate in patients in the highest risk groups, indicating the REVEAL prediction model may not perform adequately in separating and predicting survival in the newly diagnosed SSc-PAH patients with the high-risk features and the lowest predicted probabilities of one-year survival,” state the authors.1
Dr. Mathai says he and his colleagues think the variation from predicted survival in the high-risk patients based on the REVEAL score is likely due to the greater emphasis placed on two measures in the study, the six-minute walk distance and blood levels of N-terminal pro brain natriuretic peptide. “Previous research by our group has demonstrated that both of these measurements have different prognostic relevance in SSc-PAH patients compared to PAH patients with other forms of the disease,” he says.
Based on these findings, Dr. Mathai underscored the usefulness of the REVEAL equation to predict outcomes in SSc patients with newly diagnosed PAH, but cautioned it may not accurately reflect the risk in patients at the highest risk of worse outcomes.
“It is important for providers and SSc-PAH patients to discuss prognosis on an individual basis to inform treatment plans and goals of care,” he says.
Mary Beth Nierengarten is a freelance medical journalist based in Minneapolis.