Is speed of healing a good predictor of eventual healing of pyoderma gangrenosum?

Background Pyoderma gangrenosum is a rare inflammatory skin condition. Two prospective studies have evaluated treatments for pyoderma gangrenosum using a primary outcome of healing speed at 6 weeks. Objective Using data from both studies we assessed the predictive value of 3 early predictors for healing at 6 months: speed of healing, Investigator Global Assessment (IGA), and resolution of inflammation, recorded at 2 and 6 weeks. Methods Logistic regression models were applied and the effectiveness of the 3 measures was assessed through estimating the positive and negative predictive values and the area under the receiver operating characteristic curve. Results The positive and negative predictive value at 6 weeks were, respectively, 63.5% (95% confidence interval [CI] 52.4%-73.7%) and 74.6% (95% CI 62.5%-84.5%) for speed of healing; 80% (95% CI 68.7%-88.6%) and 74.2% (95% CI 64.1%-82.7%) for IGA; and 72.1% (95% CI 59.9%-82.3%) and 68.1% (95% CI 57.7%-77.3%) for resolution of inflammation. IGA had the best combined positive predictive value, negative predictive value, and area under the receiver operating characteristic curve at 2 and 6 weeks. Limitations We were limited by data available from existing datasets. Conclusion Speed of healing, IGA, and resolution of inflammation were all shown to be good predictors of eventual healing of pyoderma gangrenosum.