Statistical analysis

We described and compared the patient’s characteristics and clinical variables between PDH–proven patients, PDH–negative patients and the characteristics of the patients with HUAg false negative results. We used median and interquartile range (IQR) for continuous variables and frequencies and percentages for categorical variables and Mann-Whitney U and Pearson’s X² or Fisher´s exact test as statistical tests accordingly. A p-value ≤ 0.05 was determined as significant. We calculated sensitivity, specificity, positive predictive value, negative predictive value and positive likelihood ratio and their 95% confidence intervals (95% CI) of HUAg using as a standard of reference the cases classified as PDH–proven. We used the STATA 11.0 software (StataCorp LLC, College Station, TX) to perform the statistical analysis.