RESUMO
The optimal cut-off value of 24-hour (h) urinary copper (Cu) levels to identify Wilson's disease (WD) has not been widely studied in children. In sixty-six children with confirmed WD and 88 children without WD, 24-h urinary excretion of Cu at the time of diagnosis was studied. The receiver operating characteristic (ROC) curves revealed that the optimal cut-off value of urinary Cu to identify WD was 70 mcg [area under the curve (AUC) = 0.894] with a sensitivity and specificity of 81.8% and 89.8%, respectively. When the serum ceruloplasmin level was < 20 mg/dl and the 24-h urinary excretion of Cu was >70 mcg, the sensitivity was 75.8%, and the specificity was 97.7%. After the exclusion of cholestatic patients, the ROC curves revealed that the optimal cut-off value for 24-h urinary Cu excretion was 55 mcg (AUC = 0.910) with a sensitivity and specificity of 83.3% and 90.3%, respectively. When the ceruloplasmin level was <20 mg/dl and the 24-h urinary Cu excretion was >55 mcg, the sensitivity and specificity were 77.3% and 98.4%, respectively. A 24-h urinary Cu level of >70 mcg plus a ceruloplasmin level of < 20 mg/dl in the patients, and a 24-h urinary Cu level of >55 mcg plus a ceruloplasmin level of <20 mg/dl in non-cholestatic patients exhibited the highest specificity and the highest positive and negative predictive values to identify WD in children.
