[Construction of an ultrasound clinical scale for the diagnosis of choledocolithiasis]. / Construcción de una escala clínica-ultrasonográfica para el diagnóstico de coledocolitiasis.

OBJECTIVE: to describe the construction of a clinical ultrasonographic scale for diagnosing choledocholithiasis. MATERIAL AND METHODS: A retrospective study of diagnostic tests, done through files of patients older than 18 years old with diagnosis related to having jaundice, who received care at three hospital facilities in Culiacan, Sinaloa, Mexico from 1998 to 1999, was carried out. Clinical, lab and cabinet data were collected. Gold standards were considered endoscopic retrograde cholangio-pancreatography as well as exploratory laparotomy. A diagnostic scale for choledocholithiasis was constructed through logistic regression and multivariate analysis using principal components. Sensitivity, specificity, prediction values, negative and positive likelihood ratio (LR) and ROC curves were estimated. The threshold model was applied for medical decision making. RESULTS: For detecting choledocholithiasis the scale's sensitivity was 98%, specificity was 95%, positive and negative predictive values were 95% and 97%, respectively. The estimated positive LR was 19.6 and negative 0.02. CONCLUSIONS: In adult patients up to 70 years with acute jaundice evolution, the scale can diagnose securely choledocholithiasis. The pretest prevalence and/ or probability do not affect importantly its accuracy for medical decision making.