Comparison of the Rating Scale and the Standard Gamble in Measuring Patient Preferences for Outcomes of Gallstone Disease

To estimate patient preferences for gallstone-related treatments and outcomes, and assess how preferences vary by patient characteristics and scaling technique, the authors randomly assigned 40 patients without gallstones to interviews based on a rating scale (n = 22) and a standard gamble (n = 18). The patients assigned preference values (possible values 0 to 1) to open cholecystectomy (mean 0.45 by rating scale, 0.78 by standard gamble), laparoscopic cholecystectomy (0.71, 0.91), extracorporeal shock-wave lithotripsy (0.77, 0.89), acute cholecystitis (0.36, 0.77), lifetime biliary colic (0.41, 0.71), postcholecystectomy syn drome (0.43, 0.79), asymptomatic stone necessitating treatment with bile acids (0.76, 0.96), and surgical scar (0.79, 0.998). Preferences varied little by age, gender, or race. Standard gamble values were highly correlated with, but significantly greater than, rating scale values. The authors conclude that patients' preferences for gallstone-related conditions generally are significantly less than one, and differ markedly by the scaling technique used to derive them. These results should be considered when patient preferences are incorporated into analyses of gallstone treatments. Key words: patient preference values; rating scale; stan dard gamble; gallstones; cholecystectomy; lithotripsy. (Med Decis Making 1994;14:307- 314)