Diabetes in urban African-Americans. XIX. Prediction of the need for pharmacological therapy

OBJECTIVE - To develop a prediction rule that will identify patients who will require pharmacological therapy within 6 months of first presentation to a diabetes clinic. RESEARCH DESIGN AND METHODS - Among the patients who came to the Grady Diabetes Clinic between 1991 and 1997, we randomized 557 frequent attenders to a development group and 520 frequent attenders to a validation group. Using multiple logistical regression, we derived a prediction rule in the development group to project whether patients would require pharmacological intervention to achieve HbA(1c) levels <7% after 6 months. The utility of the prediction rule was then confirmed in the validation group and tested prospectively on an additional group of 93 patients who presented from 1997 to 1998. Performance of the prediction rule was assessed using receiver operating characteristic (ROC) curves. RESULTS - The rule (-4.469 + 1.932 X sulfonylurea Rx + 1.334 X insulin Rx + 0.196 x duration + 0.468 x fasting glucose, where 'Rx' indicates a prescription) predicted the need for pharmacological intervention in the development group (P < 0.0001). Use of insulin or sulfonylurea therapy at presentation, duration of diabetes, and fasting glucose levels were significant predictors of the future need for pharmacological management. The prediction rule also performed well in the validation group (positive predictive value 90%, correlation between predicted and observed need for medical management 0.99). ROC curves confirmed the value of the prediction rule (area under the curves was 0.91 for the development group, 0.85 for the validation group, and 0.81 for the prospective group). CONCLUSIONS - Early identification of individuals who will require pharmacological intervention to achieve national standards for glycemic control can be achieved with high probability, thus allowing for more efficient management of diabetes.