Background: Diabetic neuropathy is the most common complication of diabetes, the effective control of which requires accurate diagnosis of neuropathy on a regular basis. The present study aimed to investigate the factors affecting the event time of neuropathy using the Clayton copula model in type 2 diabetic patients in the presence of a surrogate response variable.
Methods: The data of all the people whose diabetes test results were negative in the 2006 screening by the health centers in Fereydun Shahr, Isfahan, but their diabetes re-tests were positive in 2007, and were at least 30 years of age were collected, and their neuropathy status was followed up for at least 10 years. To investigate the factors affecting the event time of neuropathy in the patients, the Clayton copula model as well as the true variable, ten-point monofilament test and surrogate variable, and Michigan questionnaire including interviews and examinations by a trained physician were used. All the statistical analyzes were performed using the R software (version 3.6.2) and tests were done with an error of 0.05.
Results: Of the total of 371 diabetic patients studied, 114 (30.7%) were male and their mean age was 63.93 (±0.568) years. According to the Clayton copula model, the individuals with a family history of diabetes and Hemoglobin A1c of >=8.1, BMI of >=35, HDL of <54, and under treatment with oral and insulin injections would develop neuropathy more quickly.
Conclusion: In this study, using the survival ROC curve, was shown that the Copula model was more efficient than the surrogate model, so it is suggested that the Copula model be used to predict the occurrence of neuropathy for patients who do not have access to the monofilament test. Keywords: Type 2 Diabetes, Neuropathy, Michigan Questionnaire, Monofilament Test