Decreasing the Risk of Diabetic Retinopathy in a Type 2 Diabetes Study: Part 1

Between 1 July 1995 and 30 June 1999, a randomized, controlled study of subjects aged ?18 years who had type 2 diabetes of at least 1-year duration was conducted in southern California. Detailed information about the methods used in this study was presented in an earlier publication and will be briefly summarized here. Subjects with type 2 diabetes, as defined by the American Diabetes Association, were recruited at clinical sites in Santa Barbara, Los Angeles, and San Diego counties, three California counties serving predominantly ethnic minority, low-income Medicaid (called Medi-Cal in California) populations. Although specific income data were not collected as part of this study, overall 93.9% of the Medi-Cal–eligible population is classified as medically indigent or needy or is eligible for public assistance. Two of these sites, in Santa Barbara and Los Angeles counties, had access to fundus cameras and participated in the retinal photograph component of the study, and the data provided in this manuscript are limited to those two sites. Signed, witnessed, informed consent was obtained from all prospective participants using forms approved by local institutional review boards.

As previously described, the main trial recruited participants with HbA1c (A1C) levels >7.5%. At the two participating sites, 121 subjects were randomized to the intervention group and 119 to the control group. Intensive diabetes case management was provided to the intervention group in addition to the standard care that was received by both groups from a primary physician not connected with the trial. In the intervention group, subjects were seen or contacted by the case management staff at varying intervals according to the need (at least monthly) to lower A1C. In the control group, blood for A1C determination was collected at 6-month intervals, and contact between study staff and participants was generally limited to that needed to assure collection of A1C samples or to obtain retinal photographs. All subjects, in both the intervention and control groups, were referred for retinal photographs at baseline and then at least yearly. Two hundred subjects (98 control and 102 intervention subjects) had at least one photograph and 149 (70 control and 79 intervention subjects) had least two sets of retinal photographs that could be analyzed in this study. For subjects with more than two sets of photographs, only the first and last were used in this analysis. Only the main study had sufficient power to see differences in metabolic variables. Thus, for this small ancillary study of retinopathy, which utilized only two of three original participating centers, follow-up analyses of A1C, blood pressure, and lipids were not planned. Photographs were obtained at a separate case management visit, and, after baseline, photographs were not necessarily scheduled to coincide with the laboratory tests or physical examinations.

The study staff at each site, consisting of registered nurses and registered dietitians working in close collaboration with an endocrinologist, provided diabetes case management to the intervention group only. Evidence-based practice guidelines and algorithms for oral medicines and insulin initiation and adjustment were used in a collaborative practice model with the primary care provider. Treatment goals and targets for therapy were uniform across sites, with flexibility to utilize individualized treatment algorithms and strategies at each site. Interactions between the participant and study staff occurred in person at the clinic site and via telephone between visits as needed. The need for ancillary medical evaluations and/or services such as ophthalmologic examinations was monitored, with subsequent follow-up to ensure receipt of services, results retrieval, and communication of results to the primary care provider.