Diabetes Diagnosis, Resource Utilization, and Health Outcomes

Volume 14: 32-38 January 2008 Number 1

Diabetes Diagnosis, Resource Utilization, and Health Outcomes

Martin C. Gulliford, FFPH; Radoslav Latinovic, BSc; and Judith Charlton, MSc

Objective: To determine the effect of a clinical diagnosis of diabetes mellitus (DM) on healthcare utilization and health outcomes.

Study Design: Cohort study.

Methods: A total of 197 United Kingdom family practices with 4974 subjects (mean age, 62.8 years; 52.2% men) with type 2 DM and 9948 matched nondiabetic control subjects. Healthcare utilization and the occurrence of complications were estimated from 2 years before to 2 years after the first clinical diagnosis of DM.

Results: From 24 months before the DM diagnosis, primary care consultations were increased in prediagnosis cases compared with controls (relative rate [RR], 1.31; 95% confidence interval [CI], 1.27-1.35), as were emergency and hospital care consultations, hospital specialist referrals, and prescription drug items. At diagnosis of DM, utilization of all forms of healthcare was increased (RR, 4.27; 95% CI, 4.17-4.36 for primary care consultations; RR, 2.49; 95% CI, 2.46-2.52 for prescription drug items). In the quarter following diagnosis, healthcare utilization was increased for acute myocardial infarction (RR, 6.29; 95% CI, 2.69-14.73), cerebrovascular disease (RR, 5.14; 95% CI, 3.37-7.84), ischemic heart disease (RR, 3.65; 95% CI, 2.77-4.80), and peripheral nerve disorders (RR, 5.01; 95% CI, 2.81-8.95). First diagnoses of myocardial infarction, cerebrovascular disease, and peripheral nerve disorders were increased during the period from 6 months before to 6 months after diagnosis.

Conclusions: Clinical diagnosis of DM is often the end of a process leading to established complications and is associated with greatly increased utilization of care. This adds to the justification of strategies for earlier detection of hyperglycemic states.

(Am J Manag Care. 2008;14:32-38)

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Diabetes Mellitus in Managed Care: Complications and Resource Utilization

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Relationship of Hemoglobin A1C, Age of Diabetes Diagnosis, and Ethnicity to Clinical Outcomes and Medical Costs in a Computer-Simulated Cohort of Persons with Type 2 Diabetes

Impact of Poorly Controlled Hypertension on Healthcare Resource Utilization and Cost

Increasing evidence that type 2 diabetes mellitus (DM) may be prevented through lifestyle intervention¹ and drug therapy² has focused attention on events occurring before the diagnosis of type 2 DM. During the period before diagnosis, the onset of DM may be prevented or delayed in some subjects. However, there is continuing uncertainty concerning the justification for screening for type 2 DM or prediabetes.³ This uncertainty results in part from limited knowledge concerning the natural history of the period before the clinical diagnosis of DM. Studies^4-6 have used electronic patient records to evaluate healthcare utilization during this period and showed that, in subjects who are later diagnosed as having DM, utilization of primary care consultations and prescription drug items is increased from up to 5 years⁴ to 8 years⁵ before the diagnosis compared with matched control subjects who never developed DM. The finding of increased utilization of medical care before the diagnosis of DM raises questions concerning the importance of the clinical diagnosis of DM. Is the clinical diagnosis of DM an incidental event of little consequence in the course of a slowly progressive condition that is already present? Alternatively, is the diagnosis of DM associated with a transition to a state with a higher rate of occurrence of adverse DM outcomes? To answer these questions, the present study compared utilization of medical care in a cohort of subjects with DM before, during, and after the clinical diagnosis of DM. We aimed to determine how the use of healthcare resources and the incidence of adverse health events changed following the clinical diagnosis of DM.

METHODS

A retrospective cohort study was implemented. Subjects diagnosed as having DM were compared with age-matched and sex-matched control subjects with respect to the utilization of medical care before and after the diagnosis of DM. The study was implemented using The Health Improvement Network, a database containing computerized medical records from family practices in the United Kingdom.^7,8 The study was approved by the London Multi-centre Research Ethics Committee.

Practice and Patient Selection
Family practices were selected if they continuously provided data from January 1, 2001, to December 31, 2005. There were 1 283 429 patients 100 years or younger who were continuously registered with 197 family practices during this time. From this cohort, medical diagnostic codes for DM and prescriptions for oral hypoglycemic drugs or insulin were used to identify cases with DM. The DM diagnosis date was defined as the earlier of the first DM medical code or the first DM prescription date. Cases with DM were selected if their diagnosis date was between January 1, 2003, and December 31, 2003 (5635 cases), and if they were aged between 30 and 89 years at diagnosis (5091 cases). Two controls were selected for each case (matching for age, sex, and family practice) from among subjects who had never been diagnosed as having DM or prescribed oral hypoglycemic drugs or insulin. Twenty-two cases were excluded because there were insufficient matched controls. Finally, we included only 4974 patients who had never been diagnosed as having type 1 DM.

Data Analysis
For each case or control, we considered the 2 years preceding and the 2 years following the first clinical diagnosis of DM. Person-time of follow-up was divided into quarterly periods (91.3 days each) for analysis. Records were censored if subjects died or ended their registration with the practice after the diagnosis. For each subject, medical events of interest were counted by quarter. These included primary care consultations, emergency care consultations, hospital admissions, referrals to and consultations with hospital specialists (referred to as hospital specialist referrals), and prescription drug items. Emergency care consultations included urgent visits by a physician to the patient’s home and referrals or attendances at hospital accident and emergency departments. Emergency care consultations and hospital admissions were combined for presentation. The data are coded using Read code clinical terms.⁹ Medical events associated with Read codes for ischemic heart disease, acute myocardial infarction, cerebrovascular disease, and peripheral nerve disorders were identified separately. Details of the codes used are available from the author.

To avoid double counting, a maximum of 1 event of each type was counted on 1 day. The rate of occurrence of each type of event per person-year was estimated by quarter for cases and controls. The relative rates (RRs) and associated 95% confidence intervals (CIs) were estimated using random-effects Poisson regression analysis, with the identifier for each triplet of case and 2 controls as the random effect and the time at risk as included as the exposure for each subject. Models were fitted using version 9 of STATA.¹⁰ In the next stage of the analysis, medical events were counted for different conditions, and results are presented for ischemic heart disease, acute myocardial infarction, cerebrovascular disease, and peripheral nerve disorders. In condition-specific analyses, medical events were combined for primary care consultations, emergency care consultations, hospital admissions, and hospital specialist referrals. Initially, all events were considered, and then first events in subjects previously free from the diagnostic grouping were evaluated separately.

RESULTS
Data were analyzed for 4974 subjects (mean age, 62.8 years [age range, 30-89 years]; 52.2% men), drawn from 197 family practices, who were diagnosed as having type 2 DM during 2003. There were 9948 control subjects, never diagnosed as having DM, who were matched for age, sex, and family practice.

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