OBJECTIVE: To determine the value of using risk factors to decide which patients should undergo serum screening for type 2 diabetes.
SEARCH STRATEGIES: The MEDLINE and EMBASE electronic databases were searched for original studies of screening for type 2 diabetes on the basis of risk factors. The reference lists of all reviews, letters, editorials, consensus statements, and guidelines for diabetes screening were searched for additional studies. The Cochrane database was also searched for relevant reviews.
SELECTION CRITERIA: All original studies regarding selective serum screening for type 2 diabetes on the basis of risk factors were included.
MAIN RESULTS: Seven studies were selected for review. Three studies were cross-sectional in design; 3 employed survey data to develop computerized statistical models that used risk factors to identify cases of type 2 diabetes; and 1 used a similar method, but the resulting model was field tested in a separate population. No study describes a risk-factor-based method or instrument that helps substantially in the diagnosis of type 2 diabetes.
CONCLUSIONS: Selective screening for type 2 diabetes on the basis of risk factors cannot be recommended. Serum screening can be offered to patients who present with typical symptoms of diabetes.
Diabetes is responsible for half of all nontraumatic amputations, 15% of blindness, and more than a third of all end-stage renal disease. The costs attributed to this disease total more than $100 billion annually.1
Identifying new patients with diabetes has always been a challenge. The third National Health and Nutrition Examination Survey (NHANES III)2 revealed that roughly 35% of the people with type 2 diabetes remains undiagnosed. This suggests that universal screening might be prudent. Several studies, however, have shown that the yield from universal serum screening in specific populations is low.3-5 Because of this low yield and because the risk factors for type 2 diabetes are well known Table 1, selective serum screening on the basis of risk factors is widely recommended.6-10
The goal of this paper was to determine the usefulness of the assessment of risk factors as a tool to decide who should undergo serum screening. Different investigators and organizations use slightly different serum tests and definitions to rule out or confirm the presence of type 2 diabetes. This paper does not address the performance of different blood tests (eg, fasting blood glucose, oral glucose tolerance test) or different definitions of type 2 diabetes.
Methods
The MEDLINE and EMBASE electronic databases were searched for the years 1966 to 1998, using the medical subject headings “diabetes mellitus” and “mass screening.” The search was then limited to English language papers dealing with human subjects. Resulting sets were combined. Titles of all papers in the combined set for each database were surveyed. Original studies, regardless of design, that deal specifically with the use of risk factors to screen and identify patients with type 2 diabetes were included. Reference lists of all publications including original studies, letters, commentaries, guidelines, and reviews were surveyed for relevant original studies. The Cochrane Database of Systematic Reviews was searched for relevant reviews.
Selected studies were assessed for validity using the “Users’ Guide to the Medical Literature.”11 The results of all studies were reviewed, regardless of shortcomings in validity Table 2.
Results
A total of 346 citations were retrieved from MEDLINE by combining the sets for “diabetes mellitus” and “mass screening” and limiting the search to English language papers dealing with human subjects. Review of the titles revealed 23 papers that specifically addressed the strategy of serum screening on the basis of risk factors. All 23 were retrieved; 7 were original studies. Searches of the EMBASE database, The Cochrane Database of Systematic Reviews, and reference lists of all papers did not yield additional studies.
Three of the 7 studies were cross-sectional in design. Three other studies used data from health surveys to develop computerized models designed to predict the presence of diabetes on the basis of risk factors. The final study used a similar design, but the resulting model was then tested in a population different from that in which it was developed.
Four of the studies used a combination of risk factors and symptoms of diabetes (eg, polyuria). The use of symptoms in combination with risk factors does not precisely fit the question addressed by this paper. So few studies address the use of risk factors alone, however, that these studies were also included. Table 3 provides a summary of the results.
Cross-Sectional Studies
Duncan, Linville, and Clement12 measured the risk factors and blood glucose levels of 575 self-selected participants in a screening program to test the strategy recommended by the American Diabetes Association (ADA)6 of screening only those patients with 1 or more risk factors for diabetes. It is unknown whether blood glucose levels were measured by independent blind investigators without knowledge of each patient’s risk factors. The authors describe blood glucose test results only as “normal” or “abnormal.” It is not specified whether fasting or random blood glucose levels were used and what level was considered abnormal or diagnostic of diabetes. The demographic characteristics of the patients were not described. Blood glucose testing was done on all subjects, regardless of whether risk factors were present. Only patients with abnormal results were followed up to determine which of them were eventually diagnosed with type 2 diabetes. The validity of this study, therefore, is questionable, as the standards used for abnormal and normal blood glucose levels and the characteristics of the patients studied are unclear.