Early Identification of Type 2 Diabetes

More than 60% of the estimated 285 million people with diabetes globally are in lowand middleincome countries (LMICs) (1). Largely driven by the growth of type 2 diabetes, the numbers of people with diabetes worldwide is projected to touch at least 450 million by 2030, with the biggest increase happening in LMICs and substantially driven by populous Asian countries like India and China (1). Recent data indicate an urban diabetes age-standardized prevalence of 11.4% in China (2) and 9.1–13.0% in India in the ongoing Indian Council of Medical Research–India Diabetes (ICMR–INDIAB) study (V.M. Anjana, A. Mohan, personal communication). Furthermore, the prevalence of diabetes may be as high as 8.2% among rural residents in China (2) and may vary from 2.8 to 11.9% in rural India, depending on the level of economic development (ICMR– INDIAB study). Importantly, a high proportion of people with type 2 diabetes (50– 70% in China [2,3] and 30–80% in India [ICMR–INDIAB study]) remain undiagnosed and thus untreated. Should there, therefore, be an active policy to identify dysglycemia and diabetes early? As undiagnosed diabetes is frequently associated with potentially preventable costly diabetes complications and concomitant cardiovascular risk factors (4– 6), a policy of early identification through systematic or opportunistic means may have some appeal. Indeed, the merits or otherwise of a screening policy for diabetes have been previously reviewed and assessed (7). The consensus thus far has been that type 2 diabetes meets many of criteria for screening, namely, the burden is large, the natural history is well understood, there is a long latent period, and effective and cost-effective treatments for diabetes are available. However, three challenges still remain: 1) a reliable, highperformance, convenient, low-cost screening test that can be universally applied has been lacking; 2) direct evidence of the benefits and costs of screening are hard to obtain; and 3) the capacity of health systems worldwide, especially in LMICs, to carry out identification and then to manage the potentially huge new burden of newly identified cases is a concern. The challenge of a reliable, convenient, low-cost test that may be used widely, especially in LMICs, is potentially soluble. Ritchie el al. (8), for example, present data in this month’s issue of Diabetes Care indicating that a point-of-care (POC) blood test could be a simple and reliable tool for identifying undiagnosed diabetes. In a population-based study in resource-poor rural South India, Ritchie el al. (8) evaluated a finger-prick fasting capillary POC against fasting venous plasma glucose by systematically screening a random sample of 1,085 participants aged 30 years and older, representing a population of 75,089 from 20 villages. Diabetes was defined according to the 1999 World Health Organization (WHO) criteria of fasting venous plasma glucose of 126 mg/dl. They found that the POC fasting capillary test that they used had an area under the curve of 0.87 for detecting diabetes and was significantly better than risk scoring tools that use common clinical variables (age, BMI, hypertension, waist circumference, area under the curve of 0.69). Furthermore, adding clinical variables to their POC fasting capillary test did not significantly improve the discriminatory capability beyond that achieved with the POC glucose alone. An oral glucose tolerance test or fasting plasma glucose are cumbersome and inconvenient, and the A1C test is expensive and poses special problems with standardization and performance. All of these tests are complex and require skilled health care workers and laboratory facilities for the analysis of samples, which are often a challenge in resourcepoor settings. While there have been numerous attempts to develop simple paper and pencil tests to screen for diabetes, these have remained suboptimal, and their performance varies widely by population (9). Therefore, as suggested by WHO, a simple and reliable POC capillary glucose test offers major advantages, but its cost and cost-effectiveness are yet to be ascertained (10). These results from Ritchie et al. add to the literature on POC capillary glucose tests in resource-poor settings (11,12). While data from Ritchie et al. (8) indicate a realistic potential to develop reliable and convenient low-cost POC tests to detect diabetes, three issues remain to be resolved. Firstly, the performance of capillary POC tests may differ by population characteristics or disease prevalence. For example, POC glucose performed well for detecting diabetes in an Australian indigenous population, but was less discriminatory in a study among Maori (11,12). Further investigations into evaluating a variety of cut points for capillary POC tests in diverse populations may help. Secondly, the costs of POC tests for mass application in LMICs remain a major concern. Ritchie et al. indicate that the POC capillary test, at less than $2 (U.S.) per test, may be inexpensive, but the cost of these tests may need to be many-fold lower before they can be considered for broader use in LMICs. Partnerships with manufacturers in developing countries may help to lower the costs as has been done with cervical cancer tests and with vaccines (13,14). Thirdly, how a POC blood test may be combined with cheaper paper and pencil risk scores remains to be fully explored. While Ritchie et al. (8) point out that their POC capillary test is better than India-specific risk scores, the latter are only a first step to improve the cost-effectiveness of the identification of undiagnosed diabetes. Given the ethical and logistical challenges of conducting a randomized controlled trial comparing a screening policy versus control, direct evidence for the benefits and costs of screening for diabetes is unlikely to be produced. Recently, however, a number of studies indicate that a policy of early identification of type 2 diabetes may be worth seriously considering. The Anglo-Danish-Dutch study of Intensive Treatment In peOple with screeN-detected diabetes in primary care (ADDITION) trial, whose results were recently reported at an international conference (15), found that primary-care stepwise screening for type 2 diabetes is feasible in settings with good infrastructure and can identify people with E d i t o r i a l s