Andrew Lyon and associates1 point out that the Canadian Diabetes Association's new clinical guidelines may increase the burden on laboratories because of increased use of the OGTT. I would like to add that the diagnosis of diabetes is mainly initiated by family doctors, but they may be too busy to implement any screening or to follow up appropriately once diabetes has been identified.2 The burden on family practitioners to initiate mass testing and manage patients afterward (with lifestyle advice and oral therapy3,4) is potentially huge.
The prospect of targeted screening (as supported by Lyon and associates) warrants consideration. Screening tools with different predictive abilities (75% to 80% sensitivity and 50% to 76% specificity5,6) are available, which could be used anywhere in the community. These tools take into account major risk factors such as family history, exercise levels, age, body mass index, waist circumference, dietary habits, medication history and history of dysglycemia; however, they perform poorly as stand-alone tests.7
A 2- or 3-stage screening test (e.g., the combination of a questionnaire and random capillary blood glucose testing, which yields 58% sensitivity and 94% specificity8) might be a more efficient use of resources, ensuring that OGTTs are not performed unnecessarily. Other combinations of near-patient tests and scoring tools that might be used in community settings should be studied, similar to the successful assessment in local pharmacies of people at risk of hypertension.9 It would be entirely possible, using a mixture of community-based measurements such as scoring tools for diabetes risk, fasting capillary blood glucose readings and near-patient testing of hemoglobin A1c to target individuals who should undergo an OGTT. This might reduce the potential burden on both laboratories and family physicians.
Gina Agarwal Assistant Professor Department of Family Medicine McMaster University Hamilton, Ont.
References
- 1.Lyon AW, Larsen ET, Edwards AL. The impact of new guidelines for glucose tolerance testing on clinical practice and laboratory services. CMAJ 2004;171(9):1067-9. [DOI] [PMC free article] [PubMed]
- 2.Harris MI, Klein R, Wellborn TA, Knuiman MW. Onset of NIDDM occurs at least 4–7 years before clinical diagnosis. Diabetes Care 1992; 15: 815-9. [DOI] [PubMed]
- 3.Chiasson JL, Josse RG, Gomis R, Hanefeld M, Karasik A, Laakso M. Acarbose for prevention of type 2 diabetes mellitus: the STOP-NIDDM randomised trial. Lancet 2002;359(9323):2072-7. [DOI] [PubMed]
- 4.Knowler WC, Barrett-Connor E, Fowler SE, Hamman RF, Lachin JM, Walker EA, et al; Diabetes Prevention Program Research Group. Reduction in the incidence of type 2 diabetes with lifestyle and metformin. N Engl J Med 2002; 346 (6): 393-403. [DOI] [PMC free article] [PubMed]
- 5.Rolka DB, Narayan KM, Thompson TJ, Goldman D, Lindenmayer J, Alich K, et al. Performance of recommended screening tests for undiagnosed diabetes and dysglycemia. Diabetes Care 2001; 24:1899-903. [DOI] [PubMed]
- 6.Lindstrom J, Tuomilehto J. The diabetes risk score: a practical tool to predict type 2 diabetes risk. Diabetes Care 2003;26(3):725-31. [DOI] [PubMed]
- 7.Engelgau MM, Narayan KMV, Herman WH. Screening for type 2 diabetes. Diabetes Care 2000; 23(10):1563-80. [DOI] [PubMed]
- 8.Peters AL, Davidson MB, Schriger DL, Hasselblad V. A clinical approach for the diagnosis of diabetes mellitus: an analysis using glycosylated hemoglobin levels. Meta-Analysis Research Group on the Diagnosis of Diabetes Using Glycated Hemoglobin Levels [published erratum appears in JAMA 1997;277:1125]. JAMA 1996; 276: 1246-52. [PubMed]
- 9.Kaczorowski J, Karwalajtys T, Chambers L, Levitt C, Dolovich L, McDonough B, et al. Community strategies to monitor high blood pressure among older adults [abstract]. Pharmacy Practice Research Symposium; 2002 Feb 1; Toronto.