Dewey C. Scheid, MD, MPH Laine H. McCarthy, MLIS Frank H. Lawler, MD, MSPH Robert M. Hamm, PhD Kathryn E.H. Reilly, MD, MPH Oklahoma City, Oklahoma Submitted, revised, April 16, 2001. From the Department of Family and Preventive Medicine, University of Oklahoma Health Sciences Center. Reprint requests should be addressed to Laine H. McCarthy, 900 NE 10th Street, Oklahoma City, OK 73104. E-mail: laine-mccarthy@ouhsc.edu.
References
Semiquantitative MA tests are not favored by the ADA8 but have an accuracy similar to quantitative tests. Though they may not be reliable when used by untrained health care providers, high sensitivities and specificities can be obtained by personnel other than laboratory technicians.34 Semiquantitative tests have the important advantages of increased convenience and decreased cost, which may improve adherence to recommendations. Several authors have suggested that semiquantitative MA tests could at least substitute for the first quantitative test in a multiple test strategy,28,36,45,66 and the ADA position has recently shifted to allow semiquantitative tests if quantitative tests are not readily available.67
The Micral is the best studied test, appears reliable, and has a high sensitivity even at low UAC (20 mg/L). A pooled analysis of 10 previous studies of the Micral found a sensitivity of 92.3% and a specificity of 83.2%.68 Results from studies were included that investigated 24-hour urine samples; homogeneity among the studies was not tested. Two large studies found a sensitivity of 90.1% to 96.7% and a specificity of 71% to 87%.42,51 The Micro-Bumintest has good sensitivity but has been evaluated at a slightly higher cutoff UAC (30 mg/L), and the reliability has been questioned.47,52,53
MA screening clearly meets only 4 of the 6 criteria of Frame and Carlson. Current recommendations for MA screening require repeated testing that is onerous and probably does not improve diagnostic certainty. This strategy has not been compared with simpler strategies in a randomized controlled trial. In our analysis, at low prevalence the theoretical improvement in specificity is minimal and would not seem to justify the need for a criterion of 2 of 3 tests positive.
A number of studies have reported on the poor rate of screening persons with diabetes in primary care.69,70 In an academic family medicine center, Lawler and Viviani71 found that the patient-reported rate of MA screening was 43%. In a recent survey of primary care physicians, more than 40% reported screening no persons with type 2 diabetes for MA, and only 17% screened more than 50% of persons with type 1 diabetes.72 A recent analysis of insurance claims data for 4623 persons with diabetes found that only 2.1% of those without known nephropathy were tested for MA during the study year.73 This lack of adherence to even single annual screening tests raises questions of whether the screening strategy of repeated screening followed by treatment will effectively prevent diabetic nephropathy. Strategies that incorporate using a semiquantitative test first may mitigate adherence problems, but the feasibility of such strategies has not been evaluated. A practice-based trial comparing screening strategies is needed.
Because of the high incidence of nephropathy and ESRD, MA screening in patients with type 1 diabetes is probably cost-effective. Screening persons with type 2 diabetes for MA is less certain. Analyses have generally not considered imperfect testing or the impact of sequential testing strategies. Based on studies that have demonstrated delayed progression in persons with diabetes who have normoalbuminuria,74 3 cost-effectiveness analyses found that routine use of ACEIs compared favorably with MA screening.58,62,64 A cost-effective analysis that considered recommended testing strategies and imperfect screening would be useful.
MA is associated with a substantial risk of cardiovascular events.75 The recent Heart Outcomes Prevention Evaluation Study found that ACEIs lower the risk of death, heart attack, stroke, and other complications of diabetes mellitus in high-risk patients with known cardiovascular disease.76,77 Given the difficulties of changing patient and health provider behavior, a more compelling question, which we discuss in a subsequent article, is whether routinely prescribing ACEIs is more desirable than annual screening and treatment when MA is detected.
Acknowledgments
We would like to thank the many people who contributed their time reading and commenting on our manuscript. We also thank Alice Reed and Stacy Wigley for their help assembling and managing the reference databases for this review and for preparing some of the graphics.
