Use of Microalbuminuria Testing in Persons with Type 2 Diabetes: Are the Right Patients Being Tested?
Discussion
Our data suggest that several problems exist in the use and interpretation of microalbuminuria testing in the primary care setting. First, microalbuminuria testing is being performed on only 1 of 5 adult patients with type 2 diabetes. Second, in this practice, testing is not targeted to the patients who are most likely to benefit from the results. Rather, the tests seemed to be used indiscriminately. Finally, even when patients are screened and found to have microalbuminuria, only a small percentage were started on appropriate therapy. At least in this patient population, it appears that ACEI or ARB therapy is reserved for patients with higher blood pressures rather than used for renal protection.
The observation that patients with existing proteinuria or who were on ACEI or ARB therapy were screened just as often as those who were prime candidates for screening contradicts our initial hypothesis. We had assumed that clinicians would not screen patients who were on ACEI or ARB therapy, reducing the overall screening rate. Apparently, this is not the case. At least in this practice, a low screening rate is not due to selective screening.
The lack of optimal use of microalbuminuria testing and the failure to respond appropriately to positive test results suggests that current recommendations have not been embraced by physicians. Also, the complexity of carrying out these recommendations may make it difficult to integrate this screening into routine practice. If the current evidence on ACEI and ARB therapy for the prevention of renal dysfunction is to be translated into practice, either greater emphasis needs to be placed on microalbuminuria screening or more efficient ways to provide renal protection for patients with diabetes should be considered. Other studies have found that between 17% and 30% of patients with type 2 diabetes have microalbuminuria.1,12,13 Although primary care physicians report that they provide microalbuminuria screening to a large percentage of their patients with diabetes, in fact only a small percentage of those who should be screened actually are screened.10 Suboptimal screening rates for important conditions seen in primary care are not unique for microalbuminuria. Other studies have documented comparable low screening rates for a wide variety of cancers.14 Since physicians do not screen reliably for potentially fatal diseases with screening modalities that have been available for decades, it is unlikely that their behavior is likely to improve when asked to screen for microalbuminuria.
Also, recent evidence that ACEI therapy may improve endothelial function in patients with type 2 diabetes suggests that even patients without microalbuminuria may benefit from routine ACEI therapy.15 Other studies suggest that routine use of ACEIs in middle-aged patients with type 2 diabetes may provide substantial benefits at only modest costs compared with a screening strategy.16 These data suggest that a more effective strategy would be to advise that all patients with type 2 diabetes start ACEI or ARB therapy along with their medications for diabetes. This strategy would obviate the need for microalbuminuria screening, while assuring that patients receive any additional benefits of ACEI or ARB therapy unrelated to renal protection. However, using this strategy, patients who may not have proteinuria will have to take the medication for a prolonged period, pay for it, and run the risks for any complications associated with using the drug.
Limitations
Our study has several limitations. Only 1 practice was examined, and it was part of a residency training practice. This means that less-experienced clinicians were providing care that could reduce the overall rate of screening. However, the rate of screening observed in this study was very similar to rates found in the practices of clinicians with more experience,11,12 suggesting that the lack of experience of resident physicians may be balanced by the oversight provided by faculty preceptors.
Another limitation is that it was not possible to account for microalbuminuria screening completed outside the MUSC medical center. Patients who split their care among several providers could have had testing performed in other health care facilities. However, since more than 95% of the referrals from the MUSC Family Medicine Center stay within the university health care system, it is doubtful that many patients would have received testing outside the search capabilities of the hospital laboratory database.
Finally, the study was limited in its power to detect small differences between the groups. We originally conceived our project as an exploratory study to determine how many patients were already taking ACEIs and the potential effect of this on overall screening rates for microalbuminuria. Without any reference for the percentage of patients who were taking ACEIs, we could not perform an ad hoc power analysis. However, a post hoc analysis shows that for a sample in which the groups are matched in a 1-to-3 ratio (approximating the proportion of the 51 patients in our sample taking ACEIs and the 183 not taking these drugs) and given the study sample size, our study had a power of 80% to detect a difference in screening rates between 20% in the baseline group and 5% in the ACE or ARB groups. The actual difference seen in our study was much smaller, which increases the possibility of a type II error.
