In this highly adherent cohort of adults with diabetes and hypertension, failure to intensify treatment for high blood pressure was a common problem: primary care providers intensified treatment at only 13% of visits where blood pressure was unequivocally elevated. As hypothesized, a variety of modifiable visit-related factors appeared to influence the decision to intensify antihypertensive treatment. Providers were more likely to intensify treatment at routine visits and with their regular patients, but less likely to do so in the setting of coronary heart disease, or an elevated capillary glucose. When providers decided to intensify treatment, they also tended to make a diabetes-related referral, and perform a capillary glucose.
The main strength of our study was the availability of detail at the level of the individual clinic visit, made possible by rigorous, standardized data abstraction from medical records linked to all available electronic databases. Unlike most previous studies, this detail allowed us to investigate specific modifiable visit-based factors.
Nonetheless, several limitations should be considered when interpreting these results. First, because we used pharmacy records to identify intensification, we likely missed some episodes when the provider recommended intensification but the patient declined or significantly delayed filling the prescription. However, our patient population was otherwise highly adherent and the intensification rate we observed of 13% was similar to the rates in other studies (range 4–38%).9,15,16,23,24
Second, our data were collected from 1998 to 2001 and may not be fully generalizable to the present day. Systems changes including electronic medical record availability may impact some of the associations reported, such as the decreased intensification by the primary care provider when the patient was co-managed by a cardiologist. However, in a recent qualitative study,23
co-management was listed as a barrier to intensification. Physician rates of intensification are also still quite low (13–35%) in 2 recently conducted qualitative studies.9,23
Also, our choice of patients from a single managed care provider enhanced convenience at the possible expense of generalizability. However, our study sample was racially diverse, included men and women, who saw multiple providers at 17 different clinic sites.
Third, many of the visit-based factors were based on medical record review. Although we attempted to evaluate all clinical variables at the visit that could impact intensification by the provider, we were unable to capture everything. We may have missed instances where a patient brought a log of blood pressure readings from the home if the provider did not record this in the medical record. In addition, if a physician did not record anything related to prescription side effects in the medical record, then we coded this as no side effects. This potential for misclassification along with the low rate of intensification may have biased some of these items toward the null of no significant effects (i.e., type II error). For instance, patient volume was not significantly associated with lack of intensification, yet a suggestion of an association was noted when patient volume exceeded 20 patients per provider. We only had 50% power to detect this difference as intensification occurred rarely; therefore, we were unable to conclusively state that physician workload does not effect intensification. Finally, we were unable to assess some relevant provider characteristics such as knowledge, beliefs, and attitudes about diabetes and antihypertensive therapy.
Since 1980, at least 3 studies have evaluated visit-based factors associated with intensification of antihypertensive patients without diabetes,15–17
and 1 study evaluated visit-based factors in antihypertensive patients with diabetes.9
These 4 studies found that higher systolic and diastolic blood pressures at the visit were associated with treatment intensification by the provider.9,15–17
Berlowitz et al. found that having a routine visit was associated with decisions to intensify treatment.15
The 3 studies that evaluated patient demographics found no significant association between patient demographics and intensification of antihypertensive therapy.9,15,17
Two studies evaluated provider type and found no significant associations between provider type and treatment intensification.9,15
These results are consistent with our findings.
In contrast to previous studies, we had access to more data at the level of the individual visit. These data yielded several novel observations. Providers that intensified antihypertensive treatment were more likely to order a diabetes-related referral, or perform a capillary blood glucose at the visit. An elevated capillary glucose was 1 barrier to intensification of antihypertensive medications even after adjusting for blood pressure and age. The average serum glucose in visits reporting a fingerstick was 174 mg/dL, suggesting that the provider may have been focusing on diabetes management instead of blood pressure management. Berlowitz et al, in an analysis of 274 diabetic hypertensive patients, did not find an association between intensification of diabetes medications and lack of intensification of antihypertensive medications. He concluded that providers were not being distracted by diabetes management,24
yet our results suggest the opposite. In a survey of primary care providers, Hicks et al. found that competing demands was the second major reason providers reported for not intensifying antihypertensive medications at hypertensive visits.9
This supports our finding related to glucose management being the focus of some visits. Primary care providers working to manage multiple concurrent problems may choose to optimize therapy of only a limited number of conditions at 1 time.
Unexpectedly, we found that a diagnosis of coronary heart disease was a strong barrier to intensification in our study. Berlowitz et al., in their analysis of 274 patients with diabetes and hypertension, found a similar but statistically ambiguous association between coronary artery disease and lack of intensification.24
Cotton et al. recently reported that providers listed co-management with a cardiologist or nephrologist as a reason for lack of intensification, as primary care providers were unsure of their role.23
In our study, many patients with coronary heart disease were under co-management by a cardiologist, but the cardiologist frequently failed to intensify blood pressure medications. There appeared to be little or no coordination of decision-making with the primary care provider. Several studies show improved quality of care outcomes with the use of care management systems including a patient care coordinator.25,26
In summary, our findings suggest 2 potential complementary approaches to improve treatment intensification for elevated blood pressure in adults with diabetes. First, clinics could promote continuity of care by scheduling routine appointments with a patient’s usual care provider at which blood pressure control would be an explicit focus. Second, cardiologists and primary care providers could organize to improve co-management and communication related to treatment intensification. Given the overall low rate of intensification, however, we may need to think of other creative ways to solve this substantial health problem. By targeting intensification at more than 1 level, we may improve clinical outcomes for patients with significant risks for complications from hypertension.