Colleen Ross

Association of online patient access to clinicians and medical records with use of clinical services.

CONTEXT Prior studies suggest that providing patients with online access to health records and e-mail communication with physicians may substitute for traditional health care services. OBJECTIVE To assess health care utilization by both users and nonusers of online access to health records before and after initiation of MyHealthManager (MHM), a patient online access system. DESIGN, SETTING, AND PARTICIPANTS Retrospective cohort study of the use of health care services by members (≥18 years old) who were continuously enrolled for at least 24 months during the study period March 2005 through June 2010 in Kaiser Permanente Colorado, a group model, integrated health care delivery system. Propensity scores (using age, sex, utilization frequencies, and chronic illnesses) were used for cohort matching. Unadjusted utilization rates were calculated for both MHM users and nonusers and were the basis for difference-of-differences analyses. We also used generalized estimating equations to compare the adjusted rates of utilization of health care services before and after online access. MAIN OUTCOME MEASURES Rates of office visits, telephone encounters, after-hours clinic visits, emergency department encounters, and hospitalizations between members with and without online access. RESULTS Comparing the unadjusted rates for use of clinical services before and after the index date between the matched cohorts, there was a significant increase in the per-member rates of office visits (0.7 per member per year; 95% CI, 0.6-0.7; P < .001) and telephone encounters (0.3 per member per year; 95% CI, 0.2-0.3; P < .001). There was also a significant increase in per-1000-member rates of after-hours clinic visits (18.7 per 1000 members per year; 95% CI, 12.8-24.3; P < .001), emergency department encounters (11.2 per 1000 members per year; 95% CI, 2.6-19.7; P = .01), and hospitalizations (19.9 per 1000 members per year; 95% CI, 14.6-25.3; P < .001) for MHM users vs nonusers. CONCLUSION Having online access to medical records and clinicians was associated with increased use of clinical services compared with group members who did not have online access.

Use of Stabilized Inverse Propensity Scores as Weights to Directly Estimate Relative Risk and Its Confidence Intervals

OBJECTIVES Inverse probability of treatment weighting (IPTW) has been used in observational studies to reduce selection bias. For estimates of the main effects to be obtained, a pseudo data set is created by weighting each subject by IPTW and analyzed with conventional regression models. Currently, variance estimation requires additional work depending on type of outcomes. Our goal is to demonstrate a statistical approach to directly obtain appropriate estimates of variance of the main effects in regression models. METHODS We carried out theoretical and simulation studies to show that the variance of the main effects estimated directly from regressions using IPTW is underestimated and that the type I error rate is higher because of the inflated sample size in the pseudo data. The robust variance estimator using IPTW often slightly overestimates the variance of the main effects. We propose to use the stabilized weights to directly estimate both the main effect and its variance from conventional regression models. RESULTS We applied the approach to a study examining the effectiveness of serum potassium monitoring in reducing hyperkalemia-associated adverse events among 27,355 diabetic patients newly prescribed with a renin-angiotensin-aldosterone system inhibitor. The incidence rate ratio (with monitoring vs. without monitoring) and confidence intervals were 0.46 (0.34, 0.61) using the stabilized weights compared with 0.46 (0.38, 0.55) using typical IPTW. CONCLUSIONS Our theoretical, simulation results and real data example demonstrate that the use of the stabilized weights in the pseudo data preserves the sample size of the original data, produces appropriate estimation of the variance of main effect, and maintains an appropriate type I error rate.

Association of Exercise Capacity on Treadmill With Future Cardiac Events in Patients Referred for Exercise Testing

BACKGROUND Little is known about the association between exercise capacity and nonfatal cardiac events in patients referred for exercise treadmill testing (ETT). Our objective was to determine the prognostic importance of exercise capacity for nonfatal cardiac events in a clinical population. METHODS A cohort study was performed of 9191 patients referred for ETT. Median follow-up was 2.7 years. Exercise capacity was quantified as the proportion of age- and sex-predicted metabolic equivalents achieved and categorized as less than 85%, 85% to 100%, and greater than 100%. Individual primary outcomes were myocardial infarction, unstable angina, and coronary revascularization. All-cause mortality was a secondary outcome. RESULTS Patients with lower exercise capacity were more likely to be female (55.38% vs 42.62%); to have comorbidities such as diabetes (23.16% vs 9.61%) and hypertension (59.43% vs 44.05%); and to have abnormal ETT findings such as chest pain on the treadmill (12.09% vs 7.63%), abnormal heart rate recovery (82.74% vs 64.13%), and abnormal chronotropic index (32.89% vs 12.20%). In multivariable analysis, including other ETT variables, lower exercise capacity (<85% of predicted) was associated with increased risk of myocardial infarction (hazard ratio [HR], 2.36; 95% confidence interval [CI], 1.55-3.60), unstable angina (HR, 2.39; 95% CI, 1.78-3.21), coronary revascularization (HR, 1.75; 95% CI, 1.46- 2.08), and all-cause mortality (HR, 2.90; 95% CI, 1.88-4.47) compared with exercise capacity greater than 100% of predicted. CONCLUSION Adjusting for patient characteristics and other ETT variables, reduced exercise capacity was associated with both nonfatal cardiovascular events and mortality in patients referred for ETT.

The prognostic importance of abnormal heart rate recovery and chronotropic response among exercise treadmill test patients

BACKGROUND Heart rate recovery (HRR) and chronotropic response to exercise (CR) each have prognostic value among patients undergoing exercise treadmill testing (ETT). However, little is known about their prognostic use in combination and in addition to the Duke Treadmill Score (DTS). METHODS We studied 9,519 outpatients undergoing ETT between 2001 and 2004. Patients were categorized by HRR and CR. The primary outcome was all-cause mortality or nonfatal myocardial infarction (MI). Cox proportional hazards modeling was used to control for demographics, clinical history, and DTS. RESULTS After multivariable adjustment for DTS and other demographic and clinical variables, patients with abnormal HRR and CR had higher rates of all-cause mortality or nonfatal MI, as compared to patients with normal HRR and CR (hazard ratio [HR] = 1.90, 95% CI 1.35-2.69). Addition of the HRR and CR to the DTS improved outcome prediction (c-statistic improved from 0.61 to 0.68). Low-risk DTS patients with abnormal HRR and CR had significantly higher rates of all-cause mortality or nonfatal MI (HR 2.59, 95% CI 1.55-4.32), compared to low-risk DTS patients with normal HRR and CR. CONCLUSIONS Abnormal HRR and CR identified ETT patients with higher rates of all-cause mortality or nonfatal MI and provided additional risk stratification among low-risk DTS patients. These results support the routine incorporation of HRR and CR in ETT reporting and suggest the need to evaluate whether further testing and/or more intensive treatment of these higher risk patients can improve outcomes.

Blood Pressure Trajectories and Associations With Treatment Intensification, Medication Adherence, and Outcomes Among Newly Diagnosed Coronary Artery Disease Patients

Background— Blood pressure (BP) control among coronary artery disease patients remains suboptimal in clinical practice, potentially due to gaps in treatment intensification and medication adherence. However, longitudinal studies evaluating these relationships and outcomes are limited. Methods and Results— We assessed BP trajectories among health maintenance organization patients with hypertension and incident coronary artery disease. BP trajectories were modeled over the year after coronary artery disease diagnosis, stratified by target BP goal. Treatment intensification (increase in BP therapies in the setting of an elevated BP), medication adherence (percentage of days covered with BP therapies), and outcomes (all-cause mortality, myocardial infarction, and revascularization) were evaluated in multivariable models: 9569 patients had a <140/90 mm Hg BP target and 12 861 had a <130/80 mm Hg BP target. Within each group, 4 trajectories were identified: good, borderline, improved, and poor control. After adjustment, increasing BP treatment intensity was significantly associated with better BP trajectories in both groups. Medication adherence had inconsistent effects. There were no significant differences in combined outcomes by BP trajectory, but among the diabetes and renal disease cohort, borderline control patients were less likely to have myocardial infarction (odds ratio, 0.61; 95% confidence interval, 0.40–0.93), and good control patients were less likely to have myocardial infarction (odds ratio, 0.53; 95% confidence interval, 0.34–0.84) or a revascularization procedure (odds ratio, 0.66; 95% confidence interval, 0.47–0.93) compared with poor control patients. Conclusions— In this health maintenance organization population, treatment intensification but not medication adherence significantly affects BP trajectories in the year after coronary artery disease diagnosis. Better BP trajectories are associated with lower rates of myocardial infarction and revascularization.

Gender differences in the prognostic value of exercise treadmill test characteristics

BACKGROUND Although exercise treadmill testing (ETT) is less sensitive and specific for diagnosis of coronary disease in women, little is known about gender differences in the prognostic importance of ETT variables. METHODS We studied 9,569 consecutive patients (46.8% women) referred for ETT between July 2001 and June 2004 in a community-based system. We assessed the association between ETT variables (exercise capacity, symptoms, ST-segment deviations, heart rate recovery, and chronotropic response) and time to all-cause death and myocardial infarction (MI), adjusting for patient and stress test characteristics. Models were stratified by gender to determine the relationship between ETT variables and outcomes. RESULTS In the entire population, exercise capacity and heart rate recovery were significantly associated with all-cause death, whereas exercise capacity, chest pain, and ST-segment deviations were significantly associated with subsequent MI. The relationship between ETT variables and outcomes were similar between men and women, except for abnormal exercise capacity, which had a significantly stronger association with death in men (men: hazard ratio [HR] 2.89 and 95% CI 1.89-4.44, women: HR 0.99 and 95% CI 0.52-1.93, and interaction P = .01), and chronotropic incompetence, which had a significantly stronger relationship with MI in women (men: HR 1.29 and 95% CI 0.74-2.20, women: HR 2.79 and 95% CI 0.94-8.27, and interaction P = .04). CONCLUSIONS Although many traditional ETT variables had similar prognostic value in both men and women, exercise capacity was more prognostically important in men, and chronotropic incompetence was more important in women. Future studies should confirm these findings in additional populations.

The relationship between gender and clinical management after exercise stress testing.

BACKGROUND Controversy remains regarding whether gender differences exist in clinical management after exercise treadmill testing (ETT). METHODS We studied 7,506 patients (49.8% women) without documented coronary heart disease referred for ETT from July 2001 to June 2004 in a community-based setting. We assessed the relationship between gender and subsequent diagnostic testing (secondary stress testing or coronary angiography) within 6 months after ETT. Secondary outcomes included subsequent stress testing, coronary angiography, and new cardiology visits in the 6-month interval. Multivariable analyses assessed the relationship between gender and these outcomes adjusting for demographic, clinical, and stress test characteristics. In subsequent analyses, patients were stratified by Duke Treadmill Scores (Duke University, Durham, NC). RESULTS Compared with men, women referred for ETT were older, had a higher prevalence of some cardiac risk factors, achieved lower peak workloads, and, more often, experienced chest pain or ST-segment changes. After accounting for differences in clinical and ETT parameters, gender was not associated with any subsequent diagnostic testing in the 6 months after ETT (OR 1.0, 95% CI 0.85-1.18). In secondary analyses, women were less likely to undergo angiography (OR 0.63, 95% CI 0.47-0.83) with a trend toward more subsequent stress testing. Stratified analyses revealed less subsequent testing in high-to-intermediate Duke Treadmill Score women compared with men (OR 0.61, 95% CI 0.48-0.79). Women and men were equally likely to die (hazards ratio 0.93, 95% CI 0.61-1.44) in the adjusted survival analysis. CONCLUSIONS Overall, women and men equally underwent subsequent diagnostic testing after ETT. Although women were less likely to undergo angiography and higher-risk women were less likely to undergo subsequent testing, adverse events were not higher in women. Given these findings, assumptions regarding gender disparities in clinical management after ETT should be reevaluated in other settings.

Impaired heart rate recovery is associated with new-onset atrial fibrillation: a prospective cohort study.

BackgroundAutonomic dysfunction appears to play a significant role in the development of atrial fibrillation (AF), and impaired heart rate recovery (HRR) during exercise treadmill testing (ETT) is a known marker for autonomic dysfunction. However, whether impaired HRR is associated with incident AF is unknown. We studied the association of impaired HRR with the development of incident AF, after controlling for demographic and clinical confounders.MethodsWe studied 8236 patients referred for ETT between 2001 and 2004, and without a prior history of AF. Patients were categorized by normal or impaired HRR on ETT. The primary outcome was the development of AF. Cox proportional hazards modeling was used to control for demographic and clinical characteristics. Secondary analyses exploring a continuous relationship between impaired HRR and AF, and exploring interactions between cardiac medication use, HRR, and AF were also conducted.ResultsAfter adjustment, patients with impaired HRR were more likely to develop AF than patients with normal HRR (HR 1.43, 95% confidence interval (CI) 1.06, 1.93). In addition, there was a linear trend between impaired HRR and AF (HR 1.05 for each decreasing BPM in HRR, 95% CI 0.99, 1.11). No interactions between cardiac medications, HRR, and AF were noted.ConclusionPatients with impaired HRR on ETT were more likely to develop new-onset AF, as compared to patients with normal HRR. These findings support the hypothesis that autonomic dysfunction mediates the development of AF, and suggest that interventions known to improve HRR, such as exercise training, may delay or prevent AF.

Trivalent Inactivated Influenza Vaccine Is Not Associated With Sickle Cell Crises in Children

Background and Objectives: Children with sickle cell disease are considered at high risk for complications from influenza infection and are recommended to receive annual influenza vaccination. However, data on the safety of influenza vaccination in children with sickle cell anemia are sparse. Methods: Using a retrospective cohort of children aged 6 months to 17 years in 8 managed care organizations that comprise the Vaccine Safety Datalink and who had a diagnosis of sickle cell anemia from 1999 to 2006, we conducted matched case-control and self-controlled case series studies to examine the association of trivalent inactivated influenza vaccination with hospitalization for sickle cell crisis in the 2 weeks after vaccination. Results: From an original pool of 1085 pediatric subjects with a diagnosis of sickle cell anemia, we identified 179 children with at least 1 sickle cell crisis during any influenza season (October 1–March 31). In the matched case-control study (matching on age category, gender, Vaccine Safety Datalink site, and season), the odds ratio of hospitalization for a crisis in vaccinated compared with unvaccinated children was not significant: 1.3 (95% confidence interval 0.8–2.2). In the self-controlled case series study of hospitalized cases, the incident rate ratio for hospitalization with sickle cell crisis in the 2 weeks after trivalent inactivated influenza vaccination was also not significant: 1.2 (95% confidence interval 0.75–1.95). Conclusions: This large cohort study did not find an association of influenza vaccination and hospitalization for sickle cell crises in children with sickle cell anemia.

Increasingly restrictive definitions of hyperkalemia outcomes in a database study: effect on incidence estimates.

To determine the incidence of hyperkalemia‐associated adverse outcomes among ambulatory patients with diabetes newly initiating renin‐angiotensin‐aldosterone system (RAAS) inhibitor therapy and to examine to what extent increasingly restrictive definitions of hyperkalemia‐associated outcomes influenced incidence estimates.