EXPANDING THE EVIDENCE BASE IN OUTCOMES RESEARCH: USING LINKED ELECTRONIC MEDICAL RECORDS (EMR) AND CLAIMS DATA
A CASE STUDY EXAMINING RISK FACTORS AND COSTS OF UNCONTROLLED HYPERTENSION
ISPOR 2013 WORKSHOP
Hypertension (HTN) affects 50 million people in the US and one billion people worldwide
High blood pressure (BP) is the leading attributable risk factor for death worldwide
The proportion of patients with HTN receiving pharmacologic therapy in the US increased from 59.4% in1999-2000 to 71.6% in 2007-2008
Anti-HTN treatment is associated with significant reductions in stroke, MI, and heart failure
Despite the large number of available anti-HTN drugs and sizeable body of data demonstrating their efficacy, control of HTN in the US remains poor
This study examines the risk factors and per patient healthcare costs associated with uncontrolled HTN
Background
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Source: Yoon S, Ostchega Y, Louis T. Recent trends in the prevalence of high blood pressure and it’s treatment and control, 1999-2008. NCHS Data Brief. 2010 Oct; (48): 1-8.
Identify the demographic and clinical characteristics associated with uncontrolled HTN within a commercially-insured population in the US.
Quantify the incremental costs associated with uncontrolled HTN within a commercially-insured population in the US.
Study Objectives
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Patients were required to have at least 5 BP readings during their period of health plan enrollment
The first or index reading had to be between 1/1/2008 and 7/1/2009 (BPi1)
The last reading had to be at least 6 months after the first
≥18 years of age on the index date
≥12 months of continuous health plan and pharmacy benefit enrollment prior to the index date
At least one medical claim with a diagnosis of HTN (ICD-9-CM 401.xx-405.xx) at any time prior to the index date (extending to 1/1/2004)
No evidence of cancer or pregnancy during the pre- or post- index periods
Patient Selection Criteria
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BP control was determined based on a weighted average of BP readings recorded during the follow-up period
Each reading was weighted by the number of days elapsed until the next reading
Patients assigned to BP cohorts as follows:
Controlled
Patients with Type II diabetes or CKD: SBP <130 mmHg and DBP <80 mmHg
All other patients: SBP <140 mmHg and DBP <90 mmHg
Uncontrolled
Patients with Type II diabetes or CKD: SBP ≥130 mmHg or DBP ≥80 mmHg
All other patients: SBP ≥140 mmHg or DBP ≥90 mmHg
Analytic Cohort Definitions
Study Time Periods
6 12 - MONTH PRE - INDEX PERIOD
1/1/2009 PATIENT SELECTION PERIOD (INDEX DATES)
Demographic characteristics measured as of Index Date
1/1/2010 1/1/2007
Comorbid conditions/clinical characteristics Drug treatment patterns
1/1/2008
Drug treatment patterns Healthcare utilization Healthcare costs
6/30/2011 1/1/2011
VARIABLE DURATION (≥6 MONTH) POST INDEX PERIOD -
7/1/2009 7/1/2008
Objective: to estimate the incremental cost of uncontrolled HTN relative to controlled HTN
Generalized linear regression model with log link and gamma variance functions were estimated for total cost
Variance function selected based on Park test and Akaike’s information criterion
First-order interactions were investigated and retained in the model if significant
Recycled prediction simulation was used to estimate the incremental cost
95% confidence interval around adjusted annual incremental cost was determined using a bootstrapping method with 500 iterations
Models fit to the data with the Genmod procedure in SAS 9.2
Total annual costs were adjusted for: age, gender, race,
geographic region, type of health plan, presence of capitation, months of post-index follow-up
Analysis of Adjusted Incremental Costs of
Uncontrolled HTN
Objective: assess the risk factors associated with uncontrolled HTN/not reaching BP goal post-index
Risk factors were identified using logistic regression models
with an indicator of uncontrolled BP as the outcome and a list of postulated risk factors as the covariates
Adjusted odds ratio and 95% confidence limits for uncontrolled/not at goal BP compared to controlled/at goal BP were calculated
First-order interactions were investigated and retained in the model if significant.
Goodness of fit was assessed with the Hosmer and Lemeshow test and the c statistic.
Assessment of Risk Factors Associated with HTN
Demographic and Pre-Index Clinical Characteristics
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UNCONTROLLED
N=5,061
CONTROLLED
N=12,750 p-value Demographic Characteristics
Age (Mean, SD) 59.1 12.2 57.5 12.4 <0.0001
Male (%, N) 2,287 45.2% 5,212 40.9% <0.0001
Presence of Capitation (N, %) 466 9.2% 1,147 9.0% 0.6572
Race (N, %) (from EMR) <0.0001
White 2,301 45.5% 6,327 49.6%
Black/African American 604 11.9% 975 7.6%
Asian 14 0.3% 41 0.3%
Hispanic 15 0.3% 61 0.5%
Other/Unknown 2,127 42.0% 5,346 41.9%
Days of Follow-up (Mean, SD) 790.5 310.5 826.0 297.9 <0.0001 Clinical Characteristics
Body Mass Index (Mean, SD) (from EMR) 33.6 7.8 31.8 7.1 <0.0001 No. unique 3-digit ICD-9-CM diagnosis codes (Mean, SD) 9.3 7.2 9.2 6.9 0.7462 Antihyperlipidemic medication use (N, %) 2,461 48.6% 5,697 44.7% <0.0001 No. unique antihypertensive medications (Mean, SD) 2.0 1.6 1.5 1.3 <0.0001
0.0%
10.0%
20.0%
30.0%
40.0%
50.0%
60.0%
70.0%
80.0%
90.0%
100.0%
Uncontrolled Controlled
Select Pre-Index Comorbidities by Cohort
$0
$1,000
$2,000
$3,000
$4,000
$5,000
$6,000
Uncontrolled Controlled
Unadjusted Healthcare Costs by Cohort
Adjusted*
incremental cost
Confidence limits Lower
95%
Upper 95%
BP uncontrolled vs. controlled $1,301 $536 $2,030
Adjusted Incremental Annual Healthcare Costs
* Adjusted for age, gender, race, geographic region, type of health plan, presence of capitation, months of post-index follow-up
Select Risk Factors for Uncontrolled HTN
Patient characteristic Adjusted Odds
Ratio
Lower Confidence Limit
Upper Confidence Limit
Diabetes & CKD vs. none 8.610 6.418 11.551
Diabetes, no CKD vs. none 6.882 6.226 7.607
CKD, no diabetes vs. none 4.524 3.421 5.983
Males, ages 65+ vs. Females, ages 18-44 1.904 1.512 2.396
Males, ages 55-64 vs. Females, ages 18-44 1.944 1.582 2.391
Males, ages 18-44 vs. Females, ages 18-44 1.885 1.486 2.392
Males, ages 45-54 vs. Females, ages 18-44 1.830 1.482 2.261
Black vs. White 1.678 1.454 1.937
Hypertensive heart disease 1.524 1.292 1.798
Cerebrovascular disease 1.402 1.182 1.662
Other race vs. White 1.153 1.057 1.257
2+ vs. 0 anti-HTN medications at Index 0.962 0.835 1.109
Body Mass Index (BMI) 1.020 1.014 1.026
Months of follow-up 0.988 0.984 0.992
Hyperlipidemia 0.910 0.824 1.006
Ischemic heart disease 0.856 0.747 0.980
Cardiovascular disease 0.774 0.642 0.934
Antihyperlipidemic medications 0.765 0.695 0.842
Atrial fibrillation 0.717 0.583 0.881
Log # ICD9s 0.707 0.659 0.758
Uncontrolled BP is associated with higher costs after adjustment for patient demographic characteristics
Significant risk factors for uncontrolled HTN
Demographic characteristics: race, age, and sex
Clinical characteristics: BMI, number of unique recorded ICD-9-CM diagnoses, diabetes, CKD, hypertensive heart disease
Conclusions
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Key Strengths and Limitations of Claims Data for Case Study
Strengths
Captures all medical services during period of eligibility
Objective, comprehensive information on utilization and cost
Limitations
Does not contain clinical detail such as BP and BMI
ICD-9 coding is relatively high level
Unable to ascertain whether patients diagnosed with HTN are controlled or uncontrolled
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Strengths
Detailed vitals (BP) available, collected at the point of care
Enables the examination of hypertensive patients who are controlled and uncontrolled
Longitudinal view based on repeated clinical assessments
Enables the construction of indicators incorporating multiple assessments over time
Enables the evaluation of a potential change in status over time (i.e.,
“reaching BP goal”)
Limitations
Does not contain data from the inpatient setting
Cost and reimbursement data are not captured