Ap Yu

Estimating the Effect of Medication Adherence on Health Outcomes among Patients with Type 2 Diabetes—An Application of Marginal Structural Models

OBJECTIVE We applied marginal structural models (MSMs) to estimate the effects of medication adherence with hypoglycemics on reducing the risk of microvascular complications in type 2 diabetic patients. METHODS A retrospective longitudinal cohort study for type 2 diabetes patients was conducted using the California Medicaid claims database (1995-2002). Medication adherence and multiple time-varying confounders were measured quarterly over a maximum of 7.5 years follow-up. Cox regression models and MSMs results on the effect of compliance were compared. RESULTS Of 4708 eligible patients, 2644 (56.2%) experienced microvascular complications during the follow-up period. After controlling for baseline covariates, standard Cox models estimated that adherence was associated with increased risk of complication with hazard ratio (HR) of 1.09 (95% confidence interval (CI): 1.00, 1.18). With adjustment of time-varying confounders as exogenous variables, the HR was 0.96 (0.88, 1.04). Using the MSM technique, the HR was 0.76 (95% bootstrap CI: 0.60, 0.92), indicating a significant benefit of medication adherence with hypoglycemics on the reduction of microvascular complications. This result contrasts with the negative results obtained in the hazard model, and is more consistent with prior clinical trial results CONCLUSION Unlike conventional models, MSMs estimated that higher medication adherence may result in reduced risk of microvascular complications among patients with type 2 diabetes.

Investigating differential item functioning by chronic diseases in the SF-36 health survey : A latent trait analysis using MIMIC models

Objectives: Differential item functioning (DIF) is present when respondents of unique subgroups endorse certain items differently given the respondents have the same underlying ability. This study investigates the presence of DIF regarding chronic illnesses among items of the physical functioning (PF) and mental health (MH) domains of the SF-36 health survey. Methods: Multiple indicators multiple causes (MIMIC) model was applied to data extracted from the Kaiser Permanente database for members who completed the SF-36 during 1994–1995 (N = 7538). DIF effects were evaluated for sociodemographic variables and for indicators of 5 chronic conditions: hypertension, rheumatic conditions, diabetes, respiratory diseases, and depression. An iterative strategy with backward selection was applied to build DIF models, which were estimated by weighted least squares. The Hochberg procedure was applied to P values for multiple tests. Results: After controlling for the selected covariates and the latent ability, DIF was present in 3 items for hypertension, one for respiratory diseases, and one for diabetes. Adjusting for DIF did not modify the overall pattern of exogenous variables’ effects on PF or MH, except Hispanic and other ethnicity on PF, education on MH became insignificant; and black ethnicity on PF, old ages and other ethnicity on MH became significant. Conclusions: Considering the number of items and disease subgroups compared, the presence of DIF was minimal among items of the PF and MH domains of the SF-36. DIF had little effect on comparisons of sociodemographic or disease groups.

AD2: MEDICATION TREATMENT PERSISTENCE OF OVERACTIVE BLADDER/URINARY INCONTINENCE PATIENTS IN A CALIFORNIA MEDICAID PROGRAM AND THE BENEFIT OF THEIR REFILL ADHERENCE ON URINARY TRACK INFECTION

costs. In this model, prescription non-procurement was more likely to be reported in the Medicare-only population (OR: 1.47; 95% CI 1.46–1.48) and in the Medicare plus Medicaid population (OR: 1.11; 95% CI 1.10–1.12) as compared to respondents with Medicare plus private insurance coverage. CONCLUSIONS: Significantly different rates of persons who forego filling a prescription for cost reasons were observed among Medicare beneficiaries. More vulnerable groups of seniors were identified. Dual eligible Medicare/Medicaid enrollees and those with Medicare alone are more likely to restrict medication procurement due to cost.

PRK5: ANALYSIS OF COMORBIDITY, HOSPITAL UTILIZATION AND COST OF OVERACTIVE BLADDER IN A CALIFORNIA MEDICAID PROGRAM—A CASE-CONTROL STUDY

OBJECTIVES: To explore the possible comorbidities associated with Overactive Bladder (OAB), and to estimate the resource utilization pattern and cost of OAB in a Medicaid population. METHODS: A retrospective case-control matching study was performed. Five thousand five hundred seven continuously enrolled Medi-Cal patients who were diagnosed with OAB and received OAB prescriptions from 1999 to 2001 were 1 :2 matched based on age, gender, race, and residence county. Annual hospital utilization and cost were calculated for both OAB and matched control cohorts, and prevalence ratios (PR, OAB over control) for 34 ICD-9 based comorbidity measures from AHRQ were examined. RESULTS: Out of 34 comorbidities, 13 occurred in OAB patients at least twice as much as in general Medicaid population: paralysis (PR = 10.46), urinary track infection (UTI, PR = 3.74), other neurological (PR = 2.79), peripheral vascular disorder (PR = 2.42), valvular disease (PR = 2.32), arrhythmias (PR = 2.31), atopic dermatitis (PR = 2.19), blood loss anemia (PR = 2.14), depression (PR = 2.10), pulmonary circulation disorder (PR = 2.10), hypothyroidism (PR = 2.08), peptic ulcer disease including bleeding (PR = 2.08), and deficiency anemias (PR = 2.05). Among these diagnoses, obesity, UTI, dermatitis and depression are known comorbidities related to OAB. OAB patients had much higher annual resource utilization than the matched control group: physician office encounters (27.39 vs. 2.70, P < 0.0001), and an emergency room visits (0.26 vs. 0.04, P < 0.0001). OAB patients had approximately two-fold higher costs than the control cohort for pharmacy and medical services:

Persistence and Adherence of Medications for Chronic Overactive Bladder/Urinary Incontinence in the California Medicaid Program

3319.85 vs.

Delay in Filling the Initial Prescription for a Statin: A Potential Early Indicator of Medication Nonpersistence

1560.06 (P < 0.0001),

PMC33 BRIDGING BEYOND REGRESSION-ARTIFICIAL NEURAL NETWORK IN MAPPING FROM SF-36 TO HEALTH UTILITY

4754.86 vs.

PRK1: COMPARISON OF DIRECT HEALTH-CARE COST, HOSPITAL UTILIZATION AND MEDICATION PERSISTENCE BETWEEN EXTENDED RELEASE FORMS (ER) OF TOLTERODINE AND OXYBUTYNIN IN OVERACTIVE BLADDER/URINARY INCONTINENCE PATIENTS

2592.68 (P < 0.0001). CONCLUSIONS: OAB patients who received drug treatment incurred a heavy economic and resource burden to the California Medicaid program. Comorbid conditions were much more prevalent in the OAB cohort than in the general Medicaid population.