Summary

A Clinical Practice Improvement study was conducted at six HMOs throughout the US to determine whether restrictive formulary limitations on drugs are associated with differences in health care resource utilization, including office visits, prescriptions, and hospitalizations, and whether this association varies by age. Data were collected from 13,000 patients with at least one of five diseases (arthritis, asthma, epigastric pain/ulcer, hypertension, and otitis media) at every encounter for one year.  Results show that greater limitations in drug classes were significantly associated with greater health care resource utilization and that these associations were sometimes significantly greater for elderly patients after controlling for severity of illness and other variables.

Primary Objectives

Examine whether restrictive formulary limitations on drugs are associated with differences in health care resource utilization, including office visits, prescriptions, and hospitalizations, and whether this association varies by age.

Methods

1. 13,000 patients from six HMOs throughout the US were assessed for severity of illness at every encounter for one year, totaling more than 99,000 outpatient visits, 480 emergency department visits, 1,000 hospitalizations, and 240,000 prescriptions.
   

2. Patients had at least one of five diseases (arthritis, asthma, epigastric pain/ulcer, hypertension, and otitis media).
   

3. HMO settings had various levels of formulary limitations on drugs to treat the five study diseases.
   

4. Outcome measures were prescription count and cost, office visit count, emergency department count, and hospitalization count.
   

5. Multivariate regression was used to control for other variables, including severity of illness, provider count, age, gender, and time in study.

Results

1. Greater limitations in drug class were associated significantly with greater health care resource utilization.
   

2. These associations were sometimes significantly greater for elderly patients (age > 65 years) controlling for severity of illness and other variables.
   

3. Greater limitations for the drug classes of propionic acids, immediate-release theophylline, and loop diuretics were associated with higher drug costs for elderly patients, but not for non-elderly (age < 64 years) patients.
   

4. Greater limitations for the drug class of H₂ antagonists were associated with higher total drug costs for both elderly and non-elderly patients.

Impact

Common HMO cost-containment strategies may be associated with higher severity-adjusted health care resource utilization, and in specific areas, this association is more pronounced in the elderly due to physiologic changes in older people that can affect absorption, distribution, metabolism, and elimination of medications (Amer. J. Managed Care 4:8, August 1998:1105-1113).