Hospital utilization by health maintenance organizations. Separating apples from oranges

Area of Science:

• Health Services Research
• Healthcare Management
• Public Health

Background:

• Health Maintenance Organizations (HMOs) report hospitalization rates, typically measured in bed days per 1,000 enrollees.
• These reported rates often fail to account for out-of-plan utilization, where enrollees receive care outside the HMO's network or coverage.
• Inaccurate utilization data can lead to flawed healthcare planning and resource allocation.

Purpose of the Study:

• To identify and enumerate reasons for unreported inpatient utilization among HMO enrollees.
• To highlight the limitations of current HMO utilization data collection methods.
• To emphasize the need for a more comprehensive approach to measuring total healthcare utilization.

Main Methods:

• Review of existing literature on HMO utilization and reporting practices.
• Survey of utilization data reporting by three selected HMOs.
• Analysis of various scenarios leading to unreported hospital admissions.

Main Results:

• HMOs only track admissions they are aware of and pay for, not the total hospital experience of their enrollees.
• Unreported admissions occur when other insurers (e.g., Medicare, Workers' Compensation) pay, when services are not covered by the HMO, or due to procedural denials.
• Estimated true HMO hospitalization rates could be 7–37% higher than reported figures.

Conclusions:

• Current HMO hospitalization rates are likely underestimates of true utilization.
• A significant portion of inpatient care received by HMO enrollees goes unreported in standard metrics.
• Future research should focus on developing methods to quantify total healthcare utilization across all insurers and providers.