Figure 8. Ambulatory Care Sensitive Admissions per 1,000 Population by ZIP Code Area Income, San Francisco, Ages 40-64, 1999

[D] Scatter diagram of ZIP code areas, with Percent of Households With Incomes Less Than $15,000 on one axis and Admissions per 1,000 Population on the other axis.

ACS rates include conditions where substantial differences of opinion can exist among physicians on whether the patient needs to be admitted or can be treated safely in an outpatient setting. While research has established that differences in ACS rates between low- and high-income areas within a geographic region are not attributable to these practice style differences (Bindman et al., 1995), caution is required in making comparisons of absolute rates among areas, especially those separated by substantial geography. This problem is effectively illustrated by comparing ACS rates for adults age 40-64 in Baltimore (Figure 3) and San Francisco (Figure 8). There is a strong association between ACS rates and ZIP code income in both communities, and there is a fourfold difference between rates for low- and high-income areas in both areas. However, the mean rate in San Francisco (13.17) is about half the rate in Baltimore (26.69), reflecting the generally lower hospital utilization levels on the west coast.

Key: Each square represents a ZIP code area.

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