Racial differences in encounter rates for otitis media.

In 1975-1976, an experiment was performed at three sites of an HMO to investigate the effect of a protocol on drug prescribing for otitis media. A large and unexpected difference in encounter rates for otitis media was found among the sites. In the first 6 months of 1975, the rate of children less than 15 years with at least one encounter for otitis media at site EI was 155 per 1000 children, compared to 15 per 1000 at site EII. During the study period, most of the patients at site EII were black. The purpose of this paper is to alert readers to factors that affect the rates of disease in clinical practice, to encourage others to suggest reasons for the difference, and to encourage research. Several explanations were investigated to explain the differences: (1) miscoding; (2) age differences; (3) payment status; (4) diagnostic style; (5) differences in encounters per episode; and (6) social differences. Encounters of purulent otitis media were probably not systematically miscoded. The age distribution within the sites was almost identical. The difference in the encounter rates was even greater for children less than 15 years when only the enrolled population was examined. National incidence rates of otitis media showed rates for all ages for whites were 4.1% and for blacks 2.5%. The average number of encounters per episode was 1.4 at all of the study sites. Enrolled children at site EI had higher encounter rates for all reasons than children at site EII. Differences in diagnostic style may account for part of the difference in otitis media between the sites. Differences in encounter rates may also be due to real differences in disease occurrence between blacks and whites, differences in the perception of ear infection, and differences in the tendency to visit a physician for ear problems.