TABLE 7.6 Tacoma Studies

Study

Design

Results

Alternative Explanation

HIV seroprevalencea

• CDC non-link 5-year survey protocol;

• Injection drug user entering methadone treatment;

N = 1,109;

• To 1992

2 to 4 percent over 5 years' time

• Low HIV prevalence and incidence imply no presence of transmission risk; needle exchange program does not matter;

• Other HIV interventions

Hepatitis surveillance

case reportinga

• CDC sentinel pre-post needle exchange program;

• To 1990

1985—HBV injection drug user = 40 Sex = 9 Unknown = 13 1990—HBV injection drug user = 7 Sex = 12 Unknown = 6

• Due to normal fluctuation in incidence; saturation in injection drug user community (exhaustion of susceptibles);

• Local health department implemented other prevention interventions

Hepatitis B and C case controlb

Case from injection drug user CDC sentinel surveillance 28 injection drug user—HBV 20 injection drug user—HCV; Control from injection drug user from

• HIV testing and counseling

• Treatment; 38 injection drug user no serologic markers HBV; 26 injection drug user no serologic markers HCV

HBV • Case—75 percent never used needle exchange program;

• Control—26 percent never used needle exchange program;

• OR = 8.4; HCV

• Case = 75 percent never used needle exchange program;

• Control = 26 percent never used needle exchange program;

• OR = 8.1

• Case control not equivalent groups;

• Controls are a bias sample;

• Self-selection bias in use of needle exchange program



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