February, 2003
© 2000, 2001, 2003 Scott S. Emerson, M.D., Ph.D.
Diagnostic Testing: 8
Diagnostic Testing: Example
Predictive values when prevalence is high
Ex: STD clinic
·Prevalence of syphilis 30%
·PV+: 95% with positive VDRL have syphilis
                       VDRL
             Pos   Neg |  Tot
Syphilis Yes 270    30 |  300
          No 14   686 |  700
Total        284   716 | 1000