February, 2003
© 2000, 2001, 2003 Scott S. Emerson, M.D., Ph.D.
Predictive values when prevalence is low
Ex: Screening for marriage exam
·Prevalence of syphilis 2%
·PV+: 48% with positive VDRL have syphilis
VDRL
Pos Neg |
Tot
Syphilis
Yes 18 2 |
20
No 20
960 | 980
Total 38
962 | 1000