SPADA

“Pre-event” Ex.:

Increase PV+ by using > 1 Test

Individual with clinical scenario with fever, followed by

centifugal rash:

PREV PV+

Test 1:

sensitivity 99%,

specificity 99%

10.00% 92.80% 99.80%

1% 50% 99.99%

0.10% 9% 100.00%

PREV PV+

Test 2:

sensitivity 95%,

specificity 95%

50.00% 95.00% 95.00%

10% 67% 99.00%

1.00% 16% 99.50%

Pre-event: Prevalence of Smallpox is Zero

Peri-event: Prevalence of Smallpox is Low

• Clinical scenario should be consistent

– Use febrile rash algorithm; validate algorithm

• Wide availability of other key diagnostic tests

especially rapid VZV testing to rule in VZV

• Limit the number of laboratories performing

Variola

virus

testing

– Establish confirmatory testing protocols

• Approaches to improving predictive value positive:

implications for result use (rule in, and institution of

vaccination campaign vs. rule out)

– Use more than 1 test (different targets)

– Use tests without common sources of false positives