August 30, 2016 SPADA Meeting Book

“Pre-event” Ex.: Increase PV+ by using > 1 Test

Individual with clinical scenario with fever, followed by centifugal rash: PREV PV+ PV Test 1: - 10.00% 92.80% 99.80% 1% 50% 99.99% 0.10% 9% 100.00% PREV PV+ PV - 50.00% 95.00% 95.00% 10% 67% 99.00% 1.00% 16% 99.50% sensitivity 99%, specificity 99% Test 2: sensitivity 95%, specificity 95% 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