Table 1.

Zika Test Types and Characteristics

Class of Test	Specific Type of Test	Estimated Sensitivity	Estimated Specificity	Risk of Cross-Reactivity	Timing
Molecular: identify Zika RNA	Polymerase chain reaction; transcription-mediated amplification	Incompletely characterized; tests currently authorized for US use have labeled limits of detection across three orders of magnitude. So, while some are extremely sensitive, the least sensitive tests would have failed to detect more than half of positive cases in a recent, large Nicaraguan cohort.	Incompletely characterized but expected to be high.	Expected to be rare.	Only positive while the person is viremic. Window period is normally short, but will cease positive results within a few weeks after symptoms resolve. Mild and nonspecific symptoms for many patients complicate correct timing.
Serologic: identify antibody against Zika	Enzyme-linked immunosorbent assay	37% to 100% in various studies.	66% to 100% in various studies. Risk of false positives calls for confirmation by plaque reduction neutralization test under certain situations in CDC algorithm.	8% to 40% in various studies, which would reduce effective specificity when cross-reacting viruses are likely present.	Most tests identify IgM, which usually develops within a few days after symptoms and decline after about three months (though it sometimes be detected for over a year). A few tests identify IgG, which develops later, although as early as 10 days after symptoms in some cases, but persists for years.