Which laboratory tests are most useful for confirming Zika virus infection in symptomatic patients?

The most useful laboratory tests for confirming Zika virus infection in symptomatic patients are molecular detection by reverse transcription polymerase chain reaction (RT-PCR) and serological testing for Zika virus-specific IgM antibodies. RT-PCR performed on serum or urine samples within the first week of symptom onset is the preferred diagnostic method due to its high specificity and ability to detect viral RNA during the acute phase of infection NICE CKS. If RT-PCR is negative or the patient presents later than 7 days after symptom onset, serological testing for Zika virus-specific IgM antibodies can be used to support diagnosis, although cross-reactivity with other flaviviruses such as dengue virus may complicate interpretation Sharp et al. 2019. Confirmatory testing with plaque reduction neutralization tests (PRNT) may be necessary to distinguish Zika virus infection from related flavivirus infections in endemic areas NICE CKS.

In summary, RT-PCR is the frontline test for symptomatic patients early in illness, followed by IgM serology and confirmatory neutralization assays if needed.