CDC has set guidance to indicate who should be tested for Zika virus infection. IDPH will use the CDC testing criteria to determine suitability for testing.
The IDPH Laboratory is using the CDC Emergency Use Authorized Trioplex assay to detect dengue, chikungunya, and Zika viruses by PCR in serum and cerebrospinal fluid (CSF) samples. The CDC Trioplex rRT-PCR is a real-time reverse transcriptase PCR (rRT-PCR) for the qualitative detection and differentiation of Zika, dengue, and chikungunya viruses from individuals meeting any of several sets of CDC Zika virus clinical criteria: 1) Clinical signs and symptoms associated with Zika virus infection, 2) CDC Zika virus epidemiological criteria (e.g., history of residence in or travel to a geographic region with active Zika transmission at the time of travel, or other epidemiologic criteria for which Zika virus testing may be indicated as part of a public health investigation), and 3) Sexual exposure to a person with a previous positive PCR or serology result for the Zika virus.
The Trioplex rRT-PCR is designed to detect virus (Chickungunya, Dengue, and Zika) in specimens and is therefore best suited to evaluate specimens from individuals collected in the initial period following illness onset. It can be used on serum and cerebrospinal fluids to assay for all three viral types, and in the urine, amniotic fluid, and whole blood to assay for Zika Virus only. These alternate specimen types require teh submission of a patient-matched serum specimen.The Trioplex rRT-PCR test takes a minimum of four hours to complete.
Serological testing is necessary for individuals who submit specimens collected after the initial period following illness onset. Specimens from individuals with a less recent exposure to Zika virus should only be tested using serological methods. The IDPH Laboratory is running the CDC Zika MAC-ELISA test for Zika virus IgM antibodies. Specimens that test positive, equivocal or inconclusive for Zika IgM antibodies will be shipped to CDC for further testing and characterization, due to the possibility of cross reaction between antibodies against other flavivirus species and the Zika virus. The lab is currently is evaluating a serology test for dengue and chikungunya IgM developed by EuroImmun. If these tests are successfully validated, the screening information provided by these tests will be helpful in verifying Zika positive IgM tests within the IDPH Laboratory.
The laboratory will have the capacity to run 50 PCR specimens and 40 serology tests per day. Programmatic authorization is required for specimen testing. Authorization is signified through the use of an authorization number that is written on the submission form.