Laboratory Testing

IMPORTANT NOTICE: Updated Zika Testing Guidance

On April 2, 2018, DSHS updated its testing guidance for pregnant women in Texas.

  • Pregnant women who live in Cameron, Hidalgo, Kinney, Maverick, Starr, Val Verde, Webb, Willacy, and Zapata counties should be tested three times during pregnancy using PCR only.
  • Elsewhere in the state, pregnant women with no symptoms but recent possible exposure (for example, women who have traveled to areas with ongoing Zika transmission) should be tested as soon as possible, up to 12 weeks after exposure, using PCR only.

The guidance for testing non-pregnant residents remains the same.

  • Residents of the nine higher-risk counties with a rash, plus one other common Zika symptom (fever, joint pain or conjunctivitis), should be tested.
  • Residents of any part of the state with three or more Zika symptoms should be tested.
  • Any non-pregnant resident with Zika symptoms starting within two weeks of travel to an area with ongoing Zika transmission or sexual contact with a traveler should be tested.

Read the DSHS Health Alert for more information. Visit the Health Professionals page for information about caring for pregnant women and patients exposed to Zika.

Laboratory testing for Zika virus infection is available at the U.S. Centers for Disease Control and Prevention (CDC). The DSHS Austin Laboratory is performing reverse transcriptase polymerase chain reaction (RT-PCR) for Zika. Please review the Chikungunya, Dengue, and Zika PCR and Serology Specimen Criteria guidance document (75 kb, PDF) (updated Dec. 16, 2016) to facilitate laboratory testing of individuals meeting the testing criteria. Specimens submitted to the DSHS Austin Laboratory must be accompanied by a completed Chikungunya, Dengue, and Zika Testing Supplemental Information Form (65 kb, PDF) (updated Sept. 12, 2016).

On May 31, 2017 the CDC released interim guidance on Zika virus antibody testing and interpretation of results. Because of the differences in recommended clinical management of Zika and dengue virus infections, and the risk of adverse pregnancy outcomes in women infected with Zika virus during pregnancy, a conservative approach to the interpretation of antibody test results is necessary to reduce the possibility of a missed diagnosis of either infection. The timing of IgM antibody testing and the thresholds of plaque reduction neutralization test (PRNT) have changed.

  • Serum IgM antibody test should be performed if real-time reverse transcription polymerase chain reaction (rRT-PCR) results are negative, regardless of the day the specimen was collected.
  • Based on earlier flavivirus research and limited preliminary data specific to Zika virus, the historical use of a 4-fold higher titer by PRNT might not discriminate between anti-Zika virus antibodies and cross-reacting antibodies in all persons who have been previously infected with, or vaccinated against, a related flavivirus (i.e., secondary flavivirus infection).
  • Together with a positive or equivocal IgM to Zika or dengue virus:
    • A PRNT titer >10 will be interpreted as a evidence of infection with that specific flavivirus infection when the PRNT to the other flavivirus(es) tested is <10.
    • A PRNT titer <10 to a specific flavivirus will be interpreted as no evidence of infection with that virus.
    • If PRNTs are positive i.e., >10 to multiple flaviviruses, this will be interpreted as evidence of recent infection with a flavivirus.

CDC will continue to update this guidance as these data are preliminary and as additional rRT-PCR data becomes available. For more information about this guidance, visit Interim Guidance for Interpretation of Zika Virus Antibody Test Results .

Additional guidelines for healthcare providers are on the Health Professionals page.

See a comprehensive listing of contact information by county for local and regional health departments in Texas .

last updated June 13, 2018