Challenges of Zika Virus Testing in Pregnancy in the Setting of Local Mosquito-Borne Transmission

Abstract

Background. Zika Virus (ZIKV) infection in pregnancy is a major clinical concern. The CDC recommended that pregnant women living in an area with a ZIKV travel notice undergo ZIKV screening in the first and second trimesters of pregnancy. This study investigated the consequences of this screening on clinical management. Methods. An IRB approved retrospective chart review was conducted using laboratory records of ZIKV testing on pregnant patients from January through December 2016 at multiple tertiary care centers in Miami, FL. Serum and/or urine samples were collected, based on CDC guidelines at the time, and evaluated for PCR and/or IgM evidence of ZIKV infection. Positive ZIKV PCR results indicated acute phase of infection. Previous infection was suggested by positive IgM antibody, but required confirmatory ZIKV plaque reduction neutralization testing (PRNT) testing due to IgM antibody cross reactivity with other flaviviruses. Results. During 2016, 2,327 pregnant women were screened for ZIKV infection. At the peak in August 2016, 607 (26%) patients were tested and only 31 (5.1%) tests resulted within the month. Of those screened, 113 (4.85%) women tested positive for ZIKV PCR and/or IgM. In October 2016, 40 (35.4%) positive screening tests were received, the most positives resulting in a month. Confirmatory ZIKV PRNT testing was performed on those who were ZIKV IgM positive and PCR negative, with a total of 92 results received. Eighty-eight women were considered positive, 49 confirmed with positive titers (≥10). There were 28 women with negative titers (< 10), thus a false positive ZIKV screening rate of 30.4%, and 15 results were pending. Of women with false positive IgM screening, a median of 1 (range 0-4) additional ultrasound was done between receipt of the initial positive ZIKV screening and the subsequent receipt of the negative PRNT testing. Delays of results led to 21 (24%) positive tests reported after delivery and hospital discharge. Additionally, 18 (20.5%) women who tested PRNT positive had their originating sample drawn during admission for delivery with results available only after discharge. Conclusion. Both delays in ZIKV testing results and false positive screening with ZIKV IgM led to challenges in counseling and clinical care of pregnant women living in an area of ongoing ZIKV transmission.