Plaque Reduction Neutralization Test (PRNT) in the Congenital Zika Syndrome: Positivity and Associations with Laboratory, Clinical, and Imaging Characteristics

The short duration of viremia, low blood viral load, inaccessibility to timely specific diagnostic tests, and cross-reactions with other flaviviruses have hindered laboratory confirmation of Congenital Zika Syndrome (CZS). This study analyzes the positivity of the plaque reduction neutralization test (PRNT) in children with clinical or imaging characteristics of CZS and its association with laboratory, clinical, and imaging characteristics. The 94 clinical cases of CZS submitted to the ZIKV PRNT(90) test were followed from 2016 to 2018. The mean age of children at PRNT(90) collection was 22 ± 6 months Standard Deviation. The ZIKV PRNT(90) was positive (titer ≥ 10) in 40 (42.5%) children. ZIKV PRNT(90) positivity was associated with severe microcephaly in newborns (p = 0.016), lower head circumference z-score at birth (p = 0.043) and 24 months of age (p = 0.031), and severe reduction of the cerebral parenchyma volume (p = 0.021), expressing greater disease severity. Negative PRNT(90) in children with characteristic signs of CZS may be due to false-negative results, indicating that the diagnosis of CZS should be primarily syndromic.