1037 Reducing the burden of fetal surveillance using the negative predictive value of anti-Ro antibody titer

Abstract

The risk of fetal atrioventricular block (AVB) in anti-Ro exposed pregnancies approximates 2% with no prior affected pregnancies. Antibody titer may be contributory to AVB, but there are no data on the negative predictive value (NPV) of antibody titer identifying fetuses unlikely to develop AVB, thus averting costly serial echocardiographs currently recommended for all anti-Ro pregnancies. Using a commercial core laboratory specifying anti-Ro52 and anti-Ro60 antibodies, we sought to develop a threshold level identifying fetuses unlikely to develop AVB, thus averting costly echo surveillance currently recommend for all anti Ro pregnancies. We performed a retrospective multicenter (Children’s Hospital Colorado fetal database and NYU Research Registry for Neonatal Lupus) review of women screened for anti-Ro antibodies by several local commercial laboratories because of rheumatic disease or a previous child with AVB. Serum from anti-Ro positive women was sent to a 2nd commercial core laboratory at Associated Regional and University Pathologists laboratories (Salt Lake City, UT) to determine anti-Ro52 and anti-Ro60 antibody (TheraDiag, France) levels. We calculated the NPV individually of anti-Ro52 and anti-Ro60 and the two combined (anti-Ro) using a logistic regression model and a parallel testing strategy. Of 332 women, 142 had a child with AVB and 190 never had a child with AVB. An anti-Ro60 threshold of <101 AU/mL achieved 90% NPV for AVB with 79 titers falling below the threshold (Figure). The logistic regression model with both anti-Ro52 and anti-Ro60 using a threshold of a predicted probability <22% achieved a 91% NPV with a larger sample size below the cutoff (n=87) than any other method (Table). While we could not determine a cutoff for no AVB, the likelihood of AVB developing if the maternal anti-Ro60 titer <101 AU/mL is 10%. Our logistic regression model gives a likelihood of 9% to develop fetal AVB below the threshold. These data may help to guide surveillance of future anti-Ro positive pregnancies.View Large Image Figure ViewerDownload Hi-res image Download (PPT)