Monocyte monolayer assay: an efficient noninvasive technique for predicting the severity of hemolytic disease of the newborn.

The authors performed monocyte monolayer assays (MMAs) with the use of normal donor monocytes, and homologous reagent red blood cells, sensitized in vitro, with antibodies in maternal sera. The sera were from 16 pregnant women with Rh antibodies, drawn at the time of amniotic fluid analysis. They compared the predictive value (PV) of the MMAs and the delta OD 450 of amniotic fluid in forecasting the need for transfusing the infant. The PV of the delta OD 450 result in Liley zone mid II-III was 100%, but in zones 0 to low II it was only 60% (13 samples from ten women were in these zones but four babies required transfusion). In contrast, the PV of a positive (greater than 20% reactivity) MMA was 91% (one false positive result) and the PV of a negative MMA was 100%. Thus, the MMA was more efficient than amniotic fluid analysis at predicting hemolytic disease of the newborn severe enough to require transfusion. The noninvasive MMA could be used as a screening test, reducing the number of amniocenteses or ultrasound evaluations performed on Rh-sensitized women.