dcubed Posted August 9, 2017 Share Posted August 9, 2017 I need help understanding a strange phenomenon. I have a D negative Mom by gel testing that has delivered a D positive (3+) infant by gel testing. A maternal post delivery sample was used for an FMH screen. The FMH screen was macroscopically positive 1+w. The Mom's post delivery sample was tested for weak D and was found to be 1+w. The Mom's pre delivery specimen was tested for weak D and it was negative. The sample was tested for FMH with a KB stain an no fetal cells were seen. I was expecting the KB stain to reveal a large number of fetal cells. LIMPER55 1 Link to comment Share on other sites More sharing options...
R1R2 Posted August 9, 2017 Share Posted August 9, 2017 What were the blood types of mom and baby? Link to comment Share on other sites More sharing options...
dcubed Posted August 10, 2017 Author Share Posted August 10, 2017 What were the blood types of mom and baby? Mom is O Neg and baby is O Pos. Link to comment Share on other sites More sharing options...
jalomahe Posted August 10, 2017 Share Posted August 10, 2017 First, you have a discrepancy between the Mom's Rh type on the pre- vs. post-delivery specimen. That needs to be resolved just as you would need to resolve an ABO discrepancy. I would suggest that a new specimen be collected from the Mom and tested. If the new specimen's Rh type agrees with the pre- specimen, then it would indicate there was a problem with your post specimen either misidentification or contamination. Repeat the rosette test on the newly collected post specimen. If the new specimen's Rh type agrees with the original post- specimen then you have your answer that the rosette test is false positive due to the Mom having a weak expression of D which interferes with rosette testing. You are not detecting Rh + fetal cells, instead you are detecting Rh + (weak) maternal cells which would explain why the rosette test is positive but the KB stain is negative. You would also then need to follow up as to the pre- sample and whether it was misidentified at collection, etc. Yanxia, Malcolm Needs, TreeMoss and 2 others 5 Link to comment Share on other sites More sharing options...
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