Weak D

[butlermom]

I would like to get your thoughts. Mother is O neg and baby has a positive DAT. Baby is group A but did not react with anti-D at immediate spin. I have always reported these as "unable to determine Rh due to positive DAT" and given the Mother RhoGam. One of my younger techs on evening shift performed the weak D testing and called it negative. What I discovered was that she only read the Coombs phase MACROscopically. When I repeated the weak D and ran the Gamma-clone control, both were positive under the scope. Obviously the positive control makes the test invalid. We gave the Mother RhoGam. Am I out-dated to still be reading these microscopically? How do you handle these?

[David Saikin]

I try to use a mild heat elution to remove bound ab - this works pretty well for DAT+ of 2+ or less. If you have a microscopic +DAT it would resolve your issue. Microscopic reading is usually frowned upon these days, but sometimes you have to do it. Depends on your staff competence and confidence.

[ANORRIS]

What do you use for you negative control on a weak D?

[JOANBALONE]

What does your weak D procedure say? We do not read weak D under the microscope per procedure.

JB

[David Saikin]

I use 6-8% albumin for Rh control.

What do you use for you negative control on a weak D?

[L106]

Same as JOANBALONE, here. We do not read the Weak D or Weak D Control under the microscope, per manufacturer's package insert instructions.

[butlermom]

I've always interpreted the phrase "...may use an optical aid" in the manufacturer's package insert to mean the microscope. I'm now beginning to think it only means the magnifying agglutination viewer and I should quit reading everything under the scope (except fetal bleed screens and DAT's of course).

[Malcolm Needs ☆]

Well, Peter Issitt always said that the microscope should be banned from transfusion (except for the KBT) and he was no mean serologist!