I would like to know if everyone is reading all DAT tests microscopically routinely or only in selected cases.

We do almost all of our DAT testing in gel, but, even in the old days of tube technique, we never read them by tube.

A quote from Peter Issitt (Applied Blood Group Serology, 3rd edition, page 69),

"Now that most saline and albumin tests are carried through to an antiglobulin reading the question of how to read them does not often arise. They are usually read macroscopically in order that the cells and serum are left in the tube for progression of the test. A few cells may, of course, be removed an examined microscopically at any stage if this type of reading is required. However, this author has believed for years that routine use of the microscope in the blood bank creates far more problems than it solves. Almost any cell suspension, including those in which washed cells have never been exposed to antibody, if examined carefully enough under the microscope will be found to contain a few small clumps of red cells. Thus, this author (grudgingly) admits that reading aids such as mirrors or hand lenses are acceptable (for other,s he still reads with the naked eye against a ceiling light source himself) he does not condone routing use of the microscope. This reasoning also applies to the reading of antiglobulin tests. Again, this author believes that if agglutination cannot be seen with the naked eye, a hand lens, a convex mirror or the type of microscope in which the contents of the tube are viewed while still inside the tube by placing the tube itself on the microscope stage, IT IS NOT THERE. Were it not for special tests, such as those in which mixed-field reactions may have occured, when a small percentage of fetal cells might be present in a maternal sample, this author would start a movement to BAN THE MICROSCOPE from the blood bank.

Enzyme tests for agglutination or following conversion to antiglobulin reading, should NEVER be read microscopically."

I agree!

The one role I see for microscopic reading of direct antiglobulin tests is in transfusion reactions if one is looking for a small population of coated cells (i.e. mixed field). Occasionally, it may be useful for trying to get a better feel for a reaction that was questionable macroscopically. Does anyone else see value in these situations?

I see from where you are coming Mabel, but the more sensitive test in such a situation is the elution, even if the DAT is negative, as long as the clinical situation makes you suspect a clinically significant transfusion reaction. If it isn't clinically significant, it is a delayed serological transfusion reaction (on the grounds that an acute reaction is a proper reaction).

No on DATs. Occasionally we will use the scope to check for rouleaux in rough ABO/Rh's or IS crossmatches.

Scott

Mabel,

In case of a positive DAT we do it to see if there is a mixed-field (transfusion).

We grade the all reactions macroscopicly and only read microscopic to look for pseudo-agglutionation or mixed-field reactions.

Peter

Read all DATs microscopically.

We routinely perform DAT in the tube and read microscopically.

The only DATs we routinely checked under the microscope were ones on cord bloods. Not really sure why we continued to scope even those. Probably the "Nobody wants babies to die" mentality. We had stopped routinely checking all DATs about 10 years before I left but I still had older techs who did when they thought I wasn't looking. But then they continued checking the coombs phase of their tube testing under the scope as well. Old habits are hard to break, especially when you are trying to break them from the outside.

I agree with using the 'scope to verify what you're suspecting macroscopically. I like using an agglutination viewing mirror. A reference tech I once worked with said it well...the microscope should be a tool, not a crutch. Unfortunately the current SOP I must follow requires microscopic confirmation of negatives. As an experienced tech, I choose to test in duplicate and use my best judgement whether or not it's necessary.

Microscopic readings are not required for routine antigen typing. Many labs do not read microscopically except in special circumstances, e.g., mixed-field agglutination (MFA) that may not be apparent with the naked eye. Reading is done on 4 - 6 fields using an inverted microscope. It is important to (1) make sure the cell button is totally resuspended prior to reading, otherwise agglutinates may remain in the button, with only free cells being read; (2) examine at least 4 - 6 fields, otherwise weak reactions or MFA may be missed; (3) read cell suspensions that are neither too heavy nor too light, otherwise weak reactions may go undetected.

We read DAT's on cords microscopically.

We don't read DATs on adults microscopically, and we do DATs on newborns in gel, so no micro there either!

We do all DATs in gel and hence do not nedd microscope. In case where we suspect or see (in gel) some mix-field reaction, we do DAT by tube and then check it with microscope. But I agree with Malcolm, in many cases it causes more problems than it solves, with techs arguing....weak?... +/-?... or neg?:confused:

Dear Mabel,

We check all the negative reactions microscopically for verification .

But I want to know why you started this thread because there must be a strong scientific point which you want to make us realize.

I moved into this job a few years ago and have slowly been changing procedures that I felt needed it. I previously had not read all DATs micro but this place has done so for years. I wanted to know what others were doing before I made the change to our procedures. We are planning to get automation in BB in the next year or so and, if we choose gel, the DATs will be more sensitive than tube I think, so it may be more like reading them micro anyway. At least years ago when I first started using gel, I thought they were so much more sensitive that I wasn't sure that I wanted to turn out all those cord blood samples on O moms as DAT pos. Would others agree that gel DATs are more sensitive than tube?

I moved into this job a few years ago and have slowly been changing procedures that I felt needed it. I previously had not read all DATs micro but this place has done so for years. I wanted to know what others were doing before I made the change to our procedures. We are planning to get automation in BB in the next year or so and, if we choose gel, the DATs will be more sensitive than tube I think, so it may be more like reading them micro anyway. At least years ago when I first started using gel, I thought they were so much more sensitive that I wasn't sure that I wanted to turn out all those cord blood samples on O moms as DAT pos. Would others agree that gel DATs are more sensitive than tube?

We studied and compared tube DAT to gel DAT on newborn blood sample many years ago. We did not see any false positives comparing gel to tube. We found gel DAT to be far superior to tube DAT and have never looked back...

Would others agree that gel DATs are more sensitive than tube?

Much, much more so, but not so much so that you get positive results with all patients.

I think I've started my own "so-ing bee" in the last sentence!!!!!!!!!!

:giggle::giggle:

Edited March 26, 201312 yr by Malcolm Needs

We studied and compared tube DAT to gel DAT on newborn blood sample many years ago. We did not see any false positives comparing gel to tube. We found gel DAT to be far superior to tube DAT and have never looked back...

We find just the opposite. Quite a few weak positives in gel that are clean and smooth in the tube. Strange but true.....

I agree with Malcolm,and I will add that Gel Column Agglutination DATs provide also a sensitive means for detecting mixed-field agglutination reactions.

The reactions will look like a band of red cell agglutinates on top of the gel and a pellet of unagglutinated cells at the bottom of the microtube.

This is not a scientific answer, but real world. I have older techs ( 60 yrs+) who are generalists. If I had only macroscopic criteria, we'd never have any positives! We do all DAT's with tube and read all microscopically. I have an Echo and running baby DAT's on it is just too cumbersome even though its probably more sensitive.

Hi Mable,

All DATs are performed with tube testings at my lab and we have to read all reactions microscopically. We do not use gel.

we using gel , and if we found some MF or not a cleared result like a vary weak reaction with our automation shows "?" mark .

then we confirm it with tube method and finalised it with microscopy by running along control or check cell .

We will not read our reaction microscopically, sometimes by tube ,sometimes by gel.

I think gel is more sensitive than tube on neonate DAT.

I think your staff need to have a periodically check ups of vision and color blindness as part of the staff competences.

This is not a scientific answer, but real world. I have older techs ( 60 yrs+) who are generalists. If I had only macroscopic criteria, we'd never have any positives! We do all DAT's with tube and read all microscopically. I have an Echo and running baby DAT's on it is just too cumbersome even though its probably more sensitive.