DAT - test and albumin control are positive

[ckcheng]

Since the albumin control is to detect autoaggluination, and prolong warm saline wash will elute bound proteins out - what will you do if both DAT test (monospecific or polyspecific AHG) and albumin control are positive? (say in Cold Agglutinin Disease or ......)

(1) Invalid the test since albumin control is positive.

(2) Repeat test after 3X warm saline wash. Report if control becomes negative. Invalid the test if albumin control still positive.

(3) Prolong warm saline wash till albumin control becomes negative.

Thank you very much.

CK Cheng, MSc, SBB(ASCP), CQA(ASQ)

Hong Kong

Nov 11, 2008

[David Saikin]

Why do you have autoagglutination? Either a strongly IgG+DAT or a strong cold aggl. I do not have an answer for you. I guess all your typings would be invalid also, if you had spontaneous agglutination as you describe.

[Yanxia]

I will do elution test, and at the same time have another cells with the appropriate antigen we want to test to be a control.

[ckcheng]

The case was the patient had a very strong auto-anti-I with titer over 8,192. Forward & reverse grouping as well as Rh typing were all positive. When perform DAT, both test and control were positive even after 3X warm saline wash. The question is should we invalid the test or wash with warm saline till control is negative?

CK Cheng, MSc, SBB(ASCP), CQA(ASQ)

Nov 13, 2008

[David Saikin]

Will warm saline washes remove the bound anti-I? If this is cold aggl disease . . . I am not certain. Is the patient hemolyzing? I really don't know what to tell you

[Yanxia]

I am sorry for my misunderstanding in the first post.

I agree with David Saikin. And I think maybe Ckcheng can use microscope to distinguish the real agglutination and mass caused by protein. If I am right this can tell us the DAT IgM result. As for the IgG you can use 2-Me to treat the cells to destroy IgM antibodies.

[RR1]

Hi ckcheng,

Did you resolve this problem ? If so -it would be great to share the outcome on this forum.

Regardless of the albumin control result- what were the monospecific DAT results obtained? and was this by Tube or Gel?

The monospecific DAT gel cards generally incorporate a negative control well - which is just reagent diluent. I don't quite understand the significance of the albumin control you are using.

[ckcheng]

Hi Rashmi, the problem still remains un-resolved. The test was performed using tube test. The purpose of incorporate a negative control (6% albumin) is to test for auto-agglutination. Auto-anti-I was so potent that auto-agglutination observed even AHG reagents were not added, so the positive in AHG reagents became meaningless. Negative in negative control sure can be achieved after reeeepeeeeat washing with warm saline, but does it meaningful?? After a second thought, I tend to invalid the test because negative control remains positive after 3X washing. What do you think?

CK Cheng, MSc, SBB(ASCP), CQA(ASQ)

Hong Kong

May 8, 2009