I am intrigued by the comments regarding pregnancy serum, as we found
elevated troponin I using Beckman Access in some pregnant females, and
considered it to be a true elevation, as for patients on whom we had further
samples, it cleared at a rate which seemed usual for troponin I. In the case
of false positives reported by Steve Binder, is it also some pregnant sera
only, and if so what could be specific to some only ( it did not appear to
relate to stage of pregnancy in our patients)
Helen Grimes, Dept of Clin Biochem, UCHG
-----Original Message-----
From: [log in to unmask]
[mailto:[log in to unmask]]
Sent: Monday, January 08, 2001 9:45 PM
To: [log in to unmask]
Subject: Re: False positive IgM in pregnancy
Dear Dr. Forcina,
I believe that this problem is a general phenomenon
involving pregnancy and is
not specific to Toxoplasma, CMV, or Rubella. The problem is
also encountered in
HIV antibody screening by immunoassay and Western Blot , for
example. We have
hypothesized that the introduction of fetal cells leads to
production of a wide
range of "non-specific" antibodies, especially in early
pregnancy. The
differences which you observe between methods may be due to
the use of a
different blocking strategy.
I am not aware of any discussion of this phenomenon in the
literature, and I
would pleased if anyone could supply citations. It would
also be useful to know
if this occurs most commonly in capture assays (as your
examples suggest), or
whether it is observed in indirect assays as well.
Sincerely,
Steve Binder
Bio-Rad Laboratories, Diagnostic Group
____________________Reply Separator____________________
Subject: False positive IgM in pregnancy
Author: Bruno Forcina <[log in to unmask]>
Date: 1/6/2001 7:55 AM
It is not infrequent to find false positives for IgM
anti-Toxoplasma anti-
CMV an sometimes anti-Rubella in sera from pregnant women.
This we have
noticed with different automated immunoassays such Abbott
Axsym ,Roche
Cobas Core II and Bio-merieux Vidas, sometimes with
conflicting results
for the same sample on different analyzers. Obviously RF has
been ruled out
as a source of interference.
My questions are:
Has this been observed by others?
Should a different cutoff be used for pregnant women?
Any idea for the possible cause of interference?
Bst regards an a happy New Year to everybody,
Bruno Forcina
Laboratorio Forcina
Piazza stazione 78 Galatina Italy
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