Regarding the TnI assay on the Axsym.
I did a fairly extensive investigation of the Axsym TnI assay in our lab
recently; looking at false positive results before and after the
reformulation of the assay. The new version of the assay was tested against
a patient with significant heterophile antibody interference (TnI >600n
g/ml) and also against several patients with elevated rheumatoid factor who
also showed significant (>2 ng/ml) levels of TnI with the original
formulation. The new packs returned results <2 ng/ml on all samples
previously demonstrating interference.
However, our greatest source of false positives in this assay has always
been from serum samples where clots have been aspirated. In these cases an
erroneous result (often above 10) can be reported. We now check all
positive TnI samples for clots. We regularly pick up false positive results
with this check and re-assay (after clot removal) to get the "correct"
result. We prefer plasma samples for this assay but often receive serum,
even on patients recieving anti-coagulant therapy.
Regards,
Bill McConnell.
At 07:07 29-11-99 -0500, you wrote:
>Martin Holland wrote: We are about to set up a Troponin assay in this
laboratory. We could have settled on an Abbott kit (we have an AxSym and
Architect) but have decided not to in view of their current supply
difficulties and problems with assays.
>
>Regarding the problems, we had another interfering antibody incident with
TnI this weekend. A sample with positive rheumatoid factor gave about 4
ng/mL TnI on the AxSYM with the reformulated reagent. It had normal total CK
activity and CKMB mass and <0.5 ng/mL for TnI on the Stratus.
>
>
>James J Miller, Ph.D., DABCC
>Associate Professor
>Dept. of Pathology & Laboratory Medicine
>University of Louisville
>Louisville, KY 40292
>
>502-852-1179
>
>
>
-----------------------------------------------------
Bill McConnell
Senior Medical Scientist and acting RPH Webmaster.
Department of Clinical Biochemistry
Royal Perth Hospital.
Perth, Western Australia.
Phone: +61 89 279 8509 (home) +61 0418 922 875 (mobile)
+61 89 224 1176 (work) or +61 89 224 2491 (work fax)
e-mail: [log in to unmask] (home) [log in to unmask] (work)
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