Department of Chemical Pathology, Princess Alexandra Hospital, Woolloongabba, Qld, 4102, Australia
Address correspondence to: Greg Ward, Department of Chemical Pathology, Princess Alexandra Hospital, Woolloongabba, Qld 4102, Australia. E-mail: greg_ward{at}health.qld.gov.au. Current address for P.E.H.: ACT Pathology, The Canberra Hospital, P.O. Box 11, Woden, ACT 2606, Australia.
To the editor:
In the July issue of JCEM, Preissner et al. (1) looked at the prevalence of heterophile antibody interference in the Beckman-Coulter Access/Access 2 thyroglobulin assay and found approximately 2.9% of samples were prone to heterophile antibody interference.
A key point in their discussion referred to some work of ours (2). They stated that we reported a heterophile antibody interference of less than 0.03%. This is, in fact, incorrect. Using the Chiron (now Bayer) Centaur TSH assay, we reported significant heterophile antibody interference in 3.4% of assays that were run without blocking agents added. We found that when using the manufacturers routine assay material, which contained added blocking serum, the presence of heterophile interference dropped to zero. We then stated that in this particular assay, the amount of blocking agent added appeared to be sufficient to eliminate most cases of heterophile antibody interference and only patient samples with massive quantities of heterophile antibodies would be a problem with this assay, and in our experience, this would be approximately 0.03% of the samples we assayed.
The similarity of reported heterophile antibody interference in the paper of Preissner et al. (1) and our finding for the unblocked TSH assay is very close. The implication is that the Beckman assay does not contain added blocking material. We think it likely that most manufacturers are adding blocking agents and that for most assays only occasional samples will be affected. However, this paper graphically demonstrates that one should be very careful in making assumptions about manufacturers and the formulation of their assays!
Received September 15, 2003.
References
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