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New Technique for Immunohistochemical Staining May Decrease Run Time With Only Slightly Diminished Accuracy: Presented at ASCP

By John Otrompke

CHICAGO -- November 3, 2009 -- A new method of performing immunohistochemical staining dramatically improves run time while only slightly decreasing accuracy, according to a study presented here at the American Society for Clinical Pathology (ASCP) 2009 Annual Meeting.

The new method uses wave motion and vacuum technology from Celerus Diagnostics to speed tests, according to Andrew Schubeck, MD, Department of Pathology, Mount Sinai Medical Center, Miami Beach, Florida.

"The slides sit in a little tray that goes through an opening and closing motion, which creates a wave motion of the reagents across the surface of the slide," said Dr. Schubeck on October 29.

In immunohistochemical staining, an antibody is added to tissue, followed by a chromogen agent detector that turns a certain colour whenever the antibody has stuck to the tissue.

"For example, these tests can be used by pathologists for cancer patients if the doctors do not know where the primary tumour is," Dr. Schubeck explained.

The researchers attempted to validate an in vitro method of testing for oestrogen receptors in breast cancers. In the study, 165 previously tested invasive human breast cancers were analysed (34 in whole sections and 131 by tissue microarray, in which samples of 131 different tumours can be tested on 1 slide). The tissues had previously been tested by 2 robotic reagent-dispensing systems.

"Some breast cancers are hormone driven, and doctors can use hormone-therapy drugs such as tamoxifen to treat them," according to Dr. Schubeck.

Tumour sections were pretreated in a pressure cooker (citrate pH 6) before incubation with the primary antibody, followed by a 2-step polymer detection, followed by enzyme chromogenic localisation. Parallel testing on the new technology was done with similar polymer detection.

When examining for oestrogen receptors, the researchers looked at how darkly the slide stained and what percentage of tumour cells were staining. The samples were scored 0, 1+, 2+, or 3+, with 0 being negative and 1+ being a weak positive.

The average turnaround for the new system was 20 minutes, versus 2.5 hours on existing systems. The old and new systems were in 99% agreement for the positive and negative subgroups, according to the researchers.

"In 6 of 135 cases, there was a slight difference in degree. In 2 cases, the slides showed negative on the new platform," Dr. Schubeck said.

[Presentation title: Validation of a Novel Rapid Automation Technology for Immunohistochemical Testing of Estrogen Receptor in Breast Cancer. Abstract 4]

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