Professor Mark Greene and his colleagues at the University of Pennsylvania School of Medicine report, in the March online issue of Nature Medicine, their development of a high-throughput method that can detect blood proteins at concentrations much lower than current methods, including ELISA (Enzyme-Linked Immunoadsorbent Assay). ELISA is a widely employed technique, which uses enzymes linked to an antibody or antigen as a marker for picking out specific proteins. For example, ELISA is used in a clinical lab to test for exposure to infectious agents such as HIV which it does by detecting antibodies to it present in a blood sample. This new method, called FACTT (Florescent Amplification Catalyzed by T7-polymerase Technique), works on a similar principle but is over 1,000 times more sensitive than ELISA.

The researchers report early studies of the breast cancer marker Her-2/neu that cannot be detected in blood by ELISA until the tumour is fairly big. Testing breast cancer tumour tissue for Her-2/neu is primarily used to select patients for treatment with Herceptin (trastuzumab). The research used blood samples from healthy and breast cancer patients whose tumour tissue did or did not show abnormal amounts of Her-2/neu. Using the new method, patients with Her-2/neu positive breast cancers showed dramatically raised serum Her-2/neu levels with a mean of 384 ng/ml, while those with Her-2/neu negative breast cancers only averaged 19.5 ng/ml which was close to that seen in healthy controls (16.6 ng/ml).

With FACTT, nine out of 10 patients with Her-2/neu positive tumours had raised serum Her2/neu levels and one out of four with Her-2/neu negative tumours had an elevated level. Using ELISA only two out of 10 with Her-2/neu positive tumours had raised serum Her-2/neu levels.

Recent clinical trials support the notion that early treatment can prevent tumour recurrence. Prof Greene believes FACTT technology represents a way to couple early diagnosis with early treatment and therefore improve prognosis.

Note that new tests like this may turn out to be impractical for routine use or when studied more closely may fail to live up to initial results. Thus they may never be used in routine laboratories.