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Figure 2. Proton COSY spectrum of a colon tumor. The cross peaks of interest are labeled Y and Y'. Assignment of the other labeled peaks has been described earlier (11).
mor. The ID resonances lie along the diagonal of the COSY spectrum, whereas off-diagonal cross peaks demonstrate which groups of chemical shifts are spin-coupled to one another. A good example is given by cross peaks Y and Y', which result from coupling between a -CH3 and a >CH(OH) moiety. Possible candidates for cross peaks in this region are lactic acid, the amino acid threonine, and the sugar fucose. Careful consideration of the various parameters described above is essential for the proper design of a medical NMR experiment. This provides an excellent opportunity to enhance the interaction between scientists and medical practitioners. The Fossel test The recent controversy in the NMR community over the Fossel test, a proposed blood test for cancer (3), exemplifies the need for collaboration between clinicians and spectroscopists. The test compares the average of the widths at half-height of the resonance envelopes at 1.3 and 0.8 ppm in the water-suppressed NMR spectrum of plasma. The test is fraught with difficulties because a great diversity of chemical shifts, linewidths, and T2 val-
ues complicates the spectra, making interpretation difficult. Problems arose when the test was subjected to large general populations. The NMR spectroscopy linewidths were found to be very sensitive to the distribution of plasma lipoproteins and triglycerides. Changes in these levels may result for a variety of reasons: diet, trauma, and diseases other than cancer. Many clinical assessments of this test have been reported, and most of these show that the test is not useful for screening an asymptomatic population for cancer (4-10). Although the Fossel test did not fulfill its original expectations, it stimulated a great deal of research on the NMR spectroscopy of plasma and increased awareness of the literature on plasma lipoprotein profiles and their relation to disease. In addition, the test prompted many collaborations among researchers from the basic and clinical sciences. Furthermore, this simple method might be useful for monitoring the response of cancer patients to therapy (4). Malignancy-associated lipoprotein Mountford and co-workers have taken a very detailed approach to NMR anal-
•BROMOICHLORO DIOXINS & FURANS •POLYCHLORINATED MPHENYLS •PRIORITY POLLUTANTS
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ANALYTICAL CHEMISTRY, VOL. 62, NO. 15, AUGUST 1, 1990 . 855 A
