Comparison of electron paramagnetic resonance and atomic absorption serum copper measurements in human normal control and cancer patients

Serum copper levels of 132 controls and 122 cancer patients (including Hodgkin's disease, lung cancer, breast cancer, leukemia, untreated patients, and patients in progression) were measured using both atomic absorption (AA) and electron paramagnetic resonance (EPR) techniques. The data pairs were compared using linear regression analysis, EPR versus AA, and all the data (controls and cancers) fit a single regression line with a squared correlation coefficient (r2) of 0.80. Comparison of the subpopulations revealed possible small differences, but none great enough to be of diagnostic value for individual patients. Thus, in a number of cases of practical interest, EPR-determined serum copper levels were essentially redundant with respect to AA measurements. Previous reports recommending the use and possible superiority of EPR for serum copper determinations appear not to have compared the EPR and AA techniques adequately or correctly. EPR serum copper measurements may yet provide unique data in these diseases, but a more detailed analysis of the spectral parameters will be required. EPR-determined serum transferrin levels are also reported.