Evaluation of a simple line width test involving magnetic resonance spectroscopy of plasma in carcinoma of the ovary. Magnetic resonance spectroscopic (MRS) measurement of human plasma has been reported as a generally applicable marker for malignancy: patients with malignancy had a MRS line width significantly different from patients with benign diseases or healthy controls. The authors investigated the value of this test in 213 women with ovarian carcinoma, benign pelvic masses, benign nongynecologic diseases, and healthy controls. The MRS measurements were performed on plasma samples at 21 degrees C or 27 degrees C. The line width parameters were obtained by averaging the width at half the height of the methyl and methylene peaks on the resonance spectra. At 27 degrees C using 33 Hz as the threshold for an abnormal result, there was a significant correlation between the result of the test and the presence or absence of malignancy. However, the study demonstrates that the specificity (0.44) and positive predictive value (0.42) are too low for the test to be useful in the management of patients with carcinoma of the ovary. At 21 degrees C no correlation between the results of the test and the clinical status of women with carcinoma of the ovary were observed. In 47 patients the test did not predict preoperatively the benign or malignant nature of a pelvic mass. 