OVX1 Radioimmunoassay Results Are Dependent on the Method of Sample Collection and Storage

OVX1 is a tumor marker that may be of value in the management of ovarian cancer and appears to be complementary to CA125 measurement (1)(2)(3). The results of a study by Woolas et al. (2) suggested that OVX1 is increased in the serum of a major proportion of patients with stage I ovarian cancer who have serum CA125 concentrations within the health-related reference interval. We, therefore, had planned to include OVX1 measurement in a prospective study of screening for ovarian cancer. Because the screening study involved sending blood samples by post to a central laboratory, we undertook this preliminary study to assess the stability of OVX1 in the 2- to 3-day time period required for postal delivery. All subjects in this study were apparently healthy premenopausal women. Venipuncture was performed on 20 subjects in the UK and 9 subjects in Denmark. The collection tubes, the storage temperature before centrifugation, and the length of storage before centrifugation were varied. All samples were then centrifuged at 2000g for 10 min, and the plasma or serum samples were stored at −20 °C until OVX1 analysis was performed. In addition, to investigate the effect of repetitive thawing and freezing, serum samples from nine subjects were divided into eight aliquots and frozen. After 24 h, seven aliquots from each subject were thawed at room temperature and refrozen after 1 h. This process was repeated daily, leaving one aliquot frozen each day, until the last aliquot was frozen and thawed after 8 day for OVX1 analysis.