Background: Because of the poor survival outcomes associated with advanced ovarian cancer, early detection strategies are needed. Although several symptom indices have been described, their relationship with the potential lead time has been poorly documented.
Methods: Women aged 50-79 years who had newly diagnosed ovarian cancer (n = 194) and control subjects (n = 268) who attended ovarian cancer screening clinics were included in the analysis. Symptoms and their onset dates were obtained from three sources: a questionnaire (191 case patients and 268 control subjects), telephone interview (111 case patients and 125 control subjects), and general practitioner (GP) notes (171 case patients and 227 control subjects). Data from questionnaires and GP notes were used to derive two new symptom indices (Index 1 and Index 2). Sensitivity and specificity for these new indices and the previously reported Goff index were calculated for the periods of 0-11 and 3-14 months before diagnosis for all three data sources.
Results: For each data source and period, the two new symptom indices derived from questionnaire and GP notes were similar both qualitatively (symptoms included) and quantitatively (sensitivity and specificity) to the Goff index. When symptoms that started within 3 months before diagnosis were excluded, sensitivity was decreased for all indices and all data sources (eg, for telephone interviews, sensitivity for the period 0-11 vs 3-14 months before diagnosis: for Index 1 = 91.0% vs 69.4%, difference = 21.6%, 95% confidence interval [CI] = 13.6% to 29.7%; for Index 2 = 91.0% vs 60.4%, difference = 30.6%, 95% CI = 21.7% to 39.6%; and for the Goff index = 75.7% vs 51.4%, difference = 24.3%, 95% CI = 16.0% to 32.7%). Also, the specificity of all indices was consistently decreased for telephone interviews compared with questionnaires and GP notes (eg, 1 - specificity for the period of 3-14 months before diagnosis for telephone interviews vs questionnaires: for Index 1 = 19.2% vs 10.4%, difference = 8.8%, 95% CI = 1.0% to 16.6%; for Index 2 = 14.4% vs 6.7%, difference = 7.7%, 95% CI = 0.9% to 14.5%; and for the Goff Index = 7.2% vs 1.5%, difference = 5.7%, 95% CI = 0.9% to 10.5%).
Conclusions: Previous estimates of index performance have been overly optimistic because they did not take into account the time required to make a diagnosis on the basis of testing in response to symptoms. In addition, the specificity of a symptom index is lower when based on a telephone interview vs questionnaire or GP notes. Thus, the clinical utility of a symptom index depends on precisely how it is used and how index-positive women are managed.