Prognostic factors for mortality in nasopharyngeal cancer: accounting for time-dependence of relative risks.

BACKGROUND: Few studies have assessed the role of prognostic factors for mortality from nasopharyngeal cancer and even fewer used multivariable methods. Most of these studies relied on the Cox model without testing the proportional hazards assumption. METHODS: A cohort of 76 cases of nasopharyngeal cancer recorded in the Rhône, France, between 1980 and 1985, was followed until 1995. Proportional hazards assumption was tested for each putative prognostic factor. Two multivariable models were built using forward selection of prognostic factors: the Cox model and a flexible model in which variables not meeting the proportional hazards assumption were represented by a time-varying hazard ratio. RESULTS: Only Epstein Barr Virus Nuclear Antigen (EBNA) serology, a marker of infection by the Epstein-Barr virus, and tumoral extent were selected in the analysis based on the Cox model. In contrast, four prognostic factors were significant at alpha = 0.05 level in the flexible model: initial EBNA serology, tumoral histology, age and tumoral extent, the last two not verifying the proportional hazards assumption. The relative risk of age increases with duration of follow-up whereas the effect of tumoral extent changes in a non-monotonic pattern. CONCLUSION: We showed the importance of taking into account the non-proportionality of hazards which can influence results and yield new insights about the role of prognostic factors in nasopharyngeal cancer. Because of the small size of our cohort, our results have to be confirmed in an independent study.

[Quality assessment of the medical information on the standardized discharge summary]. / Evaluation de la qualité de l'information médicale des Résumés de Sortie Standardisés.

BACKGROUND: DRG-based management of public hospitals in France involves the use of standardised discharge abstracts for the "Medicalisation of Information Systems Program". METHODS: To assess the quality of the medical information in these abstracts, a sample of 649 abstracts for 1994 was collected from the Hospices Civils de Lyon's data base. To validate the information in these abstracts, we reviewed the medical records of each patient. RESULTS: The results showed an error rate of 32% (CI: 28-36) for the diagnosis-related group and an error rate of 40% (CI: 36-44) for the principal diagnosis. There was no significant difference between these error rates and the calculation of "Indices Synthétiques d'Activité" (French system for attributing points to hospital stays according to DRGs categories). CONCLUSIONS: The quality of the medical information for the "Medicalisation of Information Systems Program" remains a major challenge not only for budget allocation, but also for the study of the case-mix in hospitals.