The analysis of delays in disease reporting: methods and results for the acquired immunodeficiency syndrome

In order to monitor accurately trends in disease incidence, it is necessary to account for delays in the reporting of cases to central registries. The objective of the paper is to develop simple methods for the analysis of reporting delays in order to identify the main sources of heterogeneity and to adjust reported disease incidence data. The analysis is complicated because the data are right truncated. A simple and flexible method for the regression analysis of reporting delays is proposed, which can be easily implemented with standard computing tools for generalized linear models or logistic regression. The method was used to analyze delays in reporting the acquired immunodeficiency syndrome in the United States among cases who met the pre-1987 surveillance definition. This analysis showed significant geographic variation. Delays were shortest in the Northeast and longest in the South. The influences of risk groups and calendar year of diagnosis were not consistent across each of the geographic regions. Variation among risk groups was attributed primarily to slower reporting of transfusion-associated and pediatric acquired immunodeficiency syndrome cases. An overall trend toward longer delays with calendar time of diagnosis was attributed primarily to a trend toward longer delays in the Northeast. These methods and results are useful both for the evaluation of surveillance procedures in order to improve disease reporting and for adjustment of disease incidence data.