Date Published: February 22, 2019
Publisher: Public Library of Science
Author(s): Benjamin Blümel, Michaela Diercke, Daniel Sagebiel, Andreas Gilsdorf, Oliver Gruebner.
The German Infection Protection Act requires notifying certain cases of infectious diseases to local health departments (LHD) in Germany. LHDs transmit notifications meeting case definitions to the national health authority, where the proportion of discarded notifications is not known. The proportion of discarded cases at the level of LHDs can be expressed as the positive predictive value (PPV) of the notification system. The PPV can be used to assess the efficiency of the system. We quantified the proportion of discarded notifications to calculate the PPV of the German notification system at the level of LHDs using electronic notification data from Berlin LHDs from 2012. We also analysed reasons for discarding notifications by reviewing notification forms. Data was available from eight LHDs (67%) receiving 10,113 notifications in 2012. Overall PPV was 89% (minimum-maximum = 77–97% across LHDs) and ranging from 30% (Hepatitis B) to 99% (Rotavirus). Of 166 individual investigation forms 84% were on hepatitis B or C cases, most of them discarded because of previously diagnosed chronic disease. LHDs investigate many notifications that do not lead to public health action and useful surveillance data leading to inefficient use of resources. Adaptation of case definitions or the legal framework concerning notifications may increase the efficiency of the notification system and lead to better use of data from notified cases.
Regular evaluation of a surveillance system ensures its efficiency and effectiveness . National and international guidelines for the evaluation of surveillance systems recommend the use of surveillance system attributes such as simplicity, flexibility, data quality, acceptability, sensitivity, positive predictive value (PPV), representativeness, timeliness, and stability to identify gaps and to further develop and improve the system [2–7].
LHDs discard many notifications, of which a large number require investigation by the LHD. Differences in the nature and notification requirements of diseases under surveillance may explain the range of PPVs. The low PPV and the high case numbers of hepatitis B and C suggest that a relevant amount of LHD resources are used to investigate notifications that do not lead to public health action and useful surveillance data. On the other hand, our results also suggest that many hepatitis B cases considered relevant for disease burden may have already been notified to LHDs, although not required by the notification law, and thus can be used for estimation of disease incidence and epidemiological analyses. In 2015 an update of the German case and reference definitions has been published that requires that hepatitis B cases without symptoms of acute hepatitis are included in the calculation of diseases incidences (they meet the reference definition) . Additionally, in 2017 the notification requirements were changed so that laboratories have to notify every case of hepatitis B or C they detect regardless of clinical symptoms and course of disease (acute or chronic). These cases are then transmitted further and included in disease incidence calculations. These changes are expected to increase the PPV for hepatitis B and C.