Positive predictive value of the German notification system for infectious diseases: Surveillance data from eight local health departments, Berlin, 2012.

Benjamin Blümel,Daniel Sagebiel,Michaela Diercke,Andreas Gilsdorf,Oliver Gruebner

doi:10.1371/journal.pone.0212908

Benjamin Blümel, Daniel Sagebiel + Show 3 more

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https://doi.org/10.1371/journal.pone.0212908

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Abstract

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.

Highlights

Regular evaluation of a surveillance system ensures its efficiency and effectiveness [1]
We provided all local health departments (LHD) in Berlin (n = 12) with detailed instructions explaining how to extract data stratified by disease, the number of notifications received at the LHD for all diseases that are notifiable to LHDs according to IfSG
In 8 LHDs, 10,113 notifications were recorded in 2012. 8,989 notifications were transmitted resulting in an overall PPVCD of 89%. 8,406 cases met the reference definition resulting in an overall PPVRD of 83% (Fig 3)

Summary

Introduction

Regular evaluation of a surveillance system ensures its efficiency and effectiveness [1]. 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 [2,3,4,5,6,7]. Since 2001 many studies evaluated attributes of the German surveillance system including simplicity, acceptability, data quality, PPV, and timeliness. The studies examined system attributes at different levels of the surveillance system (local, regional, and national) either in a disease-specific or a more general, system-wide way [8,9,10,11,12,13]. One study examined the PPV of the German notification system from the viewpoint of the regional and national levels not including data from the local level [11]

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