199 Summary and general discussion 9 All three surveillance indicators have specific advantages and disadvantages. Out of the three surveillance indicators, RT-PCR tests and contact and droplet precautions are most likely to reflect a clinical suspicion of a SARI diagnosis, while ICD-10 diagnostic codes are mostly used in patients with a confirmed diagnosis, which may lead to an underestimation of the number of SARI cases. Moreover, there is often a delay in the registration of ICD-10 codes. RT-PCR tests may be less reliable because the number of tests can be heavily influenced by changing protocols, as happened during the COVID-19 pandemic. A potential downside of using contact and droplet precautions as a surveillance indicator is that they are also indicated in infections unrelated to SARI, although these numbers are very small, especially when compared to SARI. An advantage of contact and droplet precautions is that out of the three, they best reflect pressure on hospital capacity. Moreover, in some patients an PCR test may be considered too invasive, but contact and droplet precautions will still be in place. Even though we lose some precision with the all three surveillance indicators compared to individually screening and selecting patients, there are large advantages when it comes to feasibility. Data collection can be done automatically using routinely collected data, with no additional administrative burden for health care staff. The continuous validation of proxy indicators is essential. This study demonstrated that there are suitable proxies for SARI surveillance. In Chapter 3, the use of anonymous, routinely collected laboratory data could be used for outbreak surveillance. In March 2022, a series of cases of severe hepatitis in young children was recognised in central Scotland. In the majority of outbreaks of infectious diseases, the number of mild cases is much higher than the number of severe cases5. In the outbreak of severe hepatitis in young children, no milder or self-limiting cases were reported. However, it is possible that the outbreak has been more widespread, and understanding the magnitude of the outbreak is essential for the understanding of the disease and identification of milder cases. Hepatitis is characterised by an increase in aspartate transaminase (AST) and alanine transaminase (ALT) levels, for which quantitative recordings are available in clinical laboratory databases. These summary data are rarely used for public health surveillance, but could be used as an opportunistic measure for syndromic disease surveillance. Summary statistics for AST and ALT measurements were collected from 29 hospital clinical chemistry laboratory databases from the United Kingdom (including data from England, Scotland and Wales), the Netherlands and Ireland, over a 10-year period across all age groups. The rate of elevated AST and/or ALT tests for 3-week to 5-year-olds was compared between a period of interest in which cases of hepatitis were reported and a pre-pandemic baseline period, using Z-scores. Combining data for all contributing hospitals, the rate of elevated AST or ALT measurements in the period of interest was not elevated (Z-score -0.46; p 0.64). There were differences in the results from individual regions, with a higher rate of elevated AST or ALT values in the Netherlands (Z-score 4.48; p<0.0001). This study demonstrated that the outbreak of hepatitis in young children was most likely relatively limited. Moreover, federated analytics using aggregated and non-disclosive data was successful, safe and
RkJQdWJsaXNoZXIy MTk4NDMw