App-based COVID-19 syndromic surveillance and prediction of hospital admissions in COVID Symptom Study Sweden

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Abstract

The app-based COVID Symptom Study was launched in Sweden in April 2020 to contribute to real-time COVID-19 surveillance. We enrolled 143,531 study participants (≥18 years) who contributed 10.6 million daily symptom reports between April 29, 2020 and February 10, 2021. Here, we include data from 19,161 self-reported PCR tests to create a symptom-based model to estimate the individual probability of symptomatic COVID-19, with an AUC of 0.78 (95% CI 0.74–0.83) in an external dataset. These individual probabilities are employed to estimate daily regional COVID-19 prevalence, which are in turn used together with current hospital data to predict next week COVID-19 hospital admissions. We show that this hospital prediction model demonstrates a lower median absolute percentage error (MdAPE: 25.9%) across the five most populated regions in Sweden during the first pandemic wave than a model based on case notifications (MdAPE: 30.3%). During the second wave, the error rates are similar. When we apply the same model to an English dataset, not including local COVID-19 test data, we observe MdAPEs of 22.3% and 19.0% during the first and second pandemic waves, respectively, highlighting the transferability of the prediction model.

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  1. SciScore for 10.1101/2021.06.16.21258691: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

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    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    A limitation of the CSSS app is that, owing to limited resources, it is only available in Swedish, which precludes inclusion of non-Swedish speakers, who may be at high risk of COVID-19 infection 30. It is also possible that participants were more likely to join the study and report daily if they experienced symptoms associated with COVID-19 than if they were healthy, potentially inflating COVID-19 prevalence estimates. We sought to …