Predictive accuracy of a hierarchical logistic model of cumulative SARS-CoV-2 case growth until May 2020

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Abstract

Background

Infectious disease predictions models, including virtually all epidemiological models describing the spread of the SARS-CoV-2 pandemic, are rarely evaluated empirically. The aim of the present study was to investigate the predictive accuracy of a prognostic model for forecasting the development of the cumulative number of reported SARS-CoV-2 cases in countries and administrative regions worldwide until the end of May 2020.

Methods

The cumulative number of reported SARS-CoV-2 cases was forecasted in 251 regions with a horizon of two weeks, one month, and two months using a hierarchical logistic model at the end of March 2020. Forecasts were compared to actual observations by using a series of evaluation metrics.

Results

On average, predictive accuracy was very high in nearly all regions at the two weeks forecast, high in most regions at the one month forecast, and notable in the majority of the regions at the two months forecast. Higher accuracy was associated with the availability of more data for estimation and with a more pronounced cumulative case growth from the first case to the date of estimation. In some strongly affected regions, cumulative case counts were considerably underestimated.

Conclusions

With keeping its limitations in mind, the investigated model may be used for the preparation and distribution of resources during the initial phase of epidemics. Future research should primarily address the model’s assumptions and its scope of applicability. In addition, establishing a relationship with known mechanisms and traditional epidemiological models of disease transmission would be desirable.

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  1. SciScore for 10.1101/2020.06.15.20130989: (What is this?)

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

    Table 1: Rigor

    NIH rigor criteria are not applicable to paper type.

    Table 2: Resources

    No key resources detected.


    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).


    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    The presented evaluation study has several limitations. First, the case counts were not standardized in any form. Expressing them as cumulative incidence rates (e.g., per 100,000 persons) is likely to have increased homogeneity across regions and enhanced interpretability. As it has been shown in a specific analysis of the development of the SARS-CoV-2 epidemic in German federal states, standardization has rendered using log-transformation of case counts for homogenization superfluous and allowed estimating models with normally distributed errors.41 Second, in the present study uncertainty of the predictions remained unconsidered, although measures of uncertainty, such as reliability and sharpness, can be just as important for forecasting as bias.9 Third, predictions only at selected time points were analyzed, and it cannot be excluded that choosing other time points would have led to different results. Nevertheless, the general pattern of findings is unlikely to have changed substantially. The forecasting model itself has some weaknesses as well.31,41 Most importantly, it models the reported rather than the true number of cases and therefore can be subject to different forms of testing and reporting bias. Considerable improvement regarding this point can realistically be expected first when regional findings form well-conducted epidemiological studies become available. Another major limitation of the model is that it works only as long as the conditions of the epidemic remai...

    Results from TrialIdentifier: No clinical trial numbers were referenced.


    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.


    Results from JetFighter: We did not find any issues relating to colormaps.


    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

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