Fig 1.
Inclusion flow.
Table 1.
Shown are the laboratory tests required for the CoLab-score and their mean/median results split by RT-PCR test result. For results with normal distributions, the mean value and standard deviation (in round brackets) are shown. For results that have skewed or heavy tailed distributions, the median value and the interquartile range is shown [in squared brackets]. The p-value corresponds to a t-test in cases of a normal distribution, a Man-Whitney U-test for non-normally distributed variables and a Fisher exact test for categorical variables.
Fig 2.
ROC curve of the CoLab-linear predictor.
The area under the ROC curve is shown with the 95% DeLong confidence interval in round brackets. The displayed threshold of -6.241 corresponds to a sensitivity of 100%, i.e. no HCWs below this linear predictor were RT-PCR positive.
Fig 3.
A. In the calibration plot the proportion of observed COVID-19 positives versus expected proportion of positives are plotted. Observations are grouped with an average of 50 observations per group. The expected probabilities follow from applying the inverse logit function to the CoLab-linear predictor. If the observed proportion in an external dataset is lower than the expected proportion, this means risks are over-estimated, if the observed fraction is higher, risks are under-estimated. Ideally, observed proportions are equal to expected proportions, this ideal-calibration-line is shown as a straight line through the origin with a slope of 1. The logistic calibration line is a logistic regression fit of the predicted probabilities. B. Using the intercept and/or slope from the logistic regression model, recalibrated probabilities were obtained and plotted in a second calibration plot.
Fig 4.
Histograms and fitted Gaussian distribution of the CoLab-linear predictor split by RT-PCR result.
A normal distribution was fitted to the RT-PCR negative group (mean: -6.04, SD: 1.73), the dashed lines represent the 95% CI. The 5th percentile of the Gaussian distribution is shown in red and dashed lines represent the 95% CI. Linear predictor values below this 5th percentile are regarded as non-COVID-19.
Fig 5.
CoLab-linear predictor versus RT-PCR CT value.
The CoLab-linear predictor is plotted versus the RT-PCR CT value. The red line is the CoLab-linear predictor cut-off below which HCWs are regarded as non-COVDI 19, the dashed red lines represent the 95% CI of the cut-off. The dashed line is a LOESS smooth where the 95% confidence interval is shown in gray.