Abstract
If and how the increasing numbers in confirmed COVID 19 cases are driven
by the simultaneous expansion of test capacities and tests conducted is
a question under continuous debate. Building on the hypothesis, that the
impact of increased testing might not be constant over time but
determined by the national test policy applied, the relationship between
testing and number of cases was investigated in different phases of the
pandemic with a focus on the time before and after a change in German
legislation on May 22, 2020 that opened the door for more tests in
asymptomatic persons for prevention and containment purposes. Based on
linear regression models it is estimated that about 60% of the cases
tested positive after May 22 can be attributed to increased testing,
while eliminating the test effect does not substantially impact the
numbers before that date. Likewise, the clinical presentation of cases
registered after May 22 is significantly different, with a
hospitalization rate of 8.12% (before 18.17%) and a case fatality rate
of 0.63% (before 5.17%).
It is concluded that expanding the number of tests as it was done in
Germany did not lead to a better understanding of the epidemiology of
COVID 19. It is recommended to separate test results from preventive
testing and testing based on a clinically defined test strategy, and to
only use the latter for surveillance and as a basis for political
decisions.