Risk of bias assessment
The selected studies were heterogeneous, the overall risk of bias
assessment for the included studies is displayed in Figure 2 .
Within the patient selection domain, 43.6 % of studies showed high
risk, 31.5% showed low risk and 24.8% were of unclear risk of bias.
This originates from studies that did not randomly select, consecutively
enrol participants, use a case-control design, or not report how
exclusion was managed, highlighting the necessity to adhere to
standardized procedures. For applicability, 96.0% of studies had low
concerns that the included patients did not match the review question.
For the index test domain, 22.1% of studies showed high risk, 38.3%
low risk and 36.9% unclear risk of bias. The most common reasons for
assigning a high risk of bias were studies with a lack of blinding or
failure to establish a threshold for the index tests before conducting
the analysis. For applicability, 77.2% of studies had low concerns that
the index test, its conduct, or interpretation differed from the review
question.
For the reference standard domain, 18.1% of studies showed high risk of
bias, 38.9% low risk and 43.0% unclear risk. An increase in the risk
of bias was seen in studies which included prior information of the
reference standard test while performing the index test. For
applicability, 88.6% of studies had low concerns that the target
condition as defined by the reference standard does not match the review
question.
For the flow and timing domain, 61.1% of studies showed high risk,
23.5% low risk and 15.4% unclear risk of bias. We considered studies
to be of low risk of bias if all participants received the same
reference standard within six months of having received the index test.
Table 3 shows the risk of bias assessment summary for each
domain question and Table S4 shows the individual risk of bias
assessment per study.