Risk of bias (quality) assessment

To assess the quality of the studies and the presence of risk of bias in the selected studies, the instrument known as the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) guidelines (14) was used. This assigns three categories (low, unclear, or high) for each item. The following factors were assessed: (A) Risk of bias: (i) Patient selection; (ii) Index test; (iii) Reference standard; (iv) Flow and timing. (B) Applicability concerns: (i) Patient selection; (ii) Index test; (iii) Reference standard.

Patient selection was considered in terms of how the patients were chosen for the study. The index test details the index test, including its administration and interpretation. The reference standard describes the reference standard (gold standard) and how it was carried out and interpreted. Finally, in the flow and timing section, it is explained whether there were patients who did not undergo the index tests or the reference standard, and it establishes the interval and any intervention between the index tests and the reference standard.