Table 2.

Tabular presentation of QUADAS-2¹⁶ results of the included studies.

Reference, first author	Risk of bias			Flow and timing	Applicability concerns			Overall risk	Author’s note
	Patient selection	Index test	Reference standard		Patient selection	Index test	Reference standard
Stidham RW17	☺☹	☺	☺	☹	☺	☹	☹	Low/ moderate	Small sample size, intra-individual comparison only, concerns about validation and reproducibility
Havre RF18	☺	☺	☺	☹	☺	☹	☺	Low	Small sample, the primary observer was not blinded, ex vivo setup
Dillman JR19	☺	☺	☹	?	☺	☺	☺	Low	Small sample size, ex vivo setup, single operator, concerns about validation and reproducibility
Baumgart DC20	☺	☺	☺	☹	☺	☺	☺	Low	Small sample size, inter- and intra-observer variability not assessed
Fraquelli M21	☺	☺	☺	☹	☹	☺	☺	Low	Small sample size, ultra-selected patients, concerns about validation and reproducibility
Giannetti A27	☹	☹	☺	?	☹	☺	☺	Moderate/ high	Case report, concerns about validation and reproducibility
Lu C22	☺	☺	☹	☺	☹	☺	☺	Low	Possible patients’ selection bias, two different US devices, concerns about validation
Serra C23	☺	☺	☹	☺	☺	☹	☺	Low	Small sample size, no control group, concerns about validation and reproducibility
Chen YJ24	☺	☺	☺	☹	☺	☺	☺	Low	Small sample size, intra-individual comparison only, concerns about validation
Quaia E25	☺	☺	☹	☺	☺	☺	☹	Low	Small sample size, concerns about the reference standard used, validation and reproducibility
Ding SS26	☺	☺	☹	☹	☺	☺	☹	Moderate	Small sample size, retrospective design, concerns about validation and reproducibility
Thimm MA28	☹	☹	☹	?	☹	☺	☺	Moderate/ High	Case report, concerns about validation and reproducibility

The QUADAS tool¹⁶ consists of four domains that assess: patient selection [was a consecutive or random sample of patients enrolled? was a case-control design avoided? did the study avoid inappropriate exclusions? could the selection of patients have introduced bias?]; index test [were the index test results interpreted without knowledge of the results of the reference standard? if a threshold was used, was it prespecified? could the conduct or interpretation of the index test have introduced bias?]; reference standard [is the reference standard likely to correctly classify the target condition? were the reference standard results interpreted without knowledge of the results of the index test?]; and flow of patients throughout the study design and timing of the index tests and reference standard [was there an appropriate interval between index tests and reference standard? did all patients receive a reference standard? did all patients receive the same reference standard? were all patients included in the analysis?].

US, ultrasound; ☺ low risk; ☹ high risk; ?, unclear.