A simple checklist with a small number of key domains was designed to critically appraise the study biases, including methodological domains of participant selection, outcome measurement, exposure measurement, control for confounding and appropriate analysis.
To assess the quality of the study design, we used a modified Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS 2) tool [ 9, 10], as it separately assesses risk of bias in several methodological domains (patient selection, index test, reference test and patient flow) using a number of signalling questions (Table 1).
Given the poor agreement on the use of summary scores and checklists, the quality of the included studies was assessed individually, by methodological domain.
Each study type was judged within its methodological domain.
Hence, each study design is judged within its methodological domain (table 1).
The majority of the methodological quality domains of random sequence generation (52.3%), allocation concealment (39.6%) and blinding (22.2%) were reported inadequately.
In the current review, the quality of included studies was assessed using the Critical Appraisal Skills Program critical appraisal checklists, which address the key domains of methodological quality.
One of us (YY) presented, domain by domain, each type of methodological problem and proposed adjustments, with detailed examples from the trials in the sample.
Using the COSMIN checklist [ 12] and the 4-point rating scale according to Terwee et al. [ 13], overall scores of methodological quality for each measurement domain were obtained.
