Table 1 Criteria for evaluating quality of reporting SMAs

Estimation of sample size

Statistical power; hypothesised effect estimate; effect size; alpha level; prevalence of exposure and probability of the expected outcome

All of these items reported for prospective studies.

For retrospective studies, post hoc power estimation or detectable difference

At least one item was not reported

No sample size estimation information provided

Follow-up time

Start and exit dates and aggregate follow-up time (median/person-time)

Reported all these items

At least one item was not reported

None of the items was reported

Survival curves

Number of patients at risk at the bottom of the graph; markings to indicate when participants were censored; axes were clearly labelled and used different colors/type of lines to distinguish curves

Reported all these items

At least one item was not reported

No survival curve was plotted

Comparison of survival curves

Methods for group comparisons and their test results (p-values)

Reported all these items

At least one item was not reported

No comparison was done

Reporting measures of effect in SAMs

Measures of effect and uncertainty among studies reporting regression analysis

Correct measure of effect and uncertainty reported

Incorrect measure of effect or no measure of uncertainty

No measure of effect and uncertainty reported

Test of survival regression models underlying assumptions

Survival regression models used; statistical method used to test underlying assumptions and test results

Reported all these items

At least one of the items not reported

All the items not reported

Analysis of hierarchical clustering

Presence of clustering; methods of investigating heterogeneity and correct method for adjustment

Test of investigating heterogeneity and correct method for adjustment where there was evidence of heterogeneity reported

At least one of the items not reported

No consideration for clustering