Additional file 2: of Predictors for independent external validation of cardiovascular risk clinical prediction rules: Cox proportional hazards regression analyses

Journals that published derivation and independent external validation studies. (DOCX 121 kb

Why do authors derive new cardiovascular clinical prediction rules in the presence of existing rules? A mixed methods study

<div><p>Background</p><p>Researchers should examine existing evidence to determine the need for a new study. It is unknown whether developers evaluate existing evidence to justify new cardiovascular clinical prediction rules (CPRs).</p><p>Objective</p><p>We aimed to assess whether authors of cardiovascular CPRs cited existing CPRs, why some authors did not cite existing CPRs, and why they thought existing CPRs were insufficient.</p><p>Method</p><p>Derivation studies of cardiovascular CPRs from the International Register of Clinical Prediction Rules for Primary Care were evaluated. We reviewed the introduction sections to determine whether existing CPRs were cited. Using thematic content analysis, the stated reasons for determining existing cardiovascular CPRs insufficient were explored. Study authors were surveyed via e-mail and post. We asked whether they were aware of any existing cardiovascular CPRs at the time of derivation, how they searched for existing CPRs, and whether they thought it was important to cite existing CPRs.</p><p>Results</p><p>Of 85 derivation studies included, 48 (56.5%) cited existing CPRs, 33 (38.8%) did not cite any CPR, and four (4.7%) declared there was none to cite. Content analysis identified five categories of existing CPRs insufficiency related to: (1) derivation (5 studies; 11.4% of 44), (2) construct (31 studies; 70.5%), (3) performance (10 studies; 22.7%), (4) transferability (13 studies; 29.5%), and (5) evidence (8 studies; 18.2%). Authors of 54 derivation studies (71.1% of 76 authors contacted) responded to the survey. Twenty-five authors (46.3%) reported they were aware of existing CPR at the time of derivation. Twenty-nine authors (53.7%) declared they conducted a systematic search to identify existing CPRs. Most authors (90.7%) indicated citing existing CPRs was important.</p><p>Conclusion</p><p>Cardiovascular CPRs are often developed without citing existing CPRs although most authors agree it is important. Common justifications for new CPRs concerned construct, including choice of predictor variables or relevance of outcomes. Developers should clearly justify why new CPRs are needed with reference to existing CPRs to avoid unnecessary duplication.</p></div

Flow diagram.

<p>Flow diagram.</p

Survey responses according to the citation of existing cardiovascular prediction rule.

<p>Survey responses according to the citation of existing cardiovascular prediction rule.</p

Influence of design characteristics on the performance of clinical prediction rule in multivariable analysis.

<p>Influence of design characteristics on the performance of clinical prediction rule in multivariable analysis.</p

Quality of reporting.

<p>Proportion of validation studies with adequate and inadequate description of reporting characteristics.</p

Fagan nomogram.

<p>Applying the sensitivity and specificity of (a) 90% as presented in the validation study [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0145779#pone.0145779.ref058" target="_blank">58</a>] and (b) 81% from an unbiased study to a patient with 10% probability of rheumatoid arthritis.</p

Evolution of methodological quality over time.

<p>Proportion of validation studies satisfying (a) reporting characteristics and (b) design characteristics recommended in methodological standards.</p