Demographic and clinical characteristics of the three cohorts.

<p>Demographic and clinical characteristics of the three cohorts.</p

Multivariable logistic regression of symptoms of depression with age, sex and population as indicator.

<p>Multivariable logistic regression of symptoms of depression with age, sex and population as indicator.</p

Presentation of the results, stratified by type of prediction study.

<p>Numbers are column percentages, with absolute numbers in parentheses. Impact and external validation studies (<i>n</i> = 6) were excluded from this table as these items were not applicable. Hence, total <i>n</i> = 65.</p>a<p>The percentages do not add up to 100%, because studies reported univariable and multivariable models. Further, all studies reporting the full model also reported the final model.</p

Flowchart of included studies.

<p>^aThe hand search included only studies with an abstract, published in 2008 in <i>The New England Journal of Medicine</i>, <i>The Lancet</i>, <i>JAMA: the Journal of the American Medical Association</i>, <i>Annals of Internal Medicine</i>, <i>BMJ</i>, and <i>PLoS Medicine</i>. The following publication types were excluded beforehand: editorials, bibliographies, biographies, comments, dictionaries, directories, festschrifts, interviews, letters, news, and periodical indexes. ^bStudies, generally conducted in a yet healthy population, aimed at quantifying a causal relationship between a particular determinant or risk factor and an outcome, adjusting for other risk factors (i.e., confounders). ^cFor example, see <a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.1001221#pmed.1001221-Pletcher1" target="_blank">[72]</a>.</p

Handling of missing values, stratified by whether prediction was the primary or secondary study aim.

<p>Numbers are column percentages, with absolute numbers in parentheses.</p>a<p>Some studies reported more than one item. Hence, percentages do not add up to 100%.</p>b<p>Cross-sectional studies were excluded for this item (item not applicable).</p>c<p>More than one method could be applied. Hence, the percentages do not add up to 100%. Items were not applicable for two primary-aim studies that had no missing values. Hence, total <i>n</i> = 69.</p>d<p>Only participants with completely observed data were analysed.</p>e<p>For example: in a diagnostic study <a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.1001221#pmed.1001221-Imperiale1" target="_blank">[73]</a>, the investigators assumed that among participants who did not undergo follow-up colonoscopy, the detection rates for any adenoma and for an advanced adenoma ranged from half to twice the rates among participants who did undergo follow-up colonoscopy.</p

Reporting of outcomes.

<p>Impact studies were excluded from this table because these studies had outcomes of a different type (e.g., costs). Hence, the total number of studies is 68.</p>a<p>Not applicable in 11/68 studies, because all cause death was the outcome.</p>b<p>Types of outcomes and how they were analysed (unclear for five studies). The sum 6+23+8+30 is higher than 63 because some outcomes were analysed in more than one way (e.g., a time-to-event outcome that was analysed as time to event and as a binary outcome neglecting time). If a study analysed two binary outcomes, it was here counted as one binary outcome.</p>c<p>After dichotomization of a continuous outcome.</p>d<p>One study used the Cochran–Mantel–Haenszel procedure, another calculated odds ratios.</p><p>CART, classification and regression tree.</p

Method of predictor selection, stratified by whether prediction was the primary or secondary study aim.

<p>Numbers are column percentages, with absolute numbers in parentheses. Impact and external validation studies (<i>n</i> = 6) were excluded from this table as these issues are not applicable for these type of studies. Hence, <i>n</i> = 65.</p>a<p>More than one method may be used within a study; percentages do not add up to 100%.</p>b<p>Percentage (number) of studies that reported the applied method for selecting which predictors were included in the multivariable analyses, if it was not based on statistical analysis (i.e., univariable predictor–outcome associations).</p>c<p>Predictor inclusion in multivariable model was pre-specified, as the specific aim was to quantify the added value of a new predictor to existing predictors.</p>d<p>For example, systolic and diasystolic blood pressure combined to mean blood pressure.</p>e<p>For the items below, two percentages are given. The first percentage includes all studies (i.e., 48 predictor finding studies, 17 model development studies, or 65 total); the second is the percentage of all studies that applied some type of predictor selection in the multivariable analysis (35 predictor finding studies, 11 model development studies, and 46 total; the excluded studies did not apply any predictor selection in the multivariable analysis but simply pre-specified the final model).</p

Reporting of candidate predictors.

<p>Impact studies (<i>n</i> = 3) were excluded from this table as their aim is not to develop or validate a prediction model, but rather to quantify the effect or impact of using a prediction model on physicians' behaviour, patient outcome, or cost-effectiveness of care relative to not using the model or usual care. Hence, for this table total <i>n</i> = 68.</p>a<p>Not applicable for the three external validation studies. Hence, <i>n</i> = 65.</p>b<p>Not applicable in four studies, because one studied no continuous predictors, and the others were the three external validation studies. Hence, <i>n</i> = 64. Of these, handling was unclear in 19 studies, not described in two studies. The sum 43+12+30+21+2 is more than 43 because some studies handled continuous predictors in two ways (e.g., dichotomizing blood pressure and categorising body mass index into four categories).</p

Characteristics of the study cohort.

<p>LL: lacunar lesion. ATR: anterior thalamic radiation. SLF: superior longitudinal fasciculus. WML: white matter lesion.</p>a<p>Adds up to >100% because some patients had multiple diagnoses at inclusion.</p>b<p>Data are based on volumes after registration to MNI space (normalised volumes).</p>c<p>Among 98 patients with a LL.</p

Model performance measures, stratified by type of prediction study.

<p>Numbers are column percentages, with absolute numbers in parentheses. The percentages sometimes do not add up to 100% because development studies commonly reported more than one performance measure or validity assessment.</p>a<p>Impact studies (<i>n</i> = 3) were excluded since all items were not applicable. Additionally, two external validation studies were excluded because they evaluated risk stratification tools that did not provide predicted probabilities (the Manchester triage system <a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.1001221#pmed.1001221-VanVeen1" target="_blank">[74]</a> and predictive life support tools <a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.1001221#pmed.1001221-Sasson1" target="_blank">[75]</a>). Hence, almost all items were not applicable. Hence, for this table total <i>n</i> = 66 studies.</p>b<p>The predictive performance (e.g., <i>C</i>-statistic, calibration, or net reclassification index) of the prediction model as estimated from the same data from which the model was developed.</p><p>AUC-ROC, area under the receiver operation characteristic curve; NRI, net reclassification index.</p