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| Phase | Clinical question | Objective(s) | Statistics for results | Example (ref.) |
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| I | Which are the normal ranges of values of a diagnostic test? | Determination of the range of values on healthy subjects | Centrality and dispersion (descriptive) metrics:
(i) mean (SD), where SD = standard deviation, if data follow the normal distribution;
(ii) otherwise, median (Q1 − Q3), where Q1 = 25th percentile and Q3 = 75th percentiles | (i) Levels of hepcidin and prohepcidin in healthy subjects [93]
(ii) plasma pro-gastrin-releasing peptide (ProGRP) levels in healthy adults [94] |
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| I | Is the test reproducible? | Variability:
(i) Intra- and interobserver
(ii) Intra- and interlaboratory | (i) Agreement analysis: % (95% confidence interval) and agreement coefficients (dichotomial data: Cohen, ordinal data: weighted kappa, numerical: Lin’s concordance correlation coefficient, and Bland and Altman diagram)
(ii) Variability analysis: Coefficient of variation, distribution of differences | (i) Intra- and interobserver variability of uterine measurements [95]
(ii) Interlaboratory variability of cervical cytopathology [96]
(iii) Concordance between tuberculin skin test and QuantiFERON in children [40] |
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| II | Is the test accurate? Which are performances of the diagnostic test? | Determine the accuracy as compared to a gold standard test | (i) Metrics (dichotomial outcome): Se (sensitivity), Sp (specificity), PPV (predictive positive value), NPV (negative predictive value), and DOR (diagnostic odds ratio)
(ii) Clinical performances (dichotomial outcome): PLR (positive likelihood ratio) and NLR (negative likelihood ratio)
(iii) Threshold identification (numerical or ordinal with a minimum of five classes outcome): ROC (receiver operating characteristic curve) analysis | (i) Digital breast tomosynthesis for benign and malignant lesions in breasts [97]
(ii) Chitotriosidase as a marker of inflammatory status in critical limb ischemia [59]
(iii) Sonoelastographic scores to discriminate between benign and malignant cervical lymph nodes [45] |
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| III | Which are the costs, risk, and acceptability of a diagnostic test? | (i) Evaluation of beneficial and harmful effects
(ii) Cost-effective analysis | Retrospective or prospective studies:
(i) beneficial (e.g., improvement of clinical outcome) or harmful effects (e.g., morbidity and mortality) by proportions, risk ratio, odds ratio, hazard ratio, the number needed to treat, and rates and ratios of desirable or undesirable outcomes
(ii) cost-effective analysis (mean cost and quality-adjusted life years (QALYs)) | (i) The computed tomography in children, the associated radiation exposure, and the risk of cancer [98]
(ii) Healthcare benefit and cost-effectiveness of a screening strategy for colorectal cancer [99] |
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| IV | Which are the consequences of introducing a new diagnostic test into clinical practice? | (i) Does the test result affect the clinical decision? | (i) Studies of pre- and posttest clinical decision-making
(ii) %: abnormal, of discrepant results, of tests leading to change the clinical decisions
(iii) Costs: per abnormal result, decision change | (i) Does the interferon-gamma release assays (IGRAs) change the clinical management of patients with latent tuberculosis infection (LTBI)? [100] |
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