"Rule out appendicitis": a Canadian emergency radiology perspective on medicolegal risks, imaging pitfalls, and strategies to improve care.

We provide a unique Canadian perspective on the medicolegal risks associated with imaging acute appendicitis, incorporating data requested from the Canadian Medical Protective Association (CMPA) on closed medicolegal cases over the past decade. We include a review of current clinical and imaging guidelines in the diagnosis and management of this common emergency room presentation. A case-based approach is implemented in this article to explore ways to mitigate potential errors in the diagnosis of acute appendicitis.

Thoracic imaging tests for the diagnosis of COVID-19.

BACKGROUND: Our March 2021 edition of this review showed thoracic imaging computed tomography (CT) to be sensitive and moderately specific in diagnosing COVID-19 pneumonia. This new edition is an update of the review. OBJECTIVES: Our objectives were to evaluate the diagnostic accuracy of thoracic imaging in people with suspected COVID-19; assess the rate of positive imaging in people who had an initial reverse transcriptase polymerase chain reaction (RT-PCR) negative result and a positive RT-PCR result on follow-up; and evaluate the accuracy of thoracic imaging for screening COVID-19 in asymptomatic individuals. The secondary objective was to assess threshold effects of index test positivity on accuracy. SEARCH METHODS: We searched the COVID-19 Living Evidence Database from the University of Bern, the Cochrane COVID-19 Study Register, The Stephen B. Thacker CDC Library, and repositories of COVID-19 publications through to 17 February 2021. We did not apply any language restrictions. SELECTION CRITERIA: We included diagnostic accuracy studies of all designs, except for case-control, that recruited participants of any age group suspected to have COVID-19. Studies had to assess chest CT, chest X-ray, or ultrasound of the lungs for the diagnosis of COVID-19, use a reference standard that included RT-PCR, and report estimates of test accuracy or provide data from which we could compute estimates. We excluded studies that used imaging as part of the reference standard and studies that excluded participants with normal index test results. DATA COLLECTION AND ANALYSIS: The review authors independently and in duplicate screened articles, extracted data and assessed risk of bias and applicability concerns using QUADAS-2. We presented sensitivity and specificity per study on paired forest plots, and summarized pooled estimates in tables. We used a bivariate meta-analysis model where appropriate. MAIN RESULTS: We included 98 studies in this review. Of these, 94 were included for evaluating the diagnostic accuracy of thoracic imaging in the evaluation of people with suspected COVID-19. Eight studies were included for assessing the rate of positive imaging in individuals with initial RT-PCR negative results and positive RT-PCR results on follow-up, and 10 studies were included for evaluating the accuracy of thoracic imaging for imagining asymptomatic individuals. For all 98 included studies, risk of bias was high or unclear in 52 (53%) studies with respect to participant selection, in 64 (65%) studies with respect to reference standard, in 46 (47%) studies with respect to index test, and in 48 (49%) studies with respect to flow and timing. Concerns about the applicability of the evidence to: participants were high or unclear in eight (8%) studies; index test were high or unclear in seven (7%) studies; and reference standard were high or unclear in seven (7%) studies. Imaging in people with suspected COVID-19 We included 94 studies. Eighty-seven studies evaluated one imaging modality, and seven studies evaluated two imaging modalities. All studies used RT-PCR alone or in combination with other criteria (for example, clinical signs and symptoms, positive contacts) as the reference standard for the diagnosis of COVID-19. For chest CT (69 studies, 28285 participants, 14,342 (51%) cases), sensitivities ranged from 45% to 100%, and specificities from 10% to 99%. The pooled sensitivity of chest CT was 86.9% (95% confidence interval (CI) 83.6 to 89.6), and pooled specificity was 78.3% (95% CI 73.7 to 82.3). Definition for index test positivity was a source of heterogeneity for sensitivity, but not specificity. Reference standard was not a source of heterogeneity. For chest X-ray (17 studies, 8529 participants, 5303 (62%) cases), the sensitivity ranged from 44% to 94% and specificity from 24 to 93%. The pooled sensitivity of chest X-ray was 73.1% (95% CI 64. to -80.5), and pooled specificity was 73.3% (95% CI 61.9 to 82.2). Definition for index test positivity was not found to be a source of heterogeneity. Definition for index test positivity and reference standard were not found to be sources of heterogeneity. For ultrasound of the lungs (15 studies, 2410 participants, 1158 (48%) cases), the sensitivity ranged from 73% to 94% and the specificity ranged from 21% to 98%. The pooled sensitivity of ultrasound was 88.9% (95% CI 84.9 to 92.0), and the pooled specificity was 72.2% (95% CI 58.8 to 82.5). Definition for index test positivity and reference standard were not found to be sources of heterogeneity. Indirect comparisons of modalities evaluated across all 94 studies indicated that chest CT and ultrasound gave higher sensitivity estimates than X-ray (P = 0.0003 and P = 0.001, respectively). Chest CT and ultrasound gave similar sensitivities (P=0.42). All modalities had similar specificities (CT versus X-ray P = 0.36; CT versus ultrasound P = 0.32; X-ray versus ultrasound P = 0.89). Imaging in PCR-negative people who subsequently became positive For rate of positive imaging in individuals with initial RT-PCR negative results, we included 8 studies (7 CT, 1 ultrasound) with a total of 198 participants suspected of having COVID-19, all of whom had a final diagnosis of COVID-19. Most studies (7/8) evaluated CT. Of 177 participants with initially negative RT-PCR who had positive RT-PCR results on follow-up testing, 75.8% (95% CI 45.3 to 92.2) had positive CT findings. Imaging in asymptomatic PCR-positive people For imaging asymptomatic individuals, we included 10 studies (7 CT, 1 X-ray, 2 ultrasound) with a total of 3548 asymptomatic participants, of whom 364 (10%) had a final diagnosis of COVID-19. For chest CT (7 studies, 3134 participants, 315 (10%) cases), the pooled sensitivity was 55.7% (95% CI 35.4 to 74.3) and the pooled specificity was 91.1% (95% CI 82.6 to 95.7). AUTHORS' CONCLUSIONS: Chest CT and ultrasound of the lungs are sensitive and moderately specific in diagnosing COVID-19. Chest X-ray is moderately sensitive and moderately specific in diagnosing COVID-19. Thus, chest CT and ultrasound may have more utility for ruling out COVID-19 than for differentiating SARS-CoV-2 infection from other causes of respiratory illness. The uncertainty resulting from high or unclear risk of bias and the heterogeneity of included studies limit our ability to confidently draw conclusions based on our results.

Association of Accuracy, Conclusions, and Reporting Completeness With Acceptance by Radiology Conferences and Journals.

BACKGROUND: Preferential publication of studies with positive findings can lead to overestimation of diagnostic test accuracy (i.e. publication bias). Understanding the contribution of the editorial process to publication bias could inform interventions to optimize the evidence guiding clinical decisions. PURPOSE/HYPOTHESIS: To evaluate whether accuracy estimates, abstract conclusion positivity, and completeness of abstract reporting are associated with acceptance to radiology conferences and journals. STUDY TYPE: Meta-research. POPULATION: Abstracts submitted to radiology conferences (European Society of Gastrointestinal and Abdominal Radiology (ESGAR) and International Society for Magnetic Resonance in Medicine (ISMRM)) from 2008 to 2018 and manuscripts submitted to radiology journals (Radiology, Journal of Magnetic Resonance Imaging [JMRI]) from 2017 to 2018. Primary clinical studies evaluating sensitivity and specificity of a diagnostic imaging test in humans with available editorial decisions were included. ASSESSMENT: Primary variables (Youden's index [YI > 0.8 vs. <0.8], abstract conclusion positivity [positive vs. neutral/negative], number of reported items on the Standards for Reporting of Diagnostic Accuracy Studies [STARD] for Abstract guideline) and confounding variables (prospective vs. retrospective/unreported, sample size, study duration, interobserver agreement assessment, subspecialty, modality) were extracted. STATISTICAL TESTS: Multivariable logistic regression to obtain adjusted odds ratio (OR) as a measure of the association between the primary variables and acceptance by radiology conferences and journals; 95% confidence intervals (CIs) and P-values were obtained; the threshold for statistical significance was P < 0.05. RESULTS: A total of 1000 conference abstracts (500 ESGAR and 500 ISMRM) and 1000 journal manuscripts (505 Radiology and 495 JMRI) were included. Conference abstract acceptance was not significantly associated with YI (adjusted OR = 0.97 for YI > 0.8; CI = 0.70-1.35), conclusion positivity (OR = 1.21 for positive conclusions; CI = 0.75-1.90) or STARD for Abstracts adherence (OR = 0.96 per unit increase in reported items; CI = 0.82-1.18). Manuscripts with positive abstract conclusions were less likely to be accepted by radiology journals (OR = 0.45; CI = 0.24-0.86), while YI (OR = 0.85; CI = 0.56-1.29) and STARD for Abstracts adherence (OR = 1.06; CI = 0.87-1.30) showed no significant association. Positive conclusions were present in 86.7% of submitted conference abstracts and 90.2% of journal manuscripts. DATA CONCLUSION: Diagnostic test accuracy studies with positive findings were not preferentially accepted by the evaluated radiology conferences or journals. EVIDENCE LEVEL: 3 TECHNICAL EFFICACY: Stage 2.

Tweeting Bias in Diagnostic Test Accuracy Research: Does Title or Conclusion Positivity Influence Dissemination?

PURPOSE: To examine if tweeting bias exists within imaging literature by determining if diagnostic test accuracy (DTA) studies with positive titles or conclusions are tweeted more than non-positive studies. METHODS: DTA studies published between October 2011 to April 2016 were included. Positivity of titles and conclusions were assessed independently and in duplicate, with disagreements resolved by consensus. A negative binomial regression analysis controlling for confounding variables was performed to assess the relationship between title or conclusion positivity and tweets an article received in the 100 days post-publication. RESULTS: 354 DTA studies were included. Twenty-four (7%) titles and 300 (85%) conclusions were positive (or positive with qualifier); 1 (0.3%) title and 23 (7%) conclusions were negative; and 329 (93%) titles and 26 (7%) conclusions were neutral. Studies with positive, negative, and neutral titles received a mean of 0.38, 0.00, and 0.45 tweets per study; while those with positive, negative, and neutral conclusions received a mean of 0.44, 0.61, and 0.38 tweets per study. Regression coefficients were -0.05 (SE 0.46) for positive relative to non-positive titles, and -0.09 (SE 0.31) for positive relative to non-positive conclusions. The positivity of the title (P = 0.91) or conclusion (P = 0.76) was not significantly associated with the number of tweets an article received. CONCLUSIONS: The positivity of the title or conclusion for DTA studies does not influence the amount of tweets it receives suggesting that tweet bias is not present among imaging diagnostic accuracy studies. Study protocol available at https://osf.io/hdk2m/.

Thoracic imaging tests for the diagnosis of COVID-19.

BACKGROUND: The respiratory illness caused by SARS-CoV-2 infection continues to present diagnostic challenges. Our 2020 edition of this review showed thoracic (chest) imaging to be sensitive and moderately specific in the diagnosis of coronavirus disease 2019 (COVID-19). In this update, we include new relevant studies, and have removed studies with case-control designs, and those not intended to be diagnostic test accuracy studies. OBJECTIVES: To evaluate the diagnostic accuracy of thoracic imaging (computed tomography (CT), X-ray and ultrasound) in people with suspected COVID-19. SEARCH METHODS: We searched the COVID-19 Living Evidence Database from the University of Bern, the Cochrane COVID-19 Study Register, The Stephen B. Thacker CDC Library, and repositories of COVID-19 publications through to 30 September 2020. We did not apply any language restrictions. SELECTION CRITERIA: We included studies of all designs, except for case-control, that recruited participants of any age group suspected to have COVID-19 and that reported estimates of test accuracy or provided data from which we could compute estimates. DATA COLLECTION AND ANALYSIS: The review authors independently and in duplicate screened articles, extracted data and assessed risk of bias and applicability concerns using the QUADAS-2 domain-list. We presented the results of estimated sensitivity and specificity using paired forest plots, and we summarised pooled estimates in tables. We used a bivariate meta-analysis model where appropriate. We presented the uncertainty of accuracy estimates using 95% confidence intervals (CIs). MAIN RESULTS: We included 51 studies with 19,775 participants suspected of having COVID-19, of whom 10,155 (51%) had a final diagnosis of COVID-19. Forty-seven studies evaluated one imaging modality each, and four studies evaluated two imaging modalities each. All studies used RT-PCR as the reference standard for the diagnosis of COVID-19, with 47 studies using only RT-PCR and four studies using a combination of RT-PCR and other criteria (such as clinical signs, imaging tests, positive contacts, and follow-up phone calls) as the reference standard. Studies were conducted in Europe (33), Asia (13), North America (3) and South America (2); including only adults (26), all ages (21), children only (1), adults over 70 years (1), and unclear (2); in inpatients (2), outpatients (32), and setting unclear (17). Risk of bias was high or unclear in thirty-two (63%) studies with respect to participant selection, 40 (78%) studies with respect to reference standard, 30 (59%) studies with respect to index test, and 24 (47%) studies with respect to participant flow. For chest CT (41 studies, 16,133 participants, 8110 (50%) cases), the sensitivity ranged from 56.3% to 100%, and specificity ranged from 25.4% to 97.4%. The pooled sensitivity of chest CT was 87.9% (95% CI 84.6 to 90.6) and the pooled specificity was 80.0% (95% CI 74.9 to 84.3). There was no statistical evidence indicating that reference standard conduct and definition for index test positivity were sources of heterogeneity for CT studies. Nine chest CT studies (2807 participants, 1139 (41%) cases) used the COVID-19 Reporting and Data System (CO-RADS) scoring system, which has five thresholds to define index test positivity. At a CO-RADS threshold of 5 (7 studies), the sensitivity ranged from 41.5% to 77.9% and the pooled sensitivity was 67.0% (95% CI 56.4 to 76.2); the specificity ranged from 83.5% to 96.2%; and the pooled specificity was 91.3% (95% CI 87.6 to 94.0). At a CO-RADS threshold of 4 (7 studies), the sensitivity ranged from 56.3% to 92.9% and the pooled sensitivity was 83.5% (95% CI 74.4 to 89.7); the specificity ranged from 77.2% to 90.4% and the pooled specificity was 83.6% (95% CI 80.5 to 86.4). For chest X-ray (9 studies, 3694 participants, 2111 (57%) cases) the sensitivity ranged from 51.9% to 94.4% and specificity ranged from 40.4% to 88.9%. The pooled sensitivity of chest X-ray was 80.6% (95% CI 69.1 to 88.6) and the pooled specificity was 71.5% (95% CI 59.8 to 80.8). For ultrasound of the lungs (5 studies, 446 participants, 211 (47%) cases) the sensitivity ranged from 68.2% to 96.8% and specificity ranged from 21.3% to 78.9%. The pooled sensitivity of ultrasound was 86.4% (95% CI 72.7 to 93.9) and the pooled specificity was 54.6% (95% CI 35.3 to 72.6). Based on an indirect comparison using all included studies, chest CT had a higher specificity than ultrasound. For indirect comparisons of chest CT and chest X-ray, or chest X-ray and ultrasound, the data did not show differences in specificity or sensitivity. AUTHORS' CONCLUSIONS: Our findings indicate that chest CT is sensitive and moderately specific for the diagnosis of COVID-19. Chest X-ray is moderately sensitive and moderately specific for the diagnosis of COVID-19. Ultrasound is sensitive but not specific for the diagnosis of COVID-19. Thus, chest CT and ultrasound may have more utility for excluding COVID-19 than for differentiating SARS-CoV-2 infection from other causes of respiratory illness. Future diagnostic accuracy studies should pre-define positive imaging findings, include direct comparisons of the various modalities of interest in the same participant population, and implement improved reporting practices.

Safety of Off-Label Use of Ferumoxtyol as a Contrast Agent for MRI: A Systematic Review and Meta-Analysis of Adverse Events.

BACKGROUND: Ferumoxytol has been studied as an alternative to gadolinium-based MRI contrast agents, but regulatory body warnings currently limit its use. PURPOSE: Estimate the adverse event rate in patients undergoing MRI with ferumoxytol as a contrast agent. STUDY TYPE: Systematic review. POPULATION: Thirty-nine studies including 5411 ferumoxytol administrations in 4336 patients. ASSESSMENT: Multiple databases were searched for studies using ferumoxytol as an off-label MRI contrast agent in any patient population as of April 2020. Studies were eligible for inclusion if they reported the number and severity of adverse events (classified by American College of Radiology [ACR] severity of acute reactions). Risk of bias was assessed using the ROBINS-I tool. STATISTICAL TESTS: The proportion of administrations with adverse events was calculated using random effects meta-analysis of proportions. RESULTS: No deaths related to ferumoxytol administration were reported. Sixteen studies reported immediate adverse events in 3849 patients undergoing 4901 ferumoxytol administrations. Ninety-seven immediate adverse events were reported and the pooled adverse event proportion for immediate adverse events was 0.02 (95% confidence interval [CI] 0.02-0.02). Twenty-three studies reported time-unspecified adverse events in 487 patients undergoing 510 ferumoxytol administrations. Five time-unspecified adverse events were reported; the pooled adverse event proportion for time-unspecified adverse events was 0.01 (95% CI 0.00-0.04). 88% of adverse events were mild (90/102), 11% (11/102) were moderate, and 1% (1/102) was severe. Sixteen studies were at low risk of bias, 23 studies were at serious risk of bias. Subgroup analysis by patient population revealed no significant variability (adult vs. pediatric). No studies evaluated the use of ferumoxytol as an alternative to patients who had a prior hypersensitivity reaction to gadolinium-based contrast agents (GBCAs). DATA CONCLUSION: The overall adverse event rate for off-label ferumoxytol use as an MRI contrast agent is 2%, with rare severe reactions and no deaths. To date, there are no studies evaluating the safety of ferumoxytol as an alternative to GBCAs in patients with a prior hypersensitivity reaction. LEVEL OF EVIDENCE: 2 TECHNICAL EFFICACY STAGE: 5.

Reporting Bias in Imaging Diagnostic Test Accuracy Studies: Are Studies With Positive Conclusions or Titles Submitted and Published Faster?

OBJECTIVE: The purpose of this study is to evaluate whether imaging diagnostic test accuracy (DTA) studies with positive conclusions or titles have a shorter time to publication than those with nonpositive (i.e., negative or neutral) conclusions or titles. MATERIALS AND METHODS: We included primary imaging DTA studies from systematic reviews published in 2015. The conclusion and title of each study were extracted, and their positivity was classified independently in duplicate. The time from study completion to publication was extracted and calculated. A Cox regression model was used to evaluate associations of conclusion and title positivity with time to publication, with adjustment made for potentially confounding variables. RESULTS: A total of 774 imaging DTA studies were included; time from study completion to publication could be calculated for 516 studies. The median time from completion to publication was 18 months (interquartile range, 13-26 months) for the 413 studies with positive conclusions, 23 months (interquartile range, 16-33 months) for the 63 studies with neutral conclusions, and 25 months (interquartile range, 15-38 months) for the 40 studies with negative conclusions. A positive conclusion was associated with a shorter time from study completion to publication compared with a non-positive conclusion (hazard ratio, 1.31; 95% CI, 1.02-1.68). Of all included studies, 39 (5%) had positive titles, 731 (94%) had neutral titles, and 4 (< 1%) had negative titles. Positive titles were not significantly associated with a shorter time to study publication (hazard ratio, 1.12; 95% CI, 0.75-1.69). CONCLUSION: Positive conclusions (but not titles) were associated with a shorter time from study completion to publication. This finding may contribute to an overrepresentation of positive results in the imaging DTA literature.

Overinterpretation of Research Findings: Evaluation of "Spin" in Systematic Reviews of Diagnostic Accuracy Studies in High-Impact Factor Journals.

BACKGROUND: To compare the frequency of "spin" in systematic reviews of diagnostic accuracy studies in high-impact journals with the frequency a previously assessed series of reviews. METHODS: Medline was searched from January 2010 to January 2019. Systematic reviews of diagnostic accuracy studies were included if they reported a meta-analysis and were published in a journal with an impact factor >5. Two investigators independently scored each included systematic review for positivity of conclusions and for actual and potential overinterpretation practices. RESULTS: Of 137 included systematic reviews, actual overinterpretation was present in ≥1 form in the abstract in 63 (46%) and in the full-text report in 52 (38%); 108 (79%) contained a form of potential overinterpretation. Compared with the previously assessed series (reviews published 2015-2016), reviews in this series were less likely to contain ≥1 form of actual overinterpretation in the abstract and full-text report or ≥1 form of potential overinterpretation (P < 0.001 for all comparisons). The significance of these comparisons did not persist for actual overinterpretation in sensitivity analysis in which Cochrane systematic reviews were removed. Reviews published in the Cochrane Database of Systematic Reviews were less likely to contain actual overinterpretation in the abstract or the full-text report than reviews in other high-impact journals (P < 0.001 for both comparisons). CONCLUSIONS: Reviews of diagnostic accuracy studies in high-impact journals are less likely to contain overinterpretation or spin. This difference is largely due to the reviews published in the Cochrane Database of Systematic Reviews, which contain spin less often than reviews published in other high-impact journals.

Publication bias in diagnostic imaging: conference abstracts with positive conclusions are more likely to be published.

OBJECTIVE: To evaluate whether imaging diagnostic test accuracy conference abstracts with positive conclusions or titles are more likely to reach full-text publication than those with negative (or neutral) conclusions or titles. METHODS: Diagnostic accuracy research abstracts were included if they were presented at the 2011 or 2012 Radiological Society of North America conference. Full-text publication status at 5 years post conference abstract submission was determined. Conclusion and title positivity of conference abstracts were extracted, as well as potential confounding factors. The associations of conclusion and title positivity with publication status at 5 years post conference abstract submission were assessed using a multivariable logistic regression model. Conditional odds ratios were calculated to express the strength of associations, adjusting for the confounders. RESULTS: In total, 282/400 (71%) of included conference abstracts reached full-text publication. A total of 246 out of 337 (74%) conference abstracts with positive conclusions resulted in full-text publications, compared with 26/48 (54%) with neutral conclusions and 5/15 (33%) with negative conclusions. In multivariable logistic regression, conclusion positivity was significantly associated with full-text publication (odds ratio 3.6; 95% CI 1.9-6.7 for conference abstracts with positive conclusions, compared with those with non-positive conclusions); this did not apply to title positivity (odds ratio 1.2; 95% CI 0.47-3.0). CONCLUSION: Imaging conference abstracts with positive conclusions were more likely to be published as full-text articles. Title positivity was not associated with publication. This preferential publication pattern may lead to an overrepresentation of positive studies in the literature. An overrepresentation of positive studies may contribute to inflated estimates of test accuracy and has the potential to adversely influence patient care. KEY POINTS: • Imaging diagnostic test accuracy conference abstracts with positive conclusions were more likely to be reported as full-text articles than those with non-positive conclusions. • The majority (75%) of imaging diagnostic test accuracy conference abstracts with positive conclusions were published, compared with only 53% and 33% with neutral and negative conclusions, respectively. • Conclusion positivity remained associated with the full-text publication of conference abstracts when controlling for multiple potential confounding variables.

Selective Citation Practices in Imaging Research: Are Diagnostic Accuracy Studies With Positive Titles and Conclusions Cited More Often?

OBJECTIVE. The purpose of this study was to examine the existence of selective citation practices in the imaging literature by assessing whether diagnostic accuracy studies with positive titles or conclusions are cited more frequently than those with negative (or neutral) titles or conclusions. MATERIALS AND METHODS. MEDLINE was searched for meta-analyses of diagnostic accuracy studies published in imaging journals from January 2005 to April 2016. Primary studies from the meta-analyses were screened for eligibility. Titles and conclusions were classified independently in duplicate. A negative binomial regression analysis controlling for several confounding variables was performed to obtain regression coefficients; p values were obtained via likelihood ratio testing. RESULTS. A total of 995 primary studies were included. Fifty-one titles (5.1%) and 782 conclusions (78.6%) were positive or positive with qualifiers; 942 titles (94.7%) and 127 conclusions (12.8%) were neutral; and two titles (0.02%) and 86 conclusions (8.6%) were negative. Studies with positive, neutral, and negative titles were cited a mean of 0.66, 0.50, and 0.06 times per month. Studies with positive, neutral, and negative conclusions were cited a mean of 0.54, 0.42, and 0.34 times per month. Regression coefficients were 1.10 (95% CI, -0.08 to 2.20) and 0.91 (95% CI, -0.27 to 2.00) for positive and neutral titles, relative to negative titles. Regression coefficients were 0.19 (95% CI, 0.03-0.35) and 0.08 (95% CI, -0.12 to 0.27) for positive and neutral conclusions, relative to negative conclusions. Title and conclusion positivity demonstrated positive association with citation rate (p = 0.031 for both). CONCLUSION. Studies with positive titles or conclusions are cited more frequently in imaging diagnostic accuracy literature. This difference may contribute to overestimation of the accuracy of a test and, consequently, suboptimal patient outcomes.

Comparative reviews of diagnostic test accuracy in imaging research: evaluation of current practices.

PURPOSE: The purpose of this methodological review was to determine the extent to which comparative imaging systematic reviews of diagnostic test accuracy (DTA) use primary studies with comparative or non-comparative designs. METHODS: MEDLINE was used to identify DTA systematic reviews published in imaging journals between January 2000 and May 2018. INCLUSION CRITERIA: systematic reviews comparing at least two index tests (one of which was imaging-based); review characteristics were extracted. Study design and other characteristics of primary studies included in the systematic reviews were evaluated. RESULTS: One hundred three comparative imaging reviews were included; 11 (11%) included only comparative studies, 12 (11%) included only non-comparative primary studies, and 80 (78%) included both comparative and non-comparative primary studies. For reviews containing both comparative and non-comparative primary studies, the median proportion of non-comparative primary studies was 81% (IQR 57-90%). Of 92 reviews that included non-comparative primary studies, 86% did not recognize this as a limitation. Furthermore, among 4182 primary studies, 3438 (82%) were non-comparative and 744 (18%) were comparative in design. CONCLUSION: Most primary studies included in comparative imaging reviews are non-comparative in design and awareness of the risk of bias associated with this is low. This may lead to incorrect conclusions about the relative accuracy of diagnostic tests and be counter-productive for informing guidelines and funding decisions about imaging tests. KEY POINTS: • Few comparative accuracy imaging reviews include only primary studies with optimal comparative study designs. Among the rest, few recognize the risk of bias conferred from inclusion of primary studies with non-comparative designs. • The demand for accurate comparative accuracy data combined with minimal awareness of valid comparative study designs may lead to counter-productive research and inadequately supported clinical decisions for diagnostic tests. • Using comparative accuracy imaging reviews with a high risk of bias to inform guidelines and funding decisions may have detrimental impacts on patient care.