Title:
A systematic review and meta-analysis of the accuracy of diffusion-weighted MRI in the detection of malignant pulmonary nodules and masses.

Abstract:
To perform a meta-analysis to assess the diagnostic performance of the diffusion-weighted magnetic resonance imaging (DWI) technique in discrimination of benign and malignant pulmonary nodules or masses.
Data sources were studies published in PubMed, MEDLINE, EMBASE, Cochrane Library, and China National Knowledge Infrastructure databases from January 2001 to May 2013. Studies evaluating the diagnostic accuracy of DWI for benign/malignant discrimination of pulmonary nodules in English or Chinese language were considered for inclusion. Methodological quality was assessed by the quality assessment of diagnostic studies instrument. Sensitivities, specificities, predictive values, diagnostic odds ratios (DORs), and areas under the receiver operating characteristic curve (AUCs) were calculated. Potential threshold effect, heterogeneity, and publication bias were investigated. We also evaluated the clinical utility of DWI in diagnosis of lung lesions.
Seventeen studies comprising 855 malignant and 322 benign lesions were included in this meta-analysis. There was no significant threshold effect. Summary receiver operating characteristic curve showed that AUC was 0.909 (95% confidence interval [CI], 0.862-0.931). Pooled weighted estimates of sensitivity, specificity, positive likelihood ratio (PLR), and negative likelihood ratio (NLR) were 0.828 (95% CI, 0.801-0.853), 0.801 (95% CI, 0.753-0.843), 4.01 (95% CI, 2.78-5.80), and 0.20 (95% CI, 0.15-0.27), respectively. Heterogeneity was found to have stemmed primarily from study design (retrospective or prospective study). Subgroup analysis showed that diagnostic performance (sensitivity, 0.88; 95% CI, 0.82-0.92 and specificity, 0.89; 95% CI, 0.79-0.96) of retrospectively designed studies was significantly higher than that of prospectively designed studies. The Deeks' funnel plot indicated the absence of publication bias.
With respect to the accuracy and DOR, DWI is useful for differentiation between malignant and benign pulmonary nodules or masses. Diagnostic test accuracy is not the be-all and end-all of diagnostic testing. Concerning PLR and NLR, DWI may not help to alter posttest probability compared to pretest probability to sufficiently alter physician's decision making. Future analyses should be conducted in large-scale, high-quality trials to evaluate its clinical value and establish standards of DWI measurement, analysis, and cutoff values of diagnosis.