Use of 3x2 tables with an intention to diagnose approach to assess clinical performance of diagnostic tests: meta-analytical evaluation of coronary CT angiography studies

OBJECTIVE: To determine whether a 3 × 2 table, using an intention to diagnose approach, is better than the "classic" 2 × 2 table at handling transparent reporting and non-evaluable results, when assessing the accuracy of a diagnostic test. DESIGN: Based on a systematic search for diagnostic accuracy studies of coronary computed tomography (CT) angiography, full texts of relevant studies were evaluated to determine whether they could calculate an alternative 3 × 2 table. To quantify an overall effect, we pooled diagnostic accuracy values according to a meta-analytical approach. DATA SOURCES: Medline (via PubMed), Embase (via Ovid), and ISI Web of Science electronic databases. ELIGIBILITY CRITERIA: Prospective English or German language studies comparing coronary CT with conventional coronary angiography in all patients and providing sufficient data for a patient level analysis. RESULTS: 120 studies (10,287 patients) were eligible. Studies varied greatly in their approaches to handling non-evaluable findings. We found 26 studies (including 2298 patients) that allowed us to calculate both 2 × 2 tables and 3 × 2 tables. Using a bivariate random effects model, we compared the 2 × 2 table with the 3 × 2 table, and found significant differences for pooled sensitivity (98.2 (95% confidence interval 96.7 to 99.1) v 92.7 (88.5 to 95.3)), area under the curve (0.99 (0.98 to 1.00) v 0.93 (0.91 to 0.95)), positive likelihood ratio (9.1 (6.2 to 13.3) v 4.4 (3.3 to 6.0)), and negative likelihood ratio (0.02 (0.01 to 0.04) v 0.09 (0.06 to 0.15); (P<0.05)). CONCLUSION: Parameters for diagnostic performance significantly decrease if non-evaluable results are included by a 3 × 2 table for analysis (intention to diagnose approach). This approach provides a more realistic picture of the clinical potential of diagnostic tests.