A Clinically Meaningful Interpretation of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) II and III Data

Rationale and Objectives: This study aimed to calculate the multiple-level likelihood ratios (LRs) and posttest probabilities for a positive, indeterminate, or negative test result for multidetector computed tomography pulmonary angiography (MDCTPA) +/- computed tomography venography (CTV) and magnetic resonance pulmonary angiography (MRPA) +/- magnetic resonance venography (MRV) for each clinical probability level (two-, three-, and four-level) for the nine most commonly used clinical prediction rules (CPRs) (Wells, Geneva, Miniati, and Charlotte). The study design is a review of observational studies with critical review of multiple cohort studies. The settings are acute care, emergency room care, and ambulatory care (inpatients and outpatients). Materials and Methods: Data were used to estimate pulmonary embolism (PE) pretest probability for each of the most commonly used CPRs at each probability level. Multiple-level LRs (positive, indeterminate, negative test) were generated and used to calculate posttest probabilities for MDCTPA, MDCTPA + CTV, MRPA, and MRPA + MRV from sensitivity and specificity results from Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) II and PIOPED III for each clinical probability level for each CPR. Nomograms were also created. Results: The LRs for a positive test result were higher for MRPA compared to MDCTPA without venography (76 vs 20) and with venography (42 vs 18). LRs for a negative test result were lower for MDCTPA compared to MRPA without venography (0.18 vs 0.22) and with venography (0.12 vs 0.15). In the three-level Wells score, the pretest clinical probability of PE for a low, moderate, and high clinical probability score is 5.7, 23, and 49. The posttest probability for an initially low clinical probability PE for a positive, indeterminate, and negative test result, respectively, for MDCTPA is 54, 5 and 1; for MDCTPA + CTV is 52, 2, and 0.7; for MRPA is 82, 6, and 1; and for MRPA + MRV is 72, 3, and 1; for an initially moderate clinical probability PE for MDCTPA is 86, 22, and 5; for MDCTPA + CTV is 85, 10, and 4; for MRPA is 96, 25, and 6; and for MRPA + MRV is 93, 14, and 4; and for an initially high clinical probability of PE for MDCTPA is 95, 47, and 15; for MDCTPA + CTV is 95, 27, and 10; for MRPA is 99, 52, and 17; and for MRPA + MRV is 98, 34, and 13. Conclusions: For a positive test result, LRs were considerably higher for MRPA compared to MDCTPA. However, both a positive MRPA and MDCTPA have LRs >10 and therefore can confirm the presence of PE. Performing venography reduced the LR for a positive and negative test for both MDCTPA and MRPA. The nomograms give posttest probabilities for a positive, indeterminate, or negative test result for MDCTPA and MRPA (with and without venography) for each clinical probability level for each of the CPR.