Diagnostic accuracy of MRI compared to CTPA for Pulmonary Embolism : A meta analysis

BackgroundThis meta-analysis presents a comparison between Computed Tomography Pulmonary Angiography (CTPA) and Magnetic Resonance Angiography (MRA), to diagnose a pulmonary embolism. Computed tomography presents the advantage of imaging the entire thorax, facilitating the diagnosis of conditions that are commonly mistaken for pulmonary embolism, such as pneumonia, aortic dissection, and malignancy. UK and US guidelines have established CT amongst the basic investigations for pulmonary embolism. MRA does not require the use of ionizing radiation or iodinated contrast, thus making it possible for routine use of multiphasic acquisitions as well as for repeated contrast injections MethodologyFor the collection of the data, a search was done by two individuals using PubMed, Google Scholar, and Cochrane Library databases for all relevant literature. Full - Text Articles written only in English were considered. Each qualifying paper was independently evaluated by two reviewers. Each article was analyzed for the number of patients, their age, procedure modality, and incidence of the pre decided complications. ResultsThe results also showed a high positive predictive value of 0.947 or 94.7% for MRA in the diagnosis of Pulmonary embolism, as compared with CTPA. Some analyses have marked MRA to have low specificity. These results establish MRA as a respectable alternative for diagnosis of APE, especially in cases when reducing radiation exposure is desired. However, the gold standard of diagnosis remains Computed Tomography Pulmonary Angiography. ConclusionAs the results show, though MRA has high statistical value for the diagnosis of pulmonary embolism, it also has its drawbacks. MRA cannot be used in severely ill patients as it continues to be challenging, with the longer scan times and multiple breath holds that are required in different MR protocols are difficult to follow in these patients. CTPA remains the gold standard for diagnosis of Pulmonary embolism, with MRA as a secondary test used when CTPA is contraindicated.