Computed tomography of the chest in unilateral pleural effusions: outcome of the British Thoracic Society guideline.

Background: The guidelines from the British Thoracic Society (BTS) regarding the investigation of unilateral pleural effusions recommend computed tomography (CT) in exudates. We decided to investigate if clinicians follow BTS guidelines' recommendations with respect to CT in patients with unilateral pleural effusions. Secondly, to investigate the diagnostic consequences of following and not following this recommendation.

Methods: The study was a retrospective, non-randomized study including consecutive patients referred to our tertiary centers in 2013-2016 because of unilateral pleural effusion. Patients undergoing chest CT for unilateral pleural effusion of unknown cause after thoracentesis and chest X-ray were included. Patients were categorized as having pleural exudates or transudates, according to Light's criteria, if applicable. We registered use of CT, and calculated diagnostic values.

Results: In total, 323 of the 465 included patients underwent CT (69%). CT was performed in the majority of patients not having an exudate (transudates: n=40; 54%; Light's criteria not assessed: n=111; 67%). F-FDG positron emission tomography (PET)/CT without prior CT was performed in 32 patients with an exudate (58%). The sensitivity of a non-guideline supported CT (70%) was significantly higher compared to a guideline supported CT (47%), P value <0.045. The post-test probability of a positive guideline-supported CT [likelihood ratio (LR) positive 3.26] for a later diagnosis of thoracic malignancy increased the probability from 25% to 52%. A negative CT (LR negative 0.62) decreased the probability to 17%. For a non-guideline-supported CT the numbers were (LR positive 3.42) 53% and (LR negative 0.38) 11%, respectively.

Conclusions: Clinicians appear not to follow BTS guidelines when deciding to perform chest CT. The relevance of this deviation is supported by the superior sensitivity of CT non-guideline supported CT. Overall, CT is associated with suboptimal sensitivity and negative predictive values for the diagnosis of thoracic malignancy.