The Diagnostic Power of 18F-FDG PET-CT Scanning for Discriminating Malignant From Non-malignant Causes in Unilateral Pleural Effusions

The investigators follow the STARD 2015 guideline for reporting diagnostic accuracy studies.

The investigators will review the hospital's administrative database of patients who underwent a thoracocentesis from January 2013 to January 2015. Patients at Department of Respiratory Medicine, Zealand University Hospital, Roskilde and Department of Respiratory Medicine, Naestved Hospital, Region Zealand, Denmark (two large respiratory centres with specialised functions) is eligible for inclusion. Patients are included irrespective of cytology and chemical analysis.

The investigators will review the patients' medical records and images retrospectively. To reduce the number of false negatives, the investigators complete a 1-year follow-up.

Patients older than 16 years are included, irrespective of smoking history and comorbidities, if both thoracocenteses, chest x-ray, a CT-scanning and a PET-CT scanning is performed. Exclusion criteria are previously diagnosed lung cancer, thoracic malignancy or incomplete data.

Classification of results The investigators chose the combination of investigations recommended by the internationally acknowledged BTS guideline, which is endorsed by the Danish Society of Respiratory Medicine. Thoracocentesis, chest x-ray, CT findings and PET-CT findings is categorized as either normal (i.e. not suggestive of any aetiology of the unilateral pleural effusion), suggestive of other lung pathology or suggestive of malignancy (i.e. representing a possible aetiology of the unilateral pleural effusion).