title: Does this patient have an exudative pleural effusion? The Rational Clinical Examination systematic review.
abstract: OBJECTIVE
  Thoracentesis is performed to identify the cause of a pleural effusion. Although generally safe, thoracentesis may be complicated by transient hypoxemia, bleeding, patient discomfort, reexpansion pulmonary edema, and pneumothorax.
  
  
  OBJECTIVE
  To identify the best means for differentiating between transudative and exudative effusions and also to identify thoracentesis techniques for minimizing the risk of complications by performing a systematic review the evidence.
  
  
  METHODS
  We searched The Cochrane Library, MEDLINE, and Embase from inception to February 2014 to identify relevant studies.
  
  
  METHODS
  We included randomized and observational studies of adult patients undergoing thoracentesis that examined diagnostic tests for differentiating exudates from transudates and evaluated thoracentesis techniques associated with a successful procedure with minimal complications.
  
  
  METHODS
  Two investigators independently appraised study quality and extracted data from studies of laboratory diagnosis of pleural effusion for calculation of likelihood ratios (LRs; n = 48 studies) and factors affecting adverse event rates (n = 37 studies).
  
  
  RESULTS
  The diagnosis of an exudate was most accurate if cholesterol in the pleural fluid was greater than 55 mg/dL (LR range, 7.1-250), lactate dehydrogenase (LDH) was greater than 200 U/L (LR, 18; 95% CI, 6.8-46), or the ratio of pleural fluid cholesterol to serum cholesterol was greater than 0.3 (LR, 14; 95% CI, 5.5-38). A diagnosis of exudate was less likely when all Light's criteria (a ratio of pleural fluid protein to serum protein >0.5, a ratio of pleural fluid LDH to serum LDH >0.6, or pleural fluid LDH >two-thirds the upper limit of normal for serum LDH) were absent (LR, 0.04; 95% CI, 0.02-0.11). The most common complication of thoracentesis was pneumothorax, which occurred in 6.0% of cases (95% CI, 4.0%-7.0%). Chest tube placement was required in 2.0% of procedures (95% CI, 0.99%-2.9%) in which a patient was determined to have radiographic evidence of a pneumothorax. With ultrasound, a radiologist's marking the needle insertion site was not associated with decreased pneumothorax events (skin marking vs no skin marking odds ratio [OR], 0.37; 95% CI, 0.08-1.7). Use of ultrasound by any experienced practitioner also was not associated with decreased pneumothorax events (OR, 0.55; 95% CI, 0.06-5.3).
  
  
  CONCLUSIONS
  Light's criteria, cholesterol and pleural fluid LDH levels, and the pleural fluid cholesterol-to-serum ratio are the most accurate diagnostic indicators for pleural exudates. Ultrasound skin marking by a radiologist or ultrasound-guided thoracentesis were not associated with a decrease in pneumothorax events.
authors.affiliation: Department of Medicine, University of Toronto, University Health Network, Toronto, Ontario, Canada.
authors.forename: M Elizabeth
authors.initials: ME
authors.lastname: Wilcox
authors.affiliation: Section of General Internal Medicine, Lakeridge Health Oshawa, Oshawa, Ontario, Canada.
authors.forename: Christopher A K Y
authors.initials: CA
authors.lastname: Chong
authors.affiliation: Division of Respirology, Department of Medicine, University Health Network, Toronto, Ontario, Canada.
authors.forename: Matthew B
authors.initials: MB
authors.lastname: Stanbrook
authors.affiliation: Li Ka Shing Knowledge Institute of St. Michael's Hospital, Toronto, Ontario, Canada.
authors.forename: Andrea C
authors.initials: AC
authors.lastname: Tricco
authors.affiliation: Division of Geriatrics, St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Camilla
authors.initials: C
authors.lastname: Wong
authors.affiliation: Li Ka Shing Knowledge Institute of St. Michael's Hospital, Toronto, Ontario, Canada5Division of Geriatrics, St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Sharon E
authors.initials: SE
authors.lastname: Straus
mesh_terms: D002784:Cholesterol / Q000032:analysis; D003937:Diagnosis, Differential; D005122:Exudates and Transudates / Q000737:chemistry; D006801:Humans; D010996:Pleural Effusion / Q000175:diagnosis*; D011030:Pneumothorax / Q000517:prevention & control*
chemical_list: D002784:Cholesterol