Pleural effusion: glucose and amylase could help diagnose an exudate.

Clinical bottom line (level 4)

  1. Exudates occurred in roughly half of patients with pleural effusions.
  2. A pleural fluid glucose 6.0 mmol/l or less, or amylase 1000 U/l or more made an exudate more likely - a third of these exudates were due to pancreatitis.
Light and Ball: Journal of the American Medical Association 1973; 225 (3): 257-260
Expires October 2003

The study

Setting: university hospital, USA

176 patients (aged ?, ?% male) pleural effusions

?independent unblinded reference standard, applied in all patients from a consecutive ?appropriate spectrum.
Reference standard:
  • exudate if:
    • malignancy: malignant cells on cytology, pleural biopsy or autopsy
    • tuberculosis pleurisy: M. tuberculosis in pleural fluid or presence of granulomas on biopsy
    • pneumonia: acute febrile illness with purulent sputum pulmonary infiltrates
    • others: pancreatitis, collagen vascular disease, PE (diagnosed by arteriography) and trauma
Diagnostic test: pleural fluid:
  • glucose 6.0 mmol or less
  • amylase 1000 U/l or more

The evidence

pre-test probability of exudate: 49%, (95% CI: 41% to 57%)

diagnostic test exudate transudate or undiagnosed LR+
(95% CI)		 post-test probability LR-
(95% CI)		 post-test probability
glucose 6.0 mmol/l or less 52 11 5.0
(2.8 to 8.8) 		83% 0.31
(0.21 to 0.47) 		23%
amylase 1000 U/l or more 16 2 8.5
(2.0 to 35) 		89% 0.80
(0.70 to 0.91) 		43%
total 71 75

Comments

  1. Data was calculated from dot plots.
  2. All patients (5) with effusions due to pancreatitis had amylase levels > 1000. (LR + > 100 {95% CI: 3.5 to inf}).

Citation

  1. Light RW, and Ball WC: Glucose and amylase in pleural effusions. Journal of the American Medical Association 1973; 225 (3): 257-260
Search Terms: reference from Pleural effusion chapter in 'Quick Consult Manual to Evidence-based Medicine': publd. Lippincott-Raven, 1997
Contributor: Chris Ball and Clare Wotton, October 2000
Reviewer:

Clinical Question.
Patient pleural effusion
Intervention or Exposure glucose and amylase concentration
Outcome exudates