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Pleural Fluid

The British Thoracic Society (Hooper C, Lee YCG, Maskell N. Investigation of a unilateral pleural effusion in adults. Thorax 2010;    65: Supplement 2, ii4-ii17), recommends that   Light’s criteria are used for patients not receiving (or recently receiving) diuretics.  Serum and effusion total protein and LDH should be measured.  Fluid is an   exudate if   any of the following criteria are met:

  • Fluid:serum protein ratio >0.5
  • Fluid LDH >67% of the upper limit of normal for serum   (i.e. >166 U/L in our laboratory)
  • Fluid:serum LDH ratio >0.6

An alternative is to use the serum-effusion albumin gradient (  SEAG). Serum albumin and effusion albumin are measured and then the effusion albumin value is subtracted from the serum albumin value.

  • SEAG <12g/L is an exudate, 
  • SEAG >12g/L is a transudate

This has been found to be useful in classifying patients on diuretics or who have recently been on diuretics.

Ascitic fluid

Measure the fluid total protein:

  • Levels below 25-30 g/L classed as “transudates” (cirrhosis, CCF, nephrotic)
  • Levels above 25-30 g/L classed as “exudates” (inflammation or infection)

An alternative to the exudate-transudate concept is Serum Ascites Albumin Gradient (SAAG). Serum albumin and ascitic fluid albumin are measured.

  • SAAG = <11 g/L (low albumin gradient) associated with inflammation and infection
  • SAAG = > 11 g/L (high albumin gradient) associated with portal hypertension


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While contagious viruses are active year-round, winter is a prime time for norovirus, colds, influenza (flu), and other respiratory illnesses.


These infections are highly contagious, so we urge people to stay away unless their visit is absolutely essential to help reduce the spread of infection within our hospitals.

Hospitals are full of sick people, many of them frail and elderly, so bringing germs into a hospital is the worst thing you can do.  We have an active programme of infection prevention but we can’t spot visitors who really shouldn’t be here.  Please stay at home if you’re unwell to help aid the wellbeing and recovery of our patients.