CELL COUNTS

Question 1

Synovial Fluid

Answer 1

Synovial fluid

Normal

• clear / straw coloured
• quite viscous due to the presence of hyaluronidase
• WCC < 200/µL

Inflammatory

• turbid
• less viscous
• WCC 2,000 - 50,000/µL
• usually > 50% polymorphs

Infected

• opaque
• easily withdrawn
• WCC of > 50,000/µL
• > 85% polymorphs
• early or partially treated infections may have an intermediate WCC
• bacteria may be seen on and Gram stained fluid under microscopy
• surface antigens of H.influenzae and S.pneumoniae may also be detected
• bacteria grows on culture

Question 2

CSF

Answer 2

Question 3

Ascitic Fluid

Answer 3

ASCITIC FLUID

Serum:Ascitic Albumin Gradient (SAAG) = serum albumin – ascitic fluid albumin

> 11g/L = high SAAG = transudate

< 11g/L = low SAAG = exudate

Cell count and differential

> 250 neutrophils/mm3 = spontaneous bacterial peritonitis

> 250 WCC = spontaneous bacterial peritonitis

polymorphonuclear cells – bacterial

mononuclear cells – Tb or fungal

Gram stain and culture

monomicrobial = SBP

polymicrobial = secondary bacterial peritonitis -> search for perforated viscus

LDH

< 225U/L = transudate

> 225U/L = exudate

Glucose

normal in SBP

low in secondary bacterial peritonitis

Amylase

increased in pancreatic ascites

pH

< 7.0 suggests bacterial infection

Triglyceride

increased in chylous ascites

Cytology

malignant cells

Question 4

Diagnostic Peritoneal Lavage

Answer 4

Positive

•frank blood on free aspiration

• > 20 mL in adults
• > 10 mL in children

•RBC/mL

• > 100,000 mL in blunt injury
• > 5,000 RBCs/mL in penetrating injury
• > 500 WBC/mL (if obtained < 3hrs after the injury)
• bile (by inspection or chemical determination of bilirubin content)
• food particles (microscopic analysis of strained or spun specimen)

Intermediate

• pink fluid on free aspiration
• 50,000 - 100,000 RBCs/mL in blunt trauma
• 100 - 500 WBC/mL

Negative

• clear aspirate
• < 100 WBC/mL

Question 5

Pleural Fluid

Answer 5

Pleural fluid laboratory findings

Lights criteria (High protein and LDH = exudate), determines presence of exudate with protein and LDH levels

Pleural fluid protein to serum protein ratio >0.5

Pleural fluid LDH to serum LDH ratio >0.6

Pleural fluid level >2/3 of upper value for serum LDH

Additional criteria – Confirm exudate if results equivocal

Serum albumin – pleural fluid albumin <1.2g/dL

Exudate (local disease) (High protein). Local factors influence the accumulation or clearance of fluid.

Malignancy – Lung, breast, pleural.

Infection – Pneumonia, empyema, pleuritis, viral disease

Autoimmune – Rheumatoid, SLE

Vascular – PTE

Cardiac – Pericarditis, CABG

Respiratory – Haemothorax, Chylothorax

Abdominal – Subphrenic abscess

Transudate (systemic illness) (Low protein <30g). Imbalance between oncotic and hydrostatic pressures

Cardiac – CCF, PTE

Liver – Ascites, Cirrhosis

Renal – Glomerulonephritis, Nephrotic syndrome

Ovarian – Meigs syndrome

Autoimmune – Sarcoid

Thyroid – Myxoedema