Investigation results

Question 1

Arthrocentesis - septic arthritis

Answer 1

Colour: grey or bloody

Clarity: Turbid

WCC: >50,000 (normal <200)
- remember partially treated or early infections may be intermediate

PMN: >85%

No crystals

bacteria may be seen, and grows on culture
surface antigens of H influenza and S pneumonia may be detected

Question 2

Arthrocentesis: crystal arthropathies

Answer 2

Colour: yellow to milky

Clarity: cloudy

WCC: 15-20,000

PMN: ~70% (usually >50%)

Crystals:
pseudo gout = calcium pyrophosphate (weak positive birefringence)
gout = urate (strong negative birefringence)

bacteria: none

Question 3

CSF - normal

Answer 3

pressure:
adults = 70-180 mmH20 or 5-20cmH20
young kids = 10-100 mmH20
8-16 years = 60-200mmH20

clear appearance

<4 lymphocytes
no neutrophils
no red cells

protein 0.15-0.45g/L (falsely elevated by blood)

glucose: proportional to blood glucose (usually 60-80% of venous sample collected at the time)

Question 4

CSF - viral

Answer 4

pressure: normal or mildly increased

clear appearance

<1000 WCC

<1g/L protein (essentially normal or slightly high)

glucose normal

less PMN than bacterial

Question 5

CSF - bacterial

Answer 5

pressure: high (>30cmH20)

turbid appearance

elevated protein (>1g/L)

low glucose (<2.2)

WCC elevated (>500)

90% PMN

gram stain 60-90% positive