Synovial fluid analysis

WHAT TO PUT ON LAB FORM

  • – appearance
  • – WCC
  • – RBC
  • – microscopy + culture
  • – protein
  • – LDH
  • – glucose
  • – crystals

INTERPRETATION

Appearance

  • normally clear to light yellow

WCC

  • Suggests:
    -> infection
    -> gout
    -> pseudogout
    -> inflammatory arthritides (RA, seronegative)

RCC

  • Suggests:
    -> traumatic tap
    -> haemarthrosis (spontaneous or traumatic)

Protein

  • > 30g/L = exudate
    -> infection and inflammatory arthritides

LDH

  • >300IU/L
    -> RA
    -> gout
    -> infection

Glucose

  • < ½ serum
    -> infection
    -> severe inflammation

Crystals

  • Either:
    -> gout: monosodium urate, needle shaped
    -> pseudogout: calcium pyrophosphate dehydrate, birefringent, rhomboidal crystals

  • Crystals:
    • Calcium pyrophosphate (pseudogout)
      • Positive birefringence
      • Rhomboid shaped, Yellow crystals
    • Calcium urate (Gout)
      • Negative birefringence
      • Needle shaped crystals, Blue crystals
  • Gram stain
    • Positive in <25% gonococcal infections
    • Positive in 50-75% non-gonococcal

CCC 700 6

Critical Care

Compendium

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