Skip to Main Content

Uses

To determine the presence of uric acid crystals (in patients with gout) or calcium pyrophosphate crystals (in patients with pseudogout) in joint fluid.

Materials

Freshly collected joint fluid, glass microscope slide, coverslip, and polarizer.

FIGURE 25.6A

Polarized Uric Acid Crystals (×500). Intracellular needle-like uric acid crystals are seen within the polymorphonuclear cells from the joint fluid in a patient with gout, using a direct polarizing light. (Reproduced with permission, from Strasinger SK, Di Lorenzo MS. Urinalysis and Body Fluids. 5th ed. Philadelphia, PA: F.A. Davis Company; 2008, p. 216.)

FIGURE 25.6B

Compensated Polarized Uric Acid Crystals (×500). Once crystals are found with a direct polarizing light, identification is made by using a compensated polarized light. The yellow crystal is aligned parallel to the slow vibration component of the compensator (negatively birefringent). The blue crystal is perpendicular (crossed urate blue). (Reproduced with permission, from Strasinger SK, Di Lorenzo MS. Urinalysis and Body Fluids. 5th ed. Philadelphia, PA: F.A. Davis Company; 2008, p. 217.)

FIGURE 25.7A

Polarized Calcium Pyrophosphate Crystals (×1000). Intracellular rhomboid crystals in the joint of a patient with pseudogout. They may also appear as rods. (Reproduced with permission, from Strasinger SK, Di Lorenzo MS. Urinalysis and Body Fluids. 5th ed. Philadelphia, PA: F.A. Davis Company; 2008, p. 216.)

FIGURE 25.7B

Compensated Polarized Calcium Pyrophosphate Crystals (×1000). The blue calcium pyrophosphate crystal is aligned parallel to the slow vibration component of the compensator (positively birefringent). (Reproduced with permission, from Strasinger SK, Di Lorenzo MS. Urinalysis and Body Fluids. 5th ed. Philadelphia, PA: F.A. Davis Company; 2008, p. 217.)

Method

  1. To prevent interference from polarizing artifacts, clean the slide and coverslip with alcohol prior to using them.

  2. Using freshly collected unspun joint fluid, place a drop of joint fluid on the glass microscope slide.

  3. Overlay coverslip.

  4. View the slide using the polarizer.

  5. Scan at ×10 power; ×100 power is needed to see intracellular crystals.

FIGURE 25.8

Uncompensated Polarized Uric Acid Crystals (×400). The needle-like crystals can sometimes appear similar to those of calcium pyrophosphate dihydrate (CPPD) in pseudogout if not viewed under compensated polarized light. (Photo contributor: Jennifer Knight, MD.)

FIGURE 25.9

Compensated Polarized Uric Acid Crystals (×400). The needle-like crystals are negatively birefringent (yellow when parallel to the axis of the slow ray and blue when perpendicular), unlike CPPD, which is positively birefringent. (Photo contributor: Jennifer Knight, MD.)

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.