Page 258 - Clinical Hematology Atlas

242 SECTION FIVE MISCELLANEOUS

A B
FIGURE 24–34A Calcium pyrophosphate crystals, FIGURE 24–34B Calcium pyrophosphate crystals,
polarized light microscopy (synovial fluid 31000). polarized with red compensator (synovial fluid
(Courtesy George Girgis, MT [ASCP], Indiana 31000). (Courtesy George Girgis, MT [ASCP],
University Health.) Indiana University Health.)

Note the orientation of the crystals and corresponding colors. Crystals appear blue when
parallel to the axis of slow vibration or yellow when perpendicular to the axis. Calcium
pyrophosphate is only weakly birefringent, so that the colors are not as bright as monosodium
urate crystals (see Figure 24-32).