58
10. Measurements with the Microscope
10.3 Differentiation of Gout / Pseudo Gout
The use of the lambda plate compensator is a
prerequisite for this test.
Assembly → p. 28.
Orienting the Lambda Plate Compensator
• Rotate the lambda plate compensator out of
the light path (fig. 67).
• Bring the lambda plate compensator and
analyzer into cross position until they reach
maximum darkness (polarization → p. 53).
• Fix the cross position thus determined with
the clamping screw at the side (67.2).
•Swing in the lambda plate again.
The following section explains the basic
procedure for gout/pseudo gout differentiation.
This test is made possible due to the negative
birefringence of urates and positive
birefringence of pyrophosphates. Both gout
(monosodium urate) and pseudo gout (calcium
pyrophosphate) crystals tend to be needle
shaped. However, many crystals may be broken
and/or irregular. To do the test, it is necessary to
find at least one intact crystal oriented north-
south (i.e., vertically) and one east-west
(horizontally) in the field of view.
Procedure
To insure the test is being done correctly, a slide
of known monosodium urate crystals should be
used initially.
• Use of a 40x objective is recommended.
•Swing the lambda plate out of the path of light
(fig. 67).
• Place the slide on the stage and bring the
crystals into sharp focus. The needle shaped
crystals will appear white regardless of
orientation.
•Swing in the lambda plate and put the
orientation handle (67.1) in its extreme left
position. Crystals with a long dimension in the
N/S direction should appear yellow, and the
E/W direction should appear blue (fig. 68).
Fig. 67 Lambda plate compensator swung out
1 Orientation handle
2 Clamping screw
S
SS
S
2
1
90°
To Next Page
Loading...
