Concentrate living mfs by adding 2% saponin and centrifuge at 1000 rpm for 3-5 minutes in an ordinary clinical centrifuge. A 2nd centrifuge method as in QBC by B-D is to use a standard 75 mm heparinized microcapillary tube as used for hematocrit determination. This requires only a drop of blood. Mfs may be present just above the buffy coat.
Concentration techniques which kill the mfs are required to prepare them for measurement and morphologic examination. Measurements vary with the different methods of preparation. When fixed in 2 % formalin (modified Knott's method), they shrink a little.