This is taken from a CAP competency this year. I find it interesting that they seem to imply that vortexing the sample may be a valid tool. http://ocatp.medialabinc.net/courses/s_page.aspx?step=9&cassignment=5675288&cassignmenthash=a2b90633421f09dcb7634dffe9a3826d&oid=4701443&o=fb5102c0cdd8152617c4f01af58eccf9 2014 Pro Course: White Blood Cells Identify non-white blood cell particles that may interfere with automated white blood cell counts and interpret general instrument flagging messages. Particle Interference: Platelet Clumping In many laboratories, platelet clumps are a more common interference with accurate WBC counting than NRBCs or lyse-resistant RBCs. Image 1 shows clumps of platelets in a peripheral smear. Platelet clumps in peripheral blood samples are most often due to preanalytic errors, such as inadequate or delayed mixing of the sample after collection. Platelet clumping can also occur in patients with antibodies that can bind to platelets and are activated by EDTA. Image 1 Individual platelets normally shrivel and disappear when exposed to the lysing reagents used to obtain automated WBC counts. However, when clumps of platelets are present, the lyse used may not be strong enough to shrink these clumps to a size that will not interfere with the WBC count. This is especially true if the instrument uses a "soft" lyse. Analyzers that use a "hard" lyse to determine the WBC count are less likely to have inaccurate WBC results due to platelet clumps. In extreme cases, the platelet clumps may be large enough that they appear at or beyond the feather edge, rather than in the body of the smear. The feather edge of the smear should always be examined when platelet clumps are suspected, i.e., WBC interference or an unexpected low platelet count. Image 2 shows numerous large clumps at the very edge of the smear. Image 2 It is not always possible to distinguish WBC count interference caused by platelet clumps from that caused by lyse-resistant RBCs or NRBCs, as all three may appear at or near the same area on scattergrams and histograms. It is imperative to understand and correctly interpret histogram and scattergram displays on the analyzer in use. Platelet clumps can often be dispersed by vortexing the sample for 30-60 seconds and quickly reanalyzing. However, if interference is still evident, an alternate method must be used to obtain an accurate WBC count, such as collecting a new sample with a tube containing sodium citrate anticoagulant. Continue to the next page »