This question was posed by a participant in the Rutgers University graduate course, CLSC 5123, Advanced Hematology. Rutgers' Clinical Laboratory Science program, directed by Elaine Keohane, PhD, offers an online masters degree program with advanced coursework that atrracts laboratory supervisors and managers. Here is the question.
My laboratory has had some requests recently to “identify schistocytes in the urine” that was positive for blood. They wanted to see if the RBCs in the urine were lysed on patients that had schistocytes called in their peripheral blood smear. We could not find any procedure that would help us in the identification process, nor did we think that it would be possible since we are only working on the high dry 40X field. I am not sure if schistocytes can be excreted in the urine, or if they would just show up as a positive blood on the dipstick and negative microscopically.
Here's Dr. Keohane's response:
I have not heard of a test for schistocytes in the urine and I am not aware of a clinical application for that. If there are schistocytes on the PB film, that means the RBCs were lysed within the vasculature, microangiopathic hemolysis. This is accompanied by decreased haptoglobin, increased LD, positive serum and urine hemoglobin; and no or few RBCs in urine sediment. If there are schistocytes in the PB, they would not normally pass through the glomerulus unless there was glomerular damage. Secondly, it would be very difficult to identify schistocytes in the urine sediment at 40X as you indicated. The concentration of solutes in the urine would affect the cells. Storage in hypotonic urine would cause hemolysis; a concentrated urine would cause crenation. What condition was suspected?
I'm wondering if our participants have had any experience with a request like this or can shed light on the purpose for detecting schistocytes in urine sediment.