Looking at blood smears is always a little tricky. First, this is one of the few situations in which you may actually need to use  your oil immersion lens. Please be careful. It's easy to run it through a slide. Knowing where to look on the slide can make all the difference between being able to see what's there, and simply being frustrated. You want to be way out on what we call the "feathered edge" of the slide. That is, you want to be almost off the shallow end of the blood smear, not in the middle of the slide. In most cases, the label is at the thick end of the slide, so head as far as you can in the other direction. You want to be right out where the little pointy ends of the blood smear disappear into nothing. You need to find an area where the RBC's just barely touch each other, or are free swimming. If you are looking at an area where the RBC's are piled on top of one another and the WBC's are dark and small, keep going to the thinner end of the slide.

When you study a smear, remember there are three formed elements to assess, as well as what can be learned from the background. No matter what you have been told about the condition the slide represents, always look at the RBC's, WBC's and platelets. The degree of blue staining in the background can also give you an indication of the amount of protein in the blood. The darker blue the background, the more there is. But again, be sure you are looking in the far reaches of the feathered end of the slide. These are real live clinical specimens. Good luck.
 
 

Slide B1, yeast in white blood cells.	Slide, B2 chronic lymphocytic leukemia.	Slide B3, chronic myelogenous leukemia.	Blood smear B4, mononucleosis.
Slide B5, hairy cell leukemia.	Slide B6, spherocytosis.	Slide B7, hemolytic anemia.	Slide B8, dimorphic red blood cell population.
		I'd like to take the quiz now.
Slide B9, chronic myelogenous leukemia in blast crisis.	Slide B10, Acute lymphocytic leukemia.

Mark Braun, MD braunm@indiana.edu
Copyright 1998, the Trustees of Indiana University