Ask the Lab Scientist Q4 2020

Questions submitted by readers and answered by the CLL Society Medical Advisory Board

By Susan Leclair, PhD, CLS (NCA)

1. Two questions from a newly diagnosed CLL 57-year-old male.

 A. Flow cytometry shows 98% of my B cells are CD19+. I assume this is kind of typical, to have almost all of your B cells be “bad?”

 B. My differential showed 7% neutrophil and 90% lymphocyte. Flow cytometry referenced a cell population of 44/48/6 lymphocytes/granulocytes/monocytes. Is this just because that is the ratio they sought to identify by the staining process, i.e., it has no relation to my actual WBC percentages?

Here is the answer from Dr. Susan Leclair, a laboratory scientist

Yes, the CD19 is part of the collection of antigens (usually called CD for clusters of differentiation) that is common in B-cell CLL. The most frequent combination is CD5, CD19, and CD20. There are others that are of interest as well.  The presence of CD 19 is not a strong indicator of anything bad as it should be present on normal maturing B cells. 

 The types of cells are quantified by different measures. The typical traditional method counts only 100 cells while one automated method counts 50,000 cells. The flow cytometry method used for the characterization of lymphocytes such as yours can go as high as 100,000 cells. As a consequence, it is not surprising to see different percentages.

 

2. I want to know if my LYMPHOCYTES 0.44 and MONOCYTES 0.07 is in normal range.

 Here is the answer from lab scientist, Dr. Susan Leclair

There are lots of important and highly variable ways to evaluate your values here. I am going to assume that these numbers are percentage values.  

The first and most correct answer is for you to look at the report form. In another column, usually to the right of your own results or just beneath each value) there will be a set of values in parentheses. These are the reference ranges that have been developed by the staff at the Laboratory facility you use. Technically speaking, you should use no other ranges as they reflect the method, the instrumentation, and the technique used at that facility.

The second answer is that, of course, since adult human white cell distribution does not vary all that much from one person to another, it is possible to give a general assessment without having the information about the Laboratory facility. The problem with these general “guesses” is it’s obviously at the far ends. One laboratory, for example, might say that their reference range for lymphocytes is .20 to .40 while another one in the same city might have a range that is .20 to .45. Your result of .44 might be acceptable in one Laboratory but not in another.

The third way is to look at the values at their most personal – that is to compare these values with prior values of your own. Reference ranges are generally thought of as guideposts not fixed truth. So, if in the last six months, your lymphocyte range has been in the .4 to .5 range then the interpretation is that nothing has changed in the last 6 months. 

One word of caution here is that percentage lymphocyte count is not as valuable as the absolute count. The absolute count (usually noted as ABS or #) is not subject to misinterpretation. In this part of the report, my guess is that you will see an absolute increase (greater than 5.0×10^9/L) in the number of lymphocytes as that is major criteria for the diagnosis of CLL. The lower this value, the better it is.

 

3. If the count of lymphocytes is 50%, is that good for the age of 15?

Here is the answer from lab scientist, Dr. Susan Leclair:

There is no answer to this without having the total white cell count because it is important to answer the question “50% of what.” 

There are two forms of differentials and most of time you should be looking at only one – the absolute or ABS or # count. That differential format tells you at one glance if there is any specific cell type which is increased or decreased.

Typically, the result in the upper half of the report is the percentage or % differential. This is the first type ever used and is limited to counting the first 100 cells seen in the evaluation of a blood smear.  The numbers are then reported out as a percentage. The strength of this format is that a trained scientist is not only identifying the cells but also evaluating the cells for quality. 

The weaknesses of this method are two-fold. Only 100 cells are evaluated so it is possible to miss rare cells and thus alter the values. The more important weakness is that this method must total 100 cells. So, it is difficult to impossible at times to determine if the percentages were caused by the increase in one cell line or the decrease in another. 

The second and newer method of identifying cells is by using an automated counter. A sample of cells (in some instruments as many as 50,000 cells) are counted one by one. The value then that is reported is the actual or absolute (ABS or #) number of cells counted. This method is crystal clear as to which cell is active change agent. Its main drawback is that you no longer have that trained scientist giving the cells a close evaluation.

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Susan Leclair, PhD, CLS (NCA) is Chancellor Projessor Emerita at the University of Massachusetts Dartmouth; Senior Scientist, at Forensic DNA Associates; and Moderator and Speaker, PatientPower.info – an electronic resource for patients and health care providers.