What is a left shift?

A left shift refers to the relative increase in immature forms of blood cells. The term actually comes from the fact that, if you go back to a patho book and look at the entire cascade diagram of how blood cells mature, the immature cells are on the left side of the old, standard diagram.

So, left shift typically means there are more band cells (% bands) in a CBC with differential. I personally think of bands as baby white cells. If the body is producing and mobilizing a large number of new white cells, then the body is attempting to fight off a very active infection. Normally, we only have 2-6% of our white cells as bands. If that percentage increases, then the infection is such that the body feels it's necessary to kick the baby white cells out of the nest before their time in order to join in the fight.

Hope that makes sense!

A left shift is an increase in the number of immmature neutrophils or polymorphonuclear leukocytes (PMN's). These are called band or stab neutrophils, and in more severe cases there may be metamyelocytes or myelocytes present. Mature (normal) neutrophils are referred to as segmented neutrophils or segs. In a normal differential there should be 0-6 bands per 100 WBC's and no metamyelocytes or myelocytes.

These immature cells make it into the bloodstream because chemical signals (cytokines, complement, etc.) released from the site of inflammation stimulate the bone marrow to release them prematurely. They continue to mature after entering the bloodstream, and the left shift will usually disappear within a few days if the cause of the inflammation is addressed.

An increased neutrophil count with a left shift is typically associated with bacterial infection, and may be increased in other inflammatory conditions or post-surgically.

I hope that I explained this well. Please let me know if you have any more questions. :)

Just a little more information....It was called a shift to the left because back in the Ole' days the CBC lab slips were short and wide. The immature cell counts were on the "left" of the lab report and so if the increase in immature cells occurred, there was a shift from the mature cell count on the right of the lab report to the left

thanks pjmommy for clarifying the left shift thing. i was wondering about it myself.

Has anyone ever seen one on a lab report? What does it look like? Does the lab report say "left shift" or do you have to note a certain difference in neutrophil counts? Thanks in advance, Stacey McCall/LPN/RN student nurse

I saw one today on a lab report in ICU. I had only heard about in on my med surge Oncology Rotation. It was explained to me that not only could it mean infection but could also mean a transition to certain types of cancer. I will explain what I saw on labs but don't hold me to exact numbers as this was at the end of my over night shift (12 hour shift 7p-7a) and I did 4 shifts in five days plus I work a full time job and I am in my last semester as a SN. LoL!

They showed the normal % ranges on left of page bands where 1%-3% and underneath them segs where 30%-40%. Then across the page where the results and this pt had bands in the 70 percentile range and segs wehere at 9%. This was a good example of a huge shift to the left. The term had originally been coined by where the stats where positioned on the lab reports and how suddenly the WBC would shift to the left which happen to be the segs side.

My patient had a rect temp of 104.5 so infection was a good possibility. He had O.D. issues as well. Recently found a mass in his spine. Not really sure what caused this shift to the left however lab also asked for a redraw from same pt.

:)

PJMommy said:

A left shift refers to the relative increase in immature forms of blood cells. The term actually comes from the fact that, if you go back to a patho book and look at the entire cascade diagram of how blood cells mature, the immature cells are on the left side of the old, standard diagram.

So, left shift typically means there are more band cells (% bands) in a CBC with differential. I personally think of bands as baby white cells. If the body is producing and mobilizing a large number of new white cells, then the body is attempting to fight off a very active infection. Normally, we only have 2-6% of our white cells as bands. If that percentage increases, then the infection is such that the body feels it's necessary to kick the baby white cells out of the nest before their time in order to join in the fight.

Hope that makes sense!

Love your explanation! I never thought of band = baby. That will stick me forever now! Thank you PJ!!!

Thank you for that explaination Muskylounge!

Another "left shift" is the oxy-hemoglobin dissassociation curve. This is truly reflected in a 'bell curve' type graph. Shifts reflect the ease in which RBCs release O2.

Guess we need some a bit more context here.

thanks, these comments are all super helpful! Sometimes I notice the physicians document a left shift and the Bands are not elevated so I wasn't sure if I had it right!

The hospital where I work now refers to it in terms of an I:T ratio (something that was new to me).