This article is from the Interpretation Of Lab Test Profiles, by Ed Uthman email@example.com with numerous contributions by others.
The WBC is really a nonparameter, since it simply represents the
sum of the counts of granulocytes, lymphocytes, and monocytes
per unit volume of whole blood. Automated counters do not
distinguish bands from segs; however, it has been shown that if
all other hematologic parameters are within normal limits, such
a distinction is rarely important. Also, even in the best hands,
trying to reliably distinguish bands from segs under the
microscope is fraught with reproducibility problems. Discussion
concerning a patient's band count probably carries no more
scientific weight than a medieval theological argument.