Starting November 29th, 2022, Corewell Health West, Hematology Laboratories will begin reporting absolute counts for white blood cell (WBC) manual differentials, in addition to relative (percentage) counts. The WBC differential count determines the number of each type of white blood cell present in the blood. It can be expressed as a percentage or as an absolute value. Of these, the absolute value is much more important than the relative value, given that clinically relevant WBC elevations and declines are defined by their absolute numbers, not by their relative proportions, and there is potential for error if this conversion is performed outside the laboratory.
Based on this information it is recommended by the CAP Hematology and Clinical Microscopy Resource Committee that the absolute count should be the preferred reporting method for the WBC differential.
As part of this change in reporting, some differences will be noticeable
1. Bands will no longer be reported, as they will be included in the absolute neutrophil count (ANC).
2. Changes around absolute neutrophil count (ANC) reporting
a. If ANC is desired, CBC with differential needs to be ordered.
i. The ANC will be reported with the initial CBC results.
b. ANC will NOT be reported in CBCs without differential.
i. If a manual differential is added on to a CBC without differential, the ANC must be calculated from the percentage count.