COMPLETE BLOOD COUNT (VOCAB & THOUGHTS)

LEUKOPENIA - is a lab value interpretation, where the WBC count is low (below 4.5K). The cause depends on the clinical scenario. It may be seen with chemotherapy, radiation or aplastic anemia. 

LEUKOCYTOSIS - is a lab value interpretation, where the WBC count is high (above 11K). In my opinion clinicians often put too much stock into this finding. I find it unspecific and insensitive. Mild elevations are due to infection, inflammation, exercise, coughing, vomiting, many medications and even stress. Note, VERY high leukocytosis (above 50K) is highly suggestive of leukemia. 

HYPERLEUKOCYTOSIS - is a lab value interpretation, where the WBC count is very high (above 50K). It is usually due to leukemia. The Leukocyte Alk Phos (LAP) is negative in leukemia. 

LEUKEMOID REACTION - Leukem- is referring to leukemia. -oid is referring to “looks like but isn’t.” This is hyperleukocytosis not due to leukemia. It is a reassuring term.  The LAP is positive in a leukemoid reaction. 

NEUTROPHILIC LEUKOCYTOSIS - is a lab value interpretation, where the WBC count is high (above 11K) and the Neutrophil count is high (***). It suggests infection, acute inflammation or steroids. Steroids accomplish this in an unusual manner. They don’t actually increase the number of WBCs in your body, they disrupt vessel adhesion, so neutrophils can no longer hang out on the vessel walls, but instead must enter the bloodstream. 

LEFT SHIFT - is a lab value interpretation, where the WBC is high, the Neutrophil count is high and the Neutrophil Band count is high. Seen in acute infections. The Bands are less effective than mature Neutrophils because they have less Fc receptors (which recognize immunoglobulin). CD16 is the marker for Bands.  

NEUTROPENIA is a lab value interpretation, where the Neutrophil count is low (below 1,500). Severe infections occur below 500. Neutropenia suggests chemotherapy, radiation, late-sepsis or aplastic anemia. Chemotherapy halts the cell cycle, and rapidly dividing WBCs can’t be made fast enough. Severe infections pull the neutrophils from the blood towards the infection.

EOSINOPHILIA is a lab value interpretation, where the Eosinophil count is high. It suggests allergies, invasive parasites or asthma. It is not elevated with protozoans (malaria, giardia, amoebas) or non-invasive parasites (adult ascariasis or pinworms which only live in the alimentary tract). Eosinophilia is also seen in Hodgkin's Lymphoma (Mixed-Cellularity subtype) and CML. 

EOSINOPENIA is a lab value interpretation, where the Eosinophil count is low. It suggests steroids or Cushings.

BASOPHILIA is a lab value interpretation, where the Basophil count is high. The only noteworthy cause is CML. 

LYMPHOCYTOSIS is a lab value interpretation, where the Lymphocyte count is high. It suggests viral infection, Mono and pertussis (which blocks Lymphocytes from leaving the blood to enter the tissues).

LYMPHOPENIA is a lab value interpretation, where the Lymphocyte count is low (below 1,500). It suggests HIV, steroids, radiation or autoimmune disease. Steroids induce apoptosis in lymphocytes. Lupus directly kills lymphocytes with Abs. Lymphocytes are very fragile in general, and they are specifically the most sensitive cell in the human body to radiation. T-cell Lymphopenia is due to DiGeorge Syndrome. 

MONOCYTOSIS is a lab value interpretation, where the Monocyte count is high. Suggests chronic inflammation or cancer. Low yield.

POLYCYTHEMIA is a lab value interpretation, where the RBC count is high (≥6). Physiologic Polycythemia occurs with tissue hypoxia (COPD, high altitude) and the subsequent rise in EPO.  Pathologic Polycythemia occurs with blood cancer (Polycythemia Vera) or ectopic EPO secretion (renal adenocarcinoma). 

REACTIVE POLYCYTHEMIA is essentially pseudo-Polycythemia, since RBC count is measured as a concentration, it rises when the patient is dehydrated.