While automated hematology analyzers provide reliable results in normal patients, they may not perform as well in ill patients. Certain findings require technologist review of the peripheral blood smear. The pathologist (or other reference person) should review the smear if unusual, unexpected or potentially significant findings are seen by the technologist.

NOTE: These are some indications for smear review. Some (presence of blasts) are universally accepted, while others may or may not be used based on local practices.


White blood cell findings:

(1) neutrophilia (> 20,000 per µL)

(2) neutropenia (< 1,500 per µL)

(3) lymphocytosis (> 10,000 per µL)

(4) monocytosis (> 2,000 per µL)

(5) eosinophilia (> 1,000 per µL)

(6) basophilia (> 1,000 per µL)

(7) atypical lymphocytosis (> 5% of differential count; since this may be easily triggered with leukopenia, it may be necessary to also specify a WBC count)

(8) leukemic or lymphoma cells present

(9) atypical myeloid cells

(10) apparent hiatus in granulocytic development (promyelocytes without myelocytes or metamyelocytes)


Red blood cell findings:

(1) sickle forms

(2) abnormal morphology

(3) microcytosis (low MCV)

(4) macrocytosis (high MCV)

(5) nucleated red blood cells

(6) elevated MCHC

(7) increased polychromasia (increased reticulocyte count)

(8) schistocytosis


Platelet findings:

(1) unexplained thrombocytopenia (platelet count < 50,000 per µL)

(2) thrombocytosis (platelet count > 1,000,000 per µL)



(1) suspicion of parasitic or bacterial forms in the smear

(2) any uncertainty in findings

(3) clinician request

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