Clinical significance of osmotic matrix errors in automated hematology: the frequency of hyperglycemic osmotic matrix errors producing spurious macrocytosis.

Sporadic examples of spurious macrocytosis due to hyperglycemic osmotic matrix effects have been reported. The present study defines the degree of macrocytosis expected under hyperglycemic normonatremic conditions using a Coulter S + II Isoton + System and its frequency in a large inpatient and outpatient population. No examples of spurious macrocytosis due to hyperglycemia were encountered in a sample comprising 28,471 complete blood counts, of which 564 had macrocytosis.