Incidence of peripheral blood eosinophilia and the threshold eosinophile count for indicating hypereosinophilia-associated diseases.

BACKGROUND: A definite threshold of the peripheral blood eosinophile count that indicates the presence of hypereosinophilia-associated diseases has not yet been determined.
METHODS: The threshold eosinophile count at which cases of hypereosinophilia-associated diseases (n = 25) can be differentiated from those of bronchial asthma (n = 101) was determined. Then, the incidences of eosinophile counts greater than 1.0 x 10(9)/l or the threshold level, were studied by analysis of 43,805 samples sent to the laboratory, and the diseases associated with the increased counts were determined.
RESULTS: The eosinophile count in cases of hypereosinophilia-associated diseases and in those of bronchial asthma were 10.967 +/- 1.680 x 10(9)/l and 0.574 +/- 0.045 x 10(9)/l, respectively (P < 0.001); the threshold was 2.052 x 10(9)/l. The percentages of samples with an eosinophile count of more than 1.0 x 10(9)/l and 2.052 x 10(9)/l were 0.6% and 0.1%, respectively; the latter comprised of 41 samples from 24 patients including eight with hypereosinophilia-associated diseases. The patients with hypereosinophilia-associated diseases had a significantly higher count, and a higher incidence of counts of more than 2.052 x 10(9)/l, than others, including patients with malignancies and symptoms conventionally referred as "atopic diseases".
CONCLUSION: Hypereosinophilia-associated diseases are associated with a very high eosinophile count of more than 2.052 x 10(9)/l, which was observed rarely.