title: Most severe neutropenia in individuals with no chronic condition did not result in a specific diagnosis.
abstract: OBJECTIVE
  This study estimated the incidence of unexplained severe neutropenia (neutrophil count 500 x 10(6)/L) and hospitalized morbidity in the year after a finding of severe neutropenia in persons 2 years of age or older based on clinical laboratory data.
  
  
  METHODS
  Computer-stored data from the Kaiser Permanente Laboratory Management System/Results Management System were used to identify findings of severe neutropenia in members of Kaiser Permanente Southern California 2 years of age or older during the period January 1, 1997, through December 31, 1999. Computer record linkage and medical record review were used to exclude individuals with chronic disease or treatments with bone marrow toxic drugs known to cause neutropenia.
  
  
  RESULTS
  The incidence of findings of severe neutropenia was 47 per million persons per year (95% CI=42-53). Only 11% of individuals with a finding of severe neutropenia were hospitalized with neutropenia diagnosis. The hospitalization rate for infection occurring within 1 year of severe neutropenia was 3.2% (95% CI=1.5-6.2%).
  
  
  CONCLUSIONS
  Most laboratory findings of severe neutropenia in individuals with no chronic condition do not result in a specific diagnosis. In a population-based sample of findings of severe neutropenia identified by laboratory testing, hospitalization for infection was rare.
authors.affiliation: Kaiser Permanente Medical Care Program, Southern California, 393 East Walnut Street, Pasadena, CA 91188, USA. diana.b.petitti@kp.org
authors.forename: Diana B
authors.initials: DB
authors.lastname: Petitti
authors.forename: Richard
authors.initials: R
authors.lastname: Contreras
authors.forename: Michael
authors.initials: M
authors.lastname: Glowalla
authors.forename: Robert
authors.initials: R
authors.lastname: Miday
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000009:adverse effects; D000925:Anticoagulants / Q000009:adverse effects; D000927:Anticonvulsants / Q000009:adverse effects; D013956:Antithyroid Agents / Q000009:adverse effects; D002140:California / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D016001:Confidence Intervals; D003627:Data Interpretation, Statistical; D005260:Female; D006760:Hospitalization; D006801:Humans; D015994:Incidence; D007958:Leukocyte Count; D008297:Male; D008498:Medical Record Linkage; D008499:Medical Records; D008875:Middle Aged; D009503:Neutropenia / Q000453:epidemiology / Q000209:etiology*
chemical_list: D000900:Anti-Bacterial Agents; D000925:Anticoagulants; D000927:Anticonvulsants; D013956:Antithyroid Agents