OBJECTIVES - To distinguish chronic idiopathic neutrophilia (CIN) in a cost-effective manner from neutrophilia caused by important underlying illnesses.
METHODS - This was a retrospective review of patients visiting a Veterans Affairs Medical Center over the last 10 years with a diagnosis of leukocytosis or myeloproliferative disorder. Of this group, fifty-seven patients from 1999 to 2008 were identified with CIN. Clinical and laboratory parameters were examined to identify CIN and establish its course. Eighty-one patients who presented from 2005 to 2010 with myeloproliferative disorders were also studied at time of diagnosis to determine any possible confusion with CIN.
RESULTS - The patients with CIN were followed for a mean of ≥ 7.3 years without progression to other serious disorders. Compared to non-CIN patients evaluated for neutrophilia, in multiple logistic regression analyses, smoking (P = .001) and increased BMI (P = .004) were significantly associated with CIN. No CIN patient developed a clinically apparent myeloproliferative disorder other than chronic myeloid leukemia (CML). Of the patients with myeloproliferative neoplasms reviewed at the time of their initial diagnosis, only CML occasionally presented with a picture consistent with CIN. For nonsmokers, the BMI of CIN patients was significantly higher than the average VA population (P < .001).
CONCLUSION - Cigarette smoking and obesity are confirmed as factors associated with CIN and may be causative. CIN is unlikely to develop into a clinically recognizable myeloproliferative neoplasm other than CML. Cost-effective guidelines for the diagnostic evaluation of neutrophilia in otherwise healthy patients are presented.