This study provides an update on the incidence of chronic lymphocytic leukemia (CLL) and monoclonal B-cell lymphocytosis (MBL) in a major Canadian city using the 2008 World Health Organization (WHO) diagnostic criteria. Incidence calculations were performed using data from a centralized flow cytometry laboratory servicing southern Alberta, Canada. The age-standardized incidence of 4.01 cases of CLL per 100,000 person-years is nearly half the rate previously reported in Canada. Compared to previous criteria based on absolute lymphocyte count rather than absolute B-cell count, utilizing the 2008 WHO criteria resulted in a 47.6% decline in CLL incidence (8.42 cases per 100,000 using 1996 criteria). As a consequence, MBL rates are 64% higher. In contrast to 1996 criteria showing a peak CLL incidence between ages 70-74, age-specific incidence rates show a continuous increase with advancing age using the 2008 guidelines. We also report a higher male to female ratio of CLL than previous Canadian reports (1.80:1). CLL incidence in southern Alberta is lower than rates recently reported in the United States using the same criteria. This difference may be due in part to the low median age and the lower proportion of persons of Caucasian European ancestry present in our study population.
Keywords: Canada; Chronic lymphocytic leukemia; Epidemiology; Flow cytometry; Incidence; Monoclonal B-cell lymphocytosis.
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