Incidence and temporal trends of primary immunodeficiency: a population-based cohort study.

OBJECTIVE: To determine the incidence and temporal trends of primary immunodeficiency diseases (PIDs) and examine whether an association exists between delayed diagnosis and increased morbidity.

PATIENTS AND METHODS: We performed a historical cohort study to describe the epidemiology of PIDs in Olmsted County, Minnesota, during a 31-year period from January 1, 1976, through December 31, 2006, using the Rochester Epidemiology Project. Incidence and trends over time, presence of comorbid conditions, and trends in management were determined.

RESULTS: During the 31-year study period, 158 new cases of PIDs were diagnosed, with an overall incidence rate of 4.6 per 100,000 person-years. The rate of PIDs from 2001 through 2006 (10.3 per 100,000 person-years) was nearly 5 times higher than that from 1976 through 1980 (2.4 per 100,000 person-years). The associations between continuous variable(s) and categorical outcome(s) were assessed by using the Wilcoxon rank sum test. Longer delay in diagnosis was significantly associated with recurrent sinusitis (P<.001), recurrent pneumonia (P=.03), and subsequent treatment with immunoglobulins (P<.001). On the basis of Kaplan-Meier survival estimates, the proportion of patients surviving at 10 years after diagnosis was 93.5% (95% confidence interval, 85.9%-97.1%). However, older age at diagnosis was significantly associated with mortality (P=.01).

CONCLUSION: This is one of the first population-based studies to examine the temporal trends of PIDs. The incidence of PIDs increased markedly between 1976 and 2006. In this cohort, a delay in diagnosis was common and was associated with increased morbidity. Despite substantial morbidity, most patients with PIDs can expect a normal life span.