OBJECTIVE: To estimate the incidence of Churg-Strauss syndrome (CSS) among a large population of asthma drug users. METHODS: A retrospective study was conducted among patients who had been dispensed asthma drugs at 3 managed care organizations. Adults who received >or =3 dispensings of an asthma drug during any consecutive 12-month period between January 1, 1995 and June 30, 2000 were identified. Information on patient age, gender, enrollment status, asthma drugs dispensed, and inpatient and outpatient diagnoses and procedures was obtained from automated databases. Chart reviews were performed on persons identified by combinations of diagnostic and billing codes indicative of CSS. A rheumatologist reviewed abstracted information on all subjects; those who met >or =2 American College of Rheumatology criteria for CSS were reviewed by 2 clinical experts. Each clinical expert independently rated the cases; disagreements were resolved by consensus. Cases classified as having "probable/definite" CSS were included in these analyses. The incidence of CSS was estimated overall and according to patient gender, age, and calendar year. RESULTS: From a population of 184,667 asthma drug users contributing 606,184 person-years of exposure, 21 incident cases of CSS were identified (overall incidence of 34.6 per million person-years; 95% confidence interval 21.4 to 53.0). Incidence rates did not differ by gender and age group. The incidence rates for 1995, 1996, 1997, 1998, 1999, and the first 6 months of 2000 were 0, 22, 52, 75, 14, and 14 per million person-years respectively. CONCLUSIONS: Results from this population-based study suggest a somewhat lower incidence of CSS in asthma drug users than previously reported and provides important information as to the risk of developing CSS from a population-based perspective.

PURPOSE: Our aim was to identify individuals with Churg-Strauss syndrome (CSS) among asthma drug users, based on patterns of diagnostic and procedural codes (termed 'algorithms') contained in automated claims data. METHODS: A retrospective study was conducted among patients who had been dispensed asthma drugs at three HMOs. Individuals who received > or =3 dispensings of an asthma drug during any consecutive 12-month period beginning 1 January 1994 through 20 June 2000 were identified. Information on patient age, gender, enrollment status, asthma drugs dispensed, inpatient and outpatient diagnoses and procedures were obtained from the HMO automated databases. Twelve combinations of diagnostic and billing codes ('algorithms') were developed using the claims data to identify potential cases of CSS. Chart reviews blinded to drug exposure were performed using a standardized abstraction form. A rheumatologist reviewed abstracted information on all subjects, and those who met two or more American College of Rheumatology (ACR) criteria for CSS were further reviewed by two clinical experts. Cases were classified as unlikely, possible, or probable/definite CSS. Each clinical expert independently rated the cases; disagreements were resolved by consensus. RESULTS: A total of 185 604 patients who had been dispensed asthma drugs were identified. Three hundred fifty subjects were selected for chart review, and 15 were classified as having 'probable/definite' CSS. The algorithms that were most successful in identifying patients with CSS were as follows: (1) two or more codes for vasculitis (13 confirmed cases from 129 reviewed; positive predictive value 10%); (2) codes for both vasculitis and neurologic symptoms (6 confirmed cases from 15 reviewed; positive predictive value 40%) and (3) codes for both eosinophilia and vasculitis (4 confirmed cases from 5 reviewed; positive predictive value 80%). CONCLUSION: Automated claims data can be used to identify patients with CSS. This approach can facilitate better epidemiologic study of the risk factors for the condition.