Incidence and prevalence of idiopathic inflammatory myopathies among commercially insured, Medicare supplemental insured, and Medicaid enrolled populations: an administrative claims analysis

Table 5 Annual myositis prevalence (2004–2008): Base case and sensitivity analysis

Year	Commercial and Medicare supplemental database (per 100,000 individuals)	Annual prevalence 95% CI	Medicaid database (per 100,000 individuals)	Annual prevalence 95% CI
Base case analysis
2004	22.96	21.92-24.01	15.35	14.20-16.50
2005	25.32	24.26-26.38	32.74	30.06-35.42
2006	22.99	22.04-23.94	29.56	26.49-32.64
2007	22.15	21.29-23.00	27.98	24.99-30.98
2008	20.62	19.83-21.41	24.42	21.68-27.15
Sensitivity analysis ¹
2004	19.43	18.47-20.39	12.39	11.36-13.42
2005	21.63	20.66-22.61	28.75	26.24-31.25
2006	19.71	18.82-20.59	23.98	21.21-26.75
2007	19.46	18.65-20.26	22.55	19.86-25.24
2008	18.47	17.72-19.22	19.15	16.73-21.57

¹Myositis patients with presence of muscle biopsy on or within one year before or after prevalence date; specialist visit on or within one year after the prevalence date; presence of immunosuppressants and/or systemic corticosteroids on or within one year after index date. Specialist included rheumatologist, dermatologist, or neurologist.

ISSN: 1471-2474