Thomson Reuters, 4301 Connecticut Ave, Washington, DC 20008, USA.
BMC Musculoskelet Disord. 2012 Jun 15;13:103. doi: 10.1186/1471-2474-13-103.
Idiopathic inflammatory myopathies (IIMs) are a rare group of autoimmune syndromes characterized by chronic muscle inflammation and muscle weakness with no known cause. Little is known about their incidence and prevalence. This study reports the incidence and prevalence of IIMs among commercially insured and Medicare and Medicaid enrolled populations in the US.
We retrospectively examined medical claims with an IIM diagnosis (ICD-9-CM 710.3 [dermatomyositis (DM)], 710.4 [polymyositis (PM)], 728.81[interstitial myositis]) in the MarketScan® databases to identify age- and gender-adjusted annual IIM incidence and prevalence for 2004-2008. Sensitivity analysis was performed for evidence of a specialist visit (rheumatologist/ neurologist/dermatologist), systemic corticosteroid or immunosuppressant use, or muscle biopsy.
We identified 2,990 incident patients between 2004 and 2008 (67% female, 17% Medicaid enrollees, 27% aged ≥65 years). Overall adjusted IIM incidence for 2004-2008 for commercial and Medicare supplemental groups combined were 4.27 cases (95% CI, 4.09-4.44) and for Medicaid, 5.23 (95% CI 4.74-5.72) per 100,000 person-years (py). Disease sub-type incidence rates per 100,000-py were 1.52 (95% CI 1.42-1.63) and 1.70 (1.42-1.97) for DM, 2.46 (2.33-2.59) and 3.53 (3.13-3.94) for PM, and 0.73 (0.66-0.81) and 0.78 (0.58-0.97) for interstitial myositis for the commercial/Medicare and Medicaid cohorts respectively. Annual incidence fluctuated over time with the base MarketScan populations. There were 7,155 prevalent patients, with annual prevalence ranging from 20.62 to 25.32 per 100,000 for commercial/Medicare (83% of prevalent cases) and from 15.35 to 32.74 for Medicaid.
We found higher IIM incidence than historically reported. Employer turnover, miscoding and misdiagnosing, care seeking behavior, and fluctuations in database membership over time can influence the results. Further studies are needed to confirm the incidence and prevalence of IIM.
特发性炎性肌病（IIM）是一组罕见的自身免疫性综合征，其特征为慢性肌肉炎症和肌肉无力，且病因不明。关于其发病率和患病率，人们知之甚少。本研究报告了美国商业保险和医疗保险参保人群中 IIM 的发病率和患病率。
我们对 MarketScan®数据库中的 IIM 诊断（ICD-9-CM 710.3[皮肌炎（DM）]、710.4[多发性肌炎（PM）]、728.81[间质性肌炎]）的医疗索赔进行了回顾性检查，以确定 2004-2008 年的年龄和性别调整后的 IIM 年发病率和患病率。进行了敏感性分析，以评估专科就诊（风湿病学家/神经病学家/皮肤科医生）、全身皮质类固醇或免疫抑制剂使用或肌肉活检的证据。
我们在 2004 年至 2008 年间发现了 2990 例新发病例（67%为女性，17%为 Medicaid 参保者，27%年龄≥65 岁）。商业和医疗保险补充组合并的 2004-2008 年整体调整后 IIM 发病率为每 100000 人年 4.27 例（95%CI，4.09-4.44），而 Medicaid 为每 100000 人年 5.23 例（95%CI，4.74-5.72）。每 100000 人年的疾病亚型发病率分别为 DM 为 1.52（95%CI，1.42-1.63）和 1.70（1.42-1.97），PM 为 2.46（2.33-2.59）和 3.53（3.13-3.94），间质性肌炎为 0.73（0.66-0.81）和 0.78（0.58-0.97），分别为商业/医疗保险和 Medicaid 队列。发病率随时间波动，基础 MarketScan 人群有所波动。有 7155 例现患患者，商业/医疗保险（83%的现患病例）的年患病率范围为每 100000 人 20.62-25.32，而 Medicaid 的年患病率范围为每 100000 人 15.35-32.74。
我们发现 IIM 的发病率高于历史报告。雇主更替、编码错误和误诊、寻求医疗服务的行为以及数据库成员随时间的波动都可能影响结果。需要进一步的研究来证实 IIM 的发病率和患病率。
