Abstract 054: The Use of Administrative Data and Natural Language Processing to Estimate the Incidence of Statin-related Rhabdomyolysis
Introduction: Despite the problem of misclassification, many studies of adverse drug reactions (ADRs) rely on administrative data rather than events validated by medical record review. Hypothesis: We evaluated the new ICD-9 code for rhabdomyolysis (728.88) and natural language processing (NLP) as methods to identify cases of statin-related rhabdomyolysis, and estimated the incidence with various statins and doses.
Methods: We conducted a population-based study of statin users in a health maintenance organization in Washington State from 2006-2010. Trained abstractors reviewed the medical records of selected statin users to identify cases of statin-related rhabdomyolysis and myopathy, defined as muscle injury with a peak creatine kinase level ≥ 10x and 5-10x the upper limit of normal, in the absence of other likely etiologies.
Results: The review of medical records for 361 statin users with an administrative code for rhabdomyolysis or related codes yielded 24 cases of statin-related rhabdomyolysis and 12 of myopathy. NLP methods identified another 5 cases of rhabdomyolysis and 6 of myopathy. The positive predictive value of the rhabdomyolysis ICD-9 code in statin users was only 7.5%. Incidence rates appear in the Table. The incidence rate ratio (IRR) of statin-related rhabdomyolysis for simvastatin compared with other statins was 2.61 (95% CI, 1.03-7.84), and the IRR for the 80mg dose of simvastatin compared with 20mg was 12.2 (95% CI, 3.6-52.3). In an analysis of administrative diagnostic data alone, the IRR for simvastatin compared with other statins was 1.03 (95% CI 0.80-1.34), and for 80 mg dose of simvastatin compared with 20 mg it was 1.77 (95% CI 1.05-2.88).
Conclusions: Use of the administrative diagnostic code for rhabdomyolysis was highly nonspecific for this ADR and resulted in weaker associations than methods that verified ADRs with medical record review. These findings raise questions about the use of administrative data alone in studies of other medication ADRs when those events have other possible etiologies.
|Cases||Incidence rates (95% CI)*|
|Statin||Person-years of exposure||Statin-related rhabdomyolysis||Statin-related myopathy||Statin-related rhabdomyolysis||Statin-related myopathy|
|Simvastatin||170,605||23||10||13.2 (8.6-20.2)||5.9 (2.8-10.8)|
|<20mg/day||21,832||0||0||0 (0-16.9)||0 (0-16.9)|
|20-39mg/day||75,082||4||2||5.3 (1.5-13.6)||2.7 (0.3-9.6)|
|40-79mg/day||56,703||8||4||14.1 (6.1-27.8)||7.1 (1.9-18.1)|
|≥80mg/day||16,876||11||4||64.8 (32.3-116.9)||23.6 (6.4-60.3)|
|Other statins||116,154||6||8||5.2 (1.9-11.2)||6.9 (3.0-13.6)|
|All statins||286,758||29||18||10.1 (7.8-14.5)||6.3 (3.7-9.9)|
↵* Cases per 100,000 person-years of statin use
- © 2012 by American Heart Association, Inc.