Arthritis & Rheumatism, Volume 63,
November 2011 Abstract Supplement
Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Chicago, Illinois November 4-9, 2011.
International Classification of Diseases-Clinical Modification-9 Codes for the Diagnosis of Dermatomyositis and Polymyositis in Discharge Summaries: Evidence of Acceptable Validity.
Narang1, Neera, Fiorentino2, David, Krishnan3, Eswar, Chung4, Lorinda
Dermatomyositis (DM) and polymyositis (PM) are rare autoimmune diseases classically characterized by muscle inflammation. Epidemiologic studies using large administrative and hospitalization databases rely on the accuracy of the International Classification of Diseases-Clinical Modification-9 (ICD-CM-9) codes for case definitions. The purpose of this study is to evaluate the accuracy of ICD-CM-9 codes for DM and PM in hospital discharge summaries.
We identified all patients in the Stanford Hospital and Clinics database who had the ICD-CM-9 codes for DM (710.3) and PM (710.4) associated with any clinical encounters during the years 19962004. Of those, only patients who had hospital discharge summaries with any mention of these ICD-CM-9 codes were included in our study. We then performed a comprehensive medical record review of both inpatient and outpatient medical records to determine the proportion of patients who fulfilled accepted classification criteria for the diagnosis of DM and PM. Bohan and Peter criteria was used to classify patients as definite, probable, and possible DM or PM. Patients with clinically amyopathic DM were evaluated using the Sontheimer/Euwer criteria.
A total of 332 patients with the ICD-CM-9 codes 710.3 and 710.4 were identified in the Stanford Hospital and Clinics database. 42 of these patients had inpatient hospitalizations between 19962004. 30 patients had ICD-CM-9 code 710.3 (DM) and 12 had ICD-CM-9 code 710.4 (PM). Of the 30 patients with ICD-CM-9 code 710.3, 24 (80%) fulfilled Bohan and Peter criteria for DM (14 definite, 5 probable, 5 possible). Of these, 8 had muscle biopsies consistent with DM. 2 additional patients met Sontheimer/Euwer criteria for amyopathic DM. 1 of the 4 patients who did not fulfill criteria for DM actually met ACR criteria for systemic sclerosis. 10 of 12 (83%) patients with ICD-CM-9 code 710.4 met Bohan and Peter criteria for PM (0 definite, 4 probable, 6 possible), however, only 2 patients had muscle biopsies consistent with PM, and 1 of the "probable" patients had a biopsy more consistent with rhabdomyolysis. The 2 other patients with 710.4 coding actually had DM and inclusion body myositis as verified by muscle biopsy.
Our study suggests that ICD-CM-9 codes of 710.3 and 710.4 used for coding discharge summaries are >= 80% accurate in identifying cases of DM and PM, respectively, who fulfill currently accepted classification criteria for at least possible disease.
To cite this abstract, please use the following information:
Narang, Neera, Fiorentino, David, Krishnan, Eswar, Chung, Lorinda; International Classification of Diseases-Clinical Modification-9 Codes for the Diagnosis of Dermatomyositis and Polymyositis in Discharge Summaries: Evidence of Acceptable Validity. [abstract]. Arthritis Rheum 2011;63 Suppl 10 :244