LAUSR

The International Classification of Disease (ICD) codes are used worldwide and are usually collected and comprised in administrative databases. These data are a valuable source of information for both inpatient and outpatient healthcare encounters. ICD-9 codes have been widely used in studies utilizing large national databases that evaluate the clinical epidemiology of encephalitis in the United States [1]. Many studies have showed that ICD-9 codes have different accuracy in other diseases [2–4]. To our knowledge, this is the first study in the United States to evaluate the diagnostic accuracy of ICD-9 codes in encephalitis. We conducted a retrospective study of all adults with an ICD-9 discharge diagnosis of encephalitis. The study was collected from 17 hospitals from the Memorial Hermann Health (MHH) System and Harris Health System (HHS) in the Greater Houston area between March of 2010 and July of 2015. Medical records were reviewed independently by two physicians and were determined to be accurately classified as encephalitis if they met the definition established by the international encephalitis consortium [5]. The UT Health Committee for the Protection of Human Subjects, the Memorial Hermann Hospital Research Review Committee, and the Harris Health Research Committee approved the study. A total of 1241 cases were identified with an ICD-9 discharge diagnosis code of encephalitis. 777 patients were collected from Memorial Hermann Health System (MHH) and 464 patients were collected from Harris Health System (HHS). After a detailed chart review, we found the most common cause identified was not having a central nervous system infection in 580 (46.6%) patients. A total of 326 of 580 (56.2%) were from MHH system and 254 (43.8) were from HHS. Sepsis due to non-CNS related infections was the most common example of misclassification. A total of 244 of 1,241 (19.6%) patients were correctly coded as having encephalitis with significant differences between both health systems (P < 0.001, see Table 1). A total of 110 (14.2%) were from MHH and 134 (28.8%) were from HHS. Other frequent causes of miscoding were: hospital acquired meningitis in 148 (11.9%), community-acquired bacterial meningitis in 101 (8.1%), aseptic meningitis in 72 (5.8%), fungal meningitis in 68 (5.4%), tuberculous meningitis in 25 (2.0%), and parasitic meningitis in 3 patients (0.2%) (Table 1).