Validation of ICD-10 codes for identifying cases of chlamydia and gonorrhea

Abstract Background Public health researchers seek to use administrative health data captured in digital health systems to examine outcomes for individuals with sexually transmitted infections (STIs). Yet the International Classification of Diseases, Tenth Revision (ICD-10) codes used to identify cases of chlamydia and gonorrhea have not been validated. Objective We sought to assess the validity of using ICD-10 codes to identify cases of chlamydia and gonorrhea. Methods We utilized data from electronic health records gathered from private and public health systems from 1 October, 2015 to 31 December, 2016. Patients were included if they were aged 13-44 and received either 1) laboratory testing for chlamydia or gonorrhea or 2) an ICD-10 diagnosis of chlamydia, gonorrhea, or an unspecified STI. To validate ICD-10 codes, we calculated positive and negative predictive values, sensitivity, and specificity based on the presence of a laboratory test result, or any STI laboratory test results in case of unspecified STI. We further examined the timing of clinical diagnosis relative to laboratory testing. Results A total of 238,876 individuals (16.0% of population) were either tested for chlamydia or gonorrhea, or diagnosed with an ICD-10 code of interest, during the study period. For cases in which a patient was diagnosed with chlamydia or gonorrhea, 82% and 78% of cases were confirmed, respectively. The positive predictive values for chlamydia, gonorrhea, and unspecified STI ICD-10 codes were 87.6%, 85.0%, and 32.0%, respectively. Negative predictive values were high (>92%). Sensitivity for chlamydia diagnostic codes was 10.6% and gonorrhea was 9.7%. Specificity was 99.9% for both chlamydia and gonorrhea. Conclusions Disease specific ICD-10 codes accurately identify cases of chlamydia and gonorrhea. However, low sensitivities suggest that most gonorrhea and chlamydia cases could not be identified in administrative data alone without laboratory test results. Key messages Disease specific ICD-10-CM codes accurately identify cases of chlamydia and gonorrhea. Low sensitivities suggest that most gonorrhea and chlamydia cases could not be identified in administrative data alone without laboratory test results.