Accuracy of Inpatient International Classification of Diseases, Ninth Revision, Clinical Modification Coding for Cytomegalovirus after Kidney Transplantation

Background International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) coding for cytomegalovirus (CMV) has been used as a proxy for active CMV infection or disease occurring in the inpatient setting in retrospective studies of kidney transplant recipients using large amounts of administrative data. However, the accuracy of inpatient CMV coding has not been determined. Methods We identified 393 kidney transplant recipients who were readmitted to Barnes-Jewish Hospital in St. Louis, Missouri from January 1, 2007 to December 31, 2011 to determine the accuracy of the ICD-9-CM diagnosis code for CMV (078.5) in identifying active CMV infection or disease (asymptomatic viremia, CMV syndrome, or tissue-invasive CMV disease) in the inpatient setting, using microbiological, histopathologic, or ophthalmologic evidence for CMV as the gold standard. Results The sensitivity and positive predictive value of CMV coding in identifying active CMV infection or disease were 0.77 and 0.71, respectively. The specificity and negative predictive value were both 0.98. The sensitivity of CMV coding in identifying CMV syndrome or tissue-invasive CMV disease was 0.93. Conclusions CMV coding had good accuracy in identifying active CMV infection or disease among readmitted kidney transplant recipients in our hospital. Further validation studies of CMV coding in other hospitals are needed to obtain more generalizable estimates of the accuracy of CMV coding.