The validity of ICD-based codes to identify pediatric cases of congenital cytomegalovirus

Administrative claims databases are used to study the care of congenital cytomegalovirus (cCMV), yet the use of International Classification of Diseases, (ICD-9/10) codes for cCMV have not been validated. This study examines the accuracy of ICD-based codes for cCMV infection.

Infants cared for at a quaternary children's hospital (2013-2023) that had an ICD-based diagnosis for cCMV or CMV Infection at ≤90 days of age were included. Medical record data was abstracted. True Positive cases were defined as those with an ICD code AND clinical and laboratory evidence consistent with cCMV. False Positive cases were defined as those with an ICD code without evidence of cCMV. Positive predictive value (PPV) and sensitivity for each diagnostic code at different age cutoffs were calculated within the cohort. Multinomial regression examined characteristics of the infant with odds of being a True Positive case of cCMV.

Of the 108 infants with ICD-9/10 codes for cCMV, 35% were false positives. PPV for ICD-9/10-CM codes for cCMV, CMV Infection, and Either code predicting actual cCMV were 0.86, 0.36, and 0.68 at age ≤45 days. PPV was the highest at ≤21 days of age, and for all codes sensitivity increased with patient age. Multinomial logistic regression found the age of the first diagnostic code ≤21 days (vs. >) (OR = 4.11, 95% CI 1.45-12.03), having an ICD-9/10-CM diagnostic code of cCMV (vs. CMV Infection) (OR = 10.87, 95% CI 3.64-32.47), and having Clinical Signs at Birth (vs. none) (OR = 8.4, 95% CI 2.72-25.81) to be associated with greater odds of having a True Positive case of cCMV (vs. Not cCMV).

Administrative claims case definitions for cCMV were more likely to be accurate when assigned at a younger age. Studies using case definitions for cCMV that include the presence of codes for either cCMV or CMV Infection may be biased given the high proportion of false positives demonstrated in this study.