Use of active surveillance to validate International Classification of Diseases code estimates of rotavirus hospitalizations in children

Objective. National estimates of hospitalizations for rotavirus, the leading cause of acute gastroenteritis ( AGE) in children, have been used to establish the need for rotavirus vaccines. A previous method directly estimated discharges by using the rotavirus-specific International Classification of Diseases (ICD) code, but this method has not been validated. Our study evaluated the sensitivity of the rotavirus ICD code among children hospitalized for AGE by using active surveillance for rotavirus at a tertiary children's hospital. Design. We compared data for rotavirus-coded hospital discharges in 2000-2001 at Cincinnati Children's Hospital Medical Center with data on laboratory-confirmed cases of rotavirus obtained from active surveillance. We estimated additional rotavirus hospitalizations by extrapolating the proportion of rotavirus-positive results from active-surveillance cases to those with an unknown rotavirus status. Results. Of 767 cases of AGE-related discharge codes, 103 (13%) were coded as rotavirus, 91% ( 94 of 103) of which were laboratory-confirmed diagnoses. Among all children discharged with an AGE-related illness, 260 (34%) were enrolled in active surveillance, of whom 155 (60%) tested positive for rotavirus. An additional 47 laboratory-confirmed rotavirus-case patients not enrolled in active surveillance yielded a total of 202 rotavirus cases and a maximum sensitivity of the rotavirus code of 47%. Extrapolation indicated that an additional 170 untested children might be rotavirus- positive, yielding a total of 372 rotavirus hospitalizations and a minimum sensitivity of the rotavirus code of 25%. Conclusions. Measurement of rotavirus- coded hospital discharges alone seems to greatly underestimate the true burden of rotavirus- associated hospitalizations. The numbers of national rotavirus hospitalization discharges may be substantially greater than previously estimated.