ICD-9 code reporting among patients from the Minnesota SARI surveillance program

The ICD-9 codes for acute respiratory illness (ARI) and pneumonia/influenza (PI however, few studies evaluate the accuracy of these codes or the importance of ICD-9 position. We reviewed ICD-9 codes reported among patients identified through severe acute respiratory infection (SARI) surveillance to compare medical record documentation with medical coding and evaluated ICD-9 codes assigned to patients with influenza detections. Methods The Minnesota Department of Health (MDH) conducted SARI surveillance at three hospitals. All hospitalized patients with submission of a physician-ordered upper respiratory specimens (e.g., sputum, throat or nasopharyngeal swabs) were enrolled. A medical chart review was conducted to identify those meeting SARI criteria, defined as patients admitted to an inpatient ward with new onset of respiratory symptoms or acute exacerbation of chronic respiratory conditions. Enrolled patients who did not meet the SARI criteria were categorized as non-SARI. Residual material from the upper respiratory specimens were submitted to MDH for influenza testing by RT-PCR. Demographic and clinical data, including up to eight ICD-9 codes, were collected through the medical record review. Patients with an ICD-9 code indicating ARI (460 to 466) or PI an ARI/P&I code in the first position was found in 40% of SARI vs 7% of non-SARI patients (OR=8.6, 95% CI 7.0-10.5). Among SARI patients with at least one ARI/P&I code, 66% had their first or only ARI/P&I code in the 1 st position, 25% in the 2 nd position, and 6% in the 3 rd position. For identification of SARI, sensitivity/specificity was 61%/84% for ARI/ P&I codes in any position and 40%/93% for ARI/P&I codes in the 1 st position. Among SARI patients, codes for pneumonia (486) and acute bronchiolitis (466.11, 466.19) were commonly reported. The most frequent codes among SARI patients without an ARI/P&I code were fever (780.6), acute respiratory failure (518.81), and asthma (493.92) (Table). Influenza was detected among 8% (351) of SARI patients. An ARI/P&I code in any position was more common in influenza- positive vs. influenza-negative SARI patients (77% vs 59%, OR 2.4, 95% CI 1.8-3.1). An ARI/P&I code in the 1 st position was slightly more common in influenza-positive vs -negative patients though not significant (44% vs 40%). Conclusions Among patients from whom a respiratory specimen was collected, administrative data identified those meeting SARI with moderate sensitivity and high specificity, and with lower sensitivity but greater specificity when limited to the 1 st ICD-9 position. Pneumonia and acute bronchiolitis ICD-9 codes were frequent ARI/P&I codes among SARI patients. Further investigation is needed to determine the value of including additional ICD-9 codes, such as respiratory distress and acute asthma exacerbation, in identifying SARI.