Administrative data has poor accuracy for surveillance of Staphylococcus aureus bacteraemia

Background To determine the accuracy of the International Classification of Diseases (ICD-10) coding for Staphylococcus aureus bacteremia (SAB) compared with laboratory results during a ten-year period (January 2002–December 2011). Methods A retrospective comparison of ICD-10 code A41.0 for S. aureus sepsis with SAB identified from the laboratory information system (LIS). Patients with LIS identified SAB (LIS+) and/or the ICD-10 A41.0 code (ICD-10) were identified and classified as concordant (LIS+/ICD+) or discordant (LIS+/ICD− or LIS-/ICD+). From July 2010 an additional code for healthcare associated SAB (HA-SAB), U90.0, was introduced and evaluated against prospectively designated episodes of HA-SAB. Results and Conclusions There were 740 laboratory confirmed episodes of SAB however, only 408 of these were recorded by ICD-10 A41.0whilst 106 patients with negative blood cultures were miscoded as ICD-10 A41.0. The sensitivity and PPV for ICD-10 A41.0 were 55% [95% CI: 51–59%] and 72% [95% CI: 68–76%]. For the subset of HA-SAB, the sensitivity and PPV for ICD-10 U90.0 were only 12% [95% CI: 5–24%] and 32% [95% CI: 15–54%] respectively. Surveillance based solely on ICD-10 A41.0, code underestimates the true incidence of SAB even while including non-bacteremic episodes. ICD-10 U90.0 for HA-SAB has even poorer sensitivity and PPV. Laboratory culture results should become the major criterion for ICD-10 coding for SAB to improve the accuracy of surveillance data.