Positive predictive values of the International Classification of Diseases, 10th revision diagnoses of Gram-negative septicemia/sepsis and urosepsis for presence of Gram-negative bacteremia

Background: Health care databases are a valuable resource for infectious disease epidemiology if diagnoses are accurately coded. We examined the ability of diagnostic coding to accurately identify Gram-negative bacteremia. Methods: We randomly selected 100 patients among 1,703 patients recorded in the Danish National Patient Register with a diagnosis of either septicemia/sepsis due to other Gram-negative organisms (International Classification of Diseases, 10th revision [ICD-10] code A41.5) or urosepsis (ICD-10 code A41.9B) who had been admitted at Aalborg University Hospital, Denmark between 1994 and 2012. We estimated the positive predictive value (PPV) of these diagnoses for presence of Gram-negative bacteremia, using microbiological results from blood cultures as standard reference. Complementary clinical information was obtained from the medical records. Results: Of the 100 patients registered with Gram-negative septicemia/sepsis or urosepsis, 72 had blood culture confirmed Gram-negative bacteremia, four patients had monomicrobial Gram-positive bacteremia, 21 patients had a negative blood culture, and three had no blood culture taken. The overall PPV of a blood culture confirmed Gram-negative bacteremia diagnosis was 72% (95% confidence interval [CI]: 62%-81%); for ICD-10 code A41.5 it was 86% (95% CI: 74%-94%) and for ICD-10 code A41.9B it was 55% (95% CI: 39%-70%). The highest PPV was achieved for diagnoses registered in the most recent calendar period (2009-2012) and for secondary discharge diagnoses. Conclusion: Our findings indicated good agreement between ICD-10 code A41.5 septicemia/sepsis due to other Gram-negative organisms and Gram-negative bacteremia, whereas ICD-10 code A41.9B urosepsis was not suited for identification of Gram-negative bacteremia.