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Title: Surveillance for Clostridium difficile infection: ICD-9 coding has poor sensitivity compared to laboratory diagnosis in hospital patients, Singapore
Authors: Chan M.
Lim P.L. 
Chow A. 
Win M.K.
Barkham T.M. 
Keywords: Clostridium toxin
Clostridium difficile infection
comparative effectiveness
controlled study
diagnostic accuracy
diagnostic test
diagnostic test accuracy study
disease surveillance
hospital admission
hospital discharge
hospital infection
hospital patient
intermethod comparison
international classification of diseases
laboratory diagnosis
major clinical study
sensitivity analysis
sensitivity and specificity
toxin analysis
Clostridium difficile
comparative study
diagnosis, measurement and analysis
health survey
middle aged
pseudomembranous colitis
Clostridium difficile
Age Factors
Clostridium difficile
Enterocolitis, Pseudomembranous
International Classification of Diseases
Laboratory Techniques and Procedures
Middle Aged
Population Surveillance
Sensitivity and Specificity
Issue Date: 2011
Citation: Chan M., Lim P.L., Chow A., Win M.K., Barkham T.M. (2011). Surveillance for Clostridium difficile infection: ICD-9 coding has poor sensitivity compared to laboratory diagnosis in hospital patients, Singapore. PLoS ONE 6 (1) : e15603. ScholarBank@NUS Repository.
Rights: Attribution 4.0 International
Abstract: Introduction: Clostridium difficile infection (CDI) is an increasingly recognized nosocomial infection in Singapore. Surveillance methods include laboratory reporting of Clostridium difficile toxin assays (CDTA) or use of International Classification of Diseases, 9th Revision (ICD-9) discharge code 008.45. Previous US studies showed good correlation between CDTA and ICD-9 codes. However, the use of ICD-9 codes for CDI surveillance has not been validated in other healthcare settings. Methods: We compared CDI rates based on CDTA to ICD-9 codes for all discharges in 2007 from our hospital to determine sensitivity and specificity of ICD-9 codes. Demographic and hospitalization data were analyzed to determine predictors for missing ICD-9 codes. Results: During 2007, there were 56,352 discharges. Of these, 268 tested CDTA-positive but only 133 were assigned the CDI ICD-9 code. A total of 141 discharges had the ICD-9 code; 8 were CDTA-negative, the rest were CDTA-positive. Communityacquired CDI accounted for only 3.2% of cases. The sensitivity and specificity of ICD-9 codes compared to CDTA were 49.6% and 100% respectively. Concordance between CDTA and ICD-9 codes was 0.649 (p<.001). Comparing concordant patients (CDTA+/ICD9+) to discordant patients (CDTA+/ICD9-), concordant patients were more likely to be over 50 years of age (OR 3.49, 95% CI 1.66-7.34, p=.001) and have shorter time from admission to testing (OR 0.98, 95% CI 0.97-0.99, p=.009). Discussion: Unlike previous studies in the US, ICD-9 codes substantially underestimate CDI in Singapore compared to microbiological data. Older patients with shorter time to testing were less likely to have missing ICD-9 codes. © 2011 Chan et al.
Source Title: PLoS ONE
ISSN: 19326203
DOI: 10.1371/journal.pone.0015603
Rights: Attribution 4.0 International
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