A case-definition for national and international neonatal bloodstream infection surveillance
Neena Modi 1*, Caroline J Doré 2, Arun Saraswatula 1, Michael Richards 3, Kathleen B Bamford 1, Rosa Coello 1 and Alison Holmes 1
1 Imperial College London, United Kingdom
2 Medical Research Council, United Kingdom
3 Hammersmith Hospitals NHS Trust, United Kingdom
* To whom correspondence should be addressed. E-mail: n.modi{at}imperial.ac.uk.
Accepted 13 May 2008
 | Abstract |
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Objective: Neonatal bloodstream infection (BSI) is a major contributor to mortality, health service costs, and the population burden of life-long ineurodisability. BSI surveillance, an essential component of infection control, requires an unambiguous standardised case-definition as variability would invalidate any comparative analyses. In neonates a high proportion of blood cultures yield a mixed growth or skin commensals, principally coagulase-negative staphylococci (CoNS). As this might represent either genuine BSI or contamination, clinical correlates are necessary, but this adds to the difficulty of agreeing an objective, standardised case-definition.
Design: Utilising data from 26 UK neonatal units, we evaluated the population prevalence of 12 predefined clinical signs of infection captured daily for 28 days. We determined the sensitivity, specificity, odds ratio and positive predictive value of each sign and sequential numbers of grouped signs to develop a predictive model for a positive blood culture. We used sandwich estimates of the standard errors of the logistic regression coefficients to take account of the correlations between these repeated measures. We tested this model in an independent data set.
Results: Three or more clinical signs had the best predictive accuracy for a positive blood culture (76.2% specificity; 61.5%, 46.9% and 78.2% sensitivity for all positive cultures, cultures yielding CoNS, or a recognised pathogen, respectively).
Conclusion: We suggest that a simple case-definition for national and international neonatal BSI surveillance is provided by a blood culture yielding a recognised pathogen in pure culture; or a mixed growth or skin commensal plus 3 or more pre-defined clinical signs.
