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Scientific Institute of Public Health. Data validation study of the Belgian national surveillance of nosocomial infections in intensive care units. Ann Versporten, Ingrid Morales, Carl Suetens. 4 th Congress of the International Federation of Infection Control – Malta November 11, 2003.
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Scientific Institute of Public Health Data validation study of the Belgian national surveillance of nosocomial infections in intensive care units Ann Versporten, Ingrid Morales, Carl Suetens 4th Congress of the International Federation of Infection Control – Malta November 11, 2003
Background: Belgian National ICU surveillance • 1996: Start National Surveillance of ICU acquired infections (Pneumonia & Bacteraemia) • ICU acquired : admitted >48h in ICU • patient-based surveillance: 1 file by patient, + infection file if ICU-acquired PN or BAC
Validation study : main aim • Determination of Sensitivity & Specificityof reported ICU-surveillance data (PN & BAC) against a reference gold standard • Evaluate the accuracy of all data reported to the surveillance • Exhaustiveness (completeness) of the denominator
Methods : sample size • Anticipated: Se = 65% ± 5% Sp = 99.5% ± 0.5% Prevalence of 7% • 1300 patient charts in a total of 45 hospitals : • 268 PN + • 128 BAC + (declared BAC on blood culture list) • 904 PN – (= 20% of total PN-) • Exhaustiveness of denominator: estimation on the base of administrative lists of ICU-admissions
Methods (next) • Retrospective patients chart review methodology • Research team = “gold standard” • trained data collectors (NSIH team) • application protocol definitions • evaluation = blind • discrepant infections: reviewed by other colleague
Results (ongoing, n=33 hosp.) Exhaustiveness of denominators : 81,2% for all patients staying >48h in ICU
Discussion • PN & BAC : low Se., good Sp. • 50% of the collected data concern the 3 first surveillance quarters that hospitals participated to our ICU surveillance • Exhaustiveness denominator: improvement possible
Who are those missed patients ?? Why are there so many false negative Pneumonias ?
Factors influencing the Se. & Sp. of the infection data • Who collects data ? • Who decides whether a PN should be reported or not ? • Criteria used for blood culture? • Adherence to protocol definitions • Degree of workload (ratio patient/staff) • Size of hospital • …
Conclusions • Exhaustiveness varies by hospital, but remains satisfactory in general • BAC more accurately reported than PN (Se) • Seldomly infections reported which were not a nosocomial infection (Sp) • half of FP were infections at entry (47%) • Absence of a gold standard ! • problem for diagnostic of PN, certainly those without identification of a micro-org.
What have we learnt ? • Improve Sensitivity • Improve case finding by • Good communication and training data collectors at hospital level • Importance of electronic surveillance • Surveillance = a standardised tool to measure nosocomial infections Surveillance = not an audit