Validation of intensive care unit-acquired infection surveillance in the Italian SPIN-UTI network

Validity is one of the most critical factors concerning surveillance of nosocomial infections
(NIs). This article describes the first validation study of the Italian Nosocomial Infections
Surveillance in Intensive Care Units (ICUs) project (SPIN-UTI) surveillance data. The objective
was to validate infection data and thus to determine the sensitivity, specificity, and positive
and negative predictive values of NI data reported on patients in the ICUs participating in
the SPIN-UTI network. A validation study was performed at the end of the surveillance period.
All medical records including all clinical and laboratory data were reviewed retrospectively by
the trained physicians of the validation team and a positive predictive value (PPV), a negative
predictive value (NPV), sensitivity and specificity were calculated. Eight ICUs (16.3%) were
randomly chosen from all 49 SPIN-UTI ICUs for the validation study. In total, the validation
team reviewed 832 patient charts (27.3% of the SPIN-UTI patients). The PPV was 83.5% and the
NPV was 97.3%. The overall sensitivity was 82.3% and overall specificity was 97.2%. Over- and
under-reporting of NIs were related to misinterpretation of the case definitions and deviations
from the protocol despite previous training and instructions. The results of this study are
useful to identify methodological problems within a surveillance system and have been used to
plan retraining for surveillance personnel and to design and implement the second phase of
the SPIN-UTI project.