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Jornal Brasileiro de Patologia e Medicina Laboratorial

Print version ISSN 1676-2444


CORREA, Karoline de Lemes Giuntini; ALMEIDA, Gisele Madeira Duboc de; ALMEIDA JUNIOR, João Nobrega de  and  ROSSI, Flávia. Differential time to positivity: a useful tool for the diagnosis of catheter-related infections?. J. Bras. Patol. Med. Lab. [online]. 2012, vol.48, n.3, pp.195-202. ISSN 1676-2444.

INTRODUCTION: Not only do catheter related bloodstream infections (CRBSIs) have considerable impact on morbidity and mortality in hospitalized patients, but they also raise hospital costs. The use of automated equipment in blood culture processing has allowed an alternative diagnosis of CRBSI by analyzing the differential time to positivity (DTP) of paired blood cultures (collected simultaneously) of peripheral blood and catheter blood. A rapid and accurate diagnosis of these infections may optimize clinical and therapeutic management, which prevents early catheter removal. OBJECTIVES: To assess DTP as an auxiliary tool for the diagnosis of CRBSI as well as to determine the main isolated microorganisms. METHODS: We evaluated blood cultures that had previously been collected in the complex Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo (HC/FMUSP) from May to August 2008. According to the laboratory criteria, only DTP higher than 120 minutes was regarded as possible CRBSI. RESULTS: During the investigation period 11,017 aerobic blood cultures were processed, from which only 5% were paired samples. One hundred forty-eight (28%) samples were positive, from which 9% showed growth in peripheral blood, 41% only in catheter blood and 50% in both blood samples with 88% homology of identified microorganisms. DTP higher than 120 minutes occurred in 50% of the cases. The most common isolated microorganisms were: Staphylococcus aureus (22%), Candida spp. (18%), Klebsiella spp (7%). and Enterobacter spp (7%). CONCLUSION: The determination of the DTP as an auxiliary tool for the diagnosis of CRBSI is feasible and easily performed in clinical laboratories with automation, although the process of paired sample collection must be rigidly standardized.

Keywords : Catheter related bloodstream infections; Differential time to positivity; Central venous catheter; Hospital infections.

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