Blood samples Blood samples for PCT measurements were collected by the nursing staff in the ICU on a daily basis between 6.00 a.m. and 7.30 a.m. in accordance with the assumed half life of PCT. PCT analyses were performed by laboratory technicians at the Department of Clinical Microbiology, using an immunoluminometric assay (Lumitest-PCT, B.R.A.H.M.S. Diagnostica, Berlin, Germany). The threshold of detection was 0.1 ng/ml serum, according to the manufacturer.