[Multivariate analysis of blood culture positive rate of ICU patients]

To investigate the factors associated with positive results of blood culture and the impact of positive results on the prognosis of patients in ICU of Peking University People's Hospital.

We retrospectively analyzed 1 008 blood culture results of 379 critical ill adult patients in ICU from July 1st, 2013 to June 30th, 2014. According to blood culture results, the patients were divided into positive and negative groups. The patients' maximal body temperature, sample collection times, number of bottles within 24 hours, routine hematological variables [(white blood cell count (WBC), percentage of neutrophils (NEU%), lymphocyte count (LYM), platelet count (PLT)], serum C-reactive protein (CRP), usage of antibiotics were compared between the two groups, as well as the patients' gender, age, duration of mechanical ventilation, length of ICU stay and hospital mortality rate.

The total positiverate of blood culture of our study was 15.38%, and the positive rate of patients was 24.27%.When compared between positive group and negative group, the medians of sample collection times were 3 and 1(P<0.000 1); the medians of sample bottles were 4 and 4(P=0.001 2); the medians of WBC were 8.61×10(9)/L and 9.95×10(9)/L(P=0.001 7); and the medians of mechanical ventilation time were 179.5 hours and 47 hours(P<0.000 1); the medians of length of ICU stay were 17 days and 7 days(P<0.000 1), respectively. Hospital mortality rates in positive patients and negative patients were 35.87% and 20.21%(P=0.002 2), respectively. There was no significant difference(P>0.05) between the two groups in body temperature, NEU%, LYM, PLT, CRP or usage of antibiotics.

Increasing the frequency of sampling and the bottles of blood culture will improve the positive rate of blood culture. The body temperature, WBC, NEU%, LYM, PLT, CRP, us age of antibiotics, gender and age have no effect on the positive rate of blood culture. The patients with positive blood culture results have longer duration of mechanical ventilation, longer ICU stayand higher hospital mortality rate.