[Less blood culture samples: less infections?].

Background: The data of the German hospital nosocomial infection surveillance system (KISS) were used to investigate the association between the frequency of blood cultures (BC) and central venous catheter associated bloodstream infection (CVC-BSI) rates in intensive care units (ICU).

Methods: A questionnaire on the frequency of BCs taken was sent to all ICUs participating in KISS and univariable and multivariable analyses were performed on the results.

Results: A total of 223 ICUs provided data. The median number of BC pairs taken in 2006 was 60 with a huge variation from 3.2 to 680 per 1,000 patient days. The mean primary BSI rate was 0.90 per 1,000 patient days and 0.25 BSIs per 1,000 patient days were caused by coagulase negative Staphylococci (CNS). The mean CVC-BSI rate was 1.40 per 1,000 CVC days. In the univariable analysis the blood culture frequency had a significant influence on the CVC-associated BSI rate, considering either all pathogens (p=0.001) or only the subgroup of CNS-related cases (p=0.019). There was also a significant influence of the BC frequency on the CVC-BSI rate considering all pathogens (p=0.004) as well as the subgroup of CNS (p=0.018). Therefore the BC frequency was a significant factor affecting the incidence of BSI and CVC-BSI. According to the multivariable analysis an increase of the BC frequency of 100 BCs per 1,000 patient days leads to a 1.27-fold higher incidence density of CVC-BSI with a 95% confidence interval (95% CI) of 1.01-1.26. A further significant risk factor for CVC-BSI was the length of stay in the ICU with an adjusted incidence rate ratio (IRR) of 1.25 (95% CI 1.15-1.35). To have the status of an interdisciplinary ICU was a significant protective factor (IRR 0.64; 95% CI 0.45-0.92).

Conclusions: If an external benchmarking of ICU CVC-BSI rates is intended an adjustment according to the BC frequency is necessary. The BC frequency itself should be established as a quality indicator in intensive care.