Influence of blood carbon dioxide pressure on growth index values in non-radiometric Bactec vials.

The influence of blood carbon dioxide pressure on growth index values yielded by the Bactec NR 660 system was evaluated. Growth index values of 1,175 Bactec blood culture vials collected from 293 patients were related to blood pCO2 and leukocyte concentrations. Thirty-three blood cultures were considered false-positive. These were significantly more frequently encountered in hypercapnia patients (5.4%) than in hypocapnia patients (1.7%) or normal patients (2.5%). There was no relationship between the growth index values and leukocyte concentrations.