Studies of one invasive and two noninvasive methods for detection of bacterial contamination of platelet concentrates.

Recently, a new method for noninvasive detection of bacterial contamination of platelet concentrates was described [Arpi et al.: Vox Sang 1993;65:335-336]. A CO2-sensitive label is applied on the outer surface of the plastic container of the platelet concentrate. When any contaminating bacteria have increased the pCO2 to a certain level the label changes color, indicating bacterial growth. We have studied this technique and applied such sensitive labels both directly onto PCs and onto plastic bags with culture medium into which platelet contents have been transferred. However, in both cases the sensitivity of the technique was found insufficient for practical quality control of PCs. There seem to be two problems with this principle: (1) platelets produce CO2 and (2) a considerable amount of the gas passes beside the detection label, in this way decreasing the sensitivity of detection by the label. This noninvasive technique was compared with an invasive method using automated bacterial culture, which was found sensitive and rapid.