Evaluation of protein containing quality control materials for blood gas analysis

Protein containing quality control (QC) material in ampoules for blood gas, pH and electrolyte analysers has been manufactured using buffered protein (Bovine Serum Albumine, BSA) solution with sodium bicarbonate and chloride salts. For comparison a similar QC material but without protein was manufactured. Results obtained with ampouled QC material depend on pre-analytical effects, on matrix effects and on the stability of the material. Pre-analytical variation occurs with closed and/or opened ampoules. The shaking rate of the ampoule must be high (vortexing) and the duration of shaking long enough (15 seconds) to give good reproducibility. Temperature coefficients of protein containing controls are equal to those of protein free controls when incubated at different temperatures. Vigorously shaking of the ampoule gives a protein foam layer resulting in stable values for pH, pCO2 and pO2 during maximally 6 minutes after opening of the ampoule. Concerning matrix effects the CO2 buffer capacity of protein containing QC material is slightly higher compared to that of protein free QC materials as determined by tonometry with CO2/air gas mixtures and measuring pH and plotting log pCO2 vs. pH. The O2 buffer capacity measured as the bias on a properly functioning blood gas analyser is smaller than the bias of protein free QC material. The protein containing quality control is stable for at least 12 months when stored refrigerated at 2-6 degrees C and 28 days at room temperature.