Quality control of total carbon dioxide (CO2) in serum or plasma using the Abbott Architect is affected by environmental pCO2 concentrations.

Introduction: Total CO2, or bicarbonate, is a parameter in clinical chemistry often applied to assess the metabolic status of a patient. This article discusses the observations and interventions during an episode of assay instability on an Abbott Architect routine chemistry analyser.Results: The Levey-Jennings plot of QC data showed a circadian pattern, having an overestimation of total CO2 during periods of high personnel attendance. A qualitative analysis revealed a correlation between atmospheric CO2 in the lab environment and the acquired total CO2 value in a quality control sample. Assessment of total CO2 is hence influenced by the equilibrium between atmospheric CO2, dissolved CO2 and bicarbonate. The effect is more pronounced on samples containing low concentrations of total CO2. The bias related to environmental CO2 is also noticeable on patient samples, patient means between periods with high and low atmospheric CO2 levels differed by 2 mmol/L.Discussion: Passive ventilation of the laboratory environment is proven insufficient during weather conditions in which the lab is not exposed to wind. Consistent reduction of atmospheric CO2 could only be guaranteed with an active ventilation infrastructure. Systematic closure of analyser lids also reduced analyser variance.Conclusion: The lab environment is an important source of parameter variance. Both environmental and infrastructural aspects must be considered when assessing the potential cause of the instability.