Abstract:

Objective To evaluate the performance of a blood gas analyzer,to compare the internal quality control（IQC） results from both the automatic quality control（QC） data in the instrument and external manual QC data according to Westgard sigma rules,and to guide the IQC scheme and improve the measurement performance. Methods Parameters,such as coefficient of variation（CV） and bias（Bias）,were used. Allowable total error（TEa） was provided by the Clinical Laboratory Improvement Amendments of 1988（CLIA'88） standard or instruction from the manufacturer. The sigma（σ） values for 16 blood gas items in the automatic and external manual IQC systems were calculated,respectively. Corresponding QC scheme was designed according to Westgard sigma rules,and the consistency rates of the 2 IQC systems were analyzed. Results Among all the 16 blood gas items,the measurement performance of partial pressure of oxygen [p（O₂）] was <3σ,while the other items showed measurement performance >5σ,and 14 items reached 6σ. According to Westgard sigma rules,there were inconsistencies between the automatic and external manual IQC results for items including p（O₂）,pH and partial pressure of carbon dioxide [p（CO₂）]. The consistency rates were 36.11%,94.44% and 93.06% for p（O₂）,pH and p（CO₂）,respectively,while 100% for the others. Conclusions The measurement performance of this blood gas analyzer is good except that the analyzing quality of p（O₂） needs to be improved. Compared with the external manual IQC,the results of automatic QC system in the instrument are relatively stable and easy to operate. However,external manual IQC may include more error causing factors rising from other sources. The automatic QC system in the instrument should adopt reasonable IQC rules and cooperate with external IQC to ensure that the clinical laboratory provides objective and reliable indicators for clinical use.

Key words: Blood gas analysis, Westgard sigma rule, Quality control, Point-of-care testing