Endogenous Interference Impairs Arterial Blood Gas Analysis

Blood samples that show hemolysis, lipemia, or icterus may be unsuitable for arterial blood gas analysis (ABG) as these indices affect the results.

The modern ABG analyzers enables rapid analysis of traditional blood gas elements such as pH, partial pressure of carbon dioxide (pCO2) and oxygen partial pressure (pO2), and oxygen saturation as well as clinical chemistry parameters, all of which rely on the quality of the specimens.

Scientists at the University of Verona (Italy) analyzed 478 ABG specimens received in their laboratory throughout a two-month study period. The serum indices (SI) were assessed after all routine and stat samples referred for ABG analysis to the clinical laboratory using RAPIDPoint 400/405 Systems, Arterial Blood Gas Analyzer were completed. The SI of plasma was then assessed on the Cobas C501 after centrifugation. Interference cut-off values were 60 for Hemolysis Index (HI, i.e., cut-off of visible hemolysis), 30 for Lipemia Index (LI, i.e. Lipemic index is determined by the turbidity qualitatively with no units) and two for Icteric Index (II).

Out of a total of 478 ABG specimens received in the laboratory throughout the two month study period, 132 (27.6%) displayed at least one SI exceeding the cut-off. This could be further categorized as 44/162 (27.2%) from the emergency department, and 88/316, (28.6%) from the clinical wards. In particular 17 samples (4%) were characterized by HI exceeding 60, 52 samples (11%) by a LI exceeding 30, and 63 (13%) by II exceeding two. The frequency of hemolyzed specimens referred from the emergency department was double that of samples referred from the clinical wards.

The RAPIDPoint 400/405 Systems, Arterial Blood Gas Analyzer is a product of Siemens Medical Solutions (Munich, Germany) and the Cobas C501 is manufactured by Roche (Basle, Switzerland). The authors concluded that that a significant number of AGB specimens sent to their laboratory were characterized by elevated values of the SI, which could make them unreliable for testing. In particular, the frequency of HI greater than 60 was remarkably higher for samples referred from the emergency department than in those from the clinical wards, thereby confirming the trend already observed for clinical chemistry, immunochemistry, and coagulation testing. The study was published in the March 2012 issue of the journal Clinical Biochemistry.

Related Links:
University of Verona
Siemens Medical Solutions
Roche