This guideline is a consolidation of six CLSI documents and projects. The Area Committee on Clinical Chemistry and Toxicology concluded that CLSI’s constituencies (professions, government, and industry) would be better served with the production of a single document that retains the essential information from the six original documents, while making it even more relevant and useful. It addresses blood gas, pH, and related measurements (eg, hemoglobin and hemoglobin fractions, oxygen content, hemoglobin-oxygen saturation, electrolytes, and selected metabolites) as measured in blood. It defines terminology and discusses performance characteristics as well as preanalytical variables and analytical considerations. It also addresses quality control issues.

This guideline consolidates and updates previously published CLSI/NCCLS documents C12-A—Definitions of Quantities and Conventions Related to Blood pH and Gas Analysis; Approved Standard; C21-A—Performance Characteristics for Devices Measuring pO2 and pCO2 in Blood Samples; Approved Standard; C25-A—Fractional Oxyhemoglobin, Oxygen Content and Saturation, and Related Quantities in Blood: Terminology, Measurement, and Reporting; Approved Guideline; C27-A—Blood Gas Preanalytical Considerations: Specimen Collection and Controls; Approved Guideline; and C32-P—Considerations in the Simultaneous Measurement of Blood Gases, Electrolytes, and Related Analytes in Whole Blood; Proposed Guideline; and unpublished CLSI document C33—Practical Blood Gas and pH Quality Control.

Sections of another CLSI document H11 also are included; however, H11 will remain a separate document, because its content is of interest to a broader audience.

The current revision of the document, C46-A2, includes the following updates: 

• Section 5, Preanalytical Considerations, was expanded to include a discussion specific to transport of specimens (see Section 5.3). Section 5.4, In Vivo Effects on Measurements, replaces the former section, Patient Condition, and was expanded. 

• Section 6, Analytical Interferences, was expanded significantly, including references to recent literature. 

• Section 7, Blood Gas Analyzer Calibration, was expanded significantly, including current requirements for calibration traceability. 

• Section 8, Blood Gas Quality Control, includes newer approaches for “alternative” quality control. 

• Appendix B, Recommendations for Measurement and Reporting of Hemoglobin Fractions and Related Quantities, was added. 

• Appendix C, Measurement Technologies Used in Instruments for Analysis of Blood Gases, pH, and Related Analytes, was added.

This guideline addresses blood gas, pH, and related measurements (eg, hemoglobin and hemoglobin fractions, oxygen content, hemoglobin-oxygen saturation, electrolytes, hematocrit, glucose, and lactate) as measured in blood. The guideline is limited to devices for measurement of these quantities in vitro. Devices for in vivo monitoring and patient-attached, ex vivo monitors for blood gas, pH, and related measurements, although common in many respects to devices for in vitro measurements, are not specifically addressed. 

This document defines terminology and discusses performance characteristics as well as preanalytical variables, analytical considerations, and quality control (QC) issues. 

This guideline is primarily intended for laboratory technologists, respiratory therapists, critical care practitioners, and others responsible for obtaining and analyzing blood for pH, oxygen, carbon dioxide, and related measurements. It will also be useful to manufacturers and those responsible for teaching this subject to medical students, residents, and allied health personnel.