CAP blood gas survey--first year's experience.

There were over 500 participants in the first year of the Survey. Ninety per cent identified themselves as clinical chemistry/pathology laboratories. Of the three analytes, pH was determined with the best interlaboratory precision and PO2 the lowest. Evaluation of accuracy was not possible because of the lack of an acceptable reference method. Interinstrument differences could be demonstrated by using all-methods results as a point of reference. Differences were more related to each individual instrument than to manufacturer. Because the survey specimens were buffered aqueous solutions that do not have all the characteristics of blood, results should be interpreted with caution. Some of the results, especially but not exclusively PO2, are artifacts of the survey material rather than a reflection of the state of the art of pH and blood gas analysis.