An interlaboratory survey of hydrogen ion and blood gas determinations

A survey of [H+], Pco2, and Po2 analyses in 360 laboratories was conducted using three commercial control materials: two aqueous gas-equilibrated buffer solutions (General Diagnostics and IL) and one whole blood material (DADE). There was little difference in precision or accuracy between instruments, classified according to manufacturer into four groups, and materials for [H+] and Pco2, or in precision for Po2. There were, however, differences in accuracy between instrument groups for Po2 analysis on the aqueous materials, and in some cases the mean values lay outside the range assigned by the material manufacturers. The 35 instruments outside clinical chemistry departments yielded results similar to those of all participants. The relation between inter- and intra-laboratory precision was similar to that for many analytes, suggesting that neither these materials nor the state of these analyses is unsatisfactory. Aqueous materials should, however, be used with caution as accuracy controls for Po2.