Regional Quality Control Survey of Blood-Gas Analysis

Abstract

We undertook an external quality control survey of blood-gas analysis in 16 laboratories at 13 hospitals. All samples were prepared in the laboratories under investigation by equilibration of blood or serum with gas mixtures of known composition. pH of serum was measured with no significant bias but with an SD of random error 0·026 pH units, which was almost twice the SD of the reference range (0·015). An acceptable random error (half SD of reference range) was not obtained in a longitudinal internal quality control survey although there were acceptable results for buffer pH in both field and internal surveys. Blood Po2 was measured with no significant bias but with SD of random error 1·38 kPa which reduced to 0·72 kPa by excluding one egregious result. The latter value was just over half of the SD of the reference range (1·2 kPa). Pco2 of blood was also measured without significant bias but with a much smaller SD of random error of 0·28 kPa (by excluding one egregious result), which was again just over half the SD of the reference range (0·51 kPa). Measurements of blood Po2 and Pco2 seem generally acceptable in relation to their respective reference ranges but measurements of pH were unsatisfactory in both internal and external trials.

An Interlaboratory Survey of Hydrogen Ion and Blood Gas Determinations

“…These results are similar to those obtained for all participants, shown in Tables I to 3, confirming the observation of Minty and Nunn (1977) that instruments used outside clinical chemistry laboratories do not exhibit worse performance than those in departments of clinical chemistry. It must be realised, however, that laboratories participated voluntarily in these surveys, and those laboratories with a greater awareness of quality control and desire to check the comparability of their results would therefore tend to be selected preferentially.…”

“…The CVs observed for [H+], PC02, and P02 are approximately double those reported in withinlaboratory trials using similar materials assayed over several weeks on one instrument (Evans, 1978;Minty and Nunn, 1977). This difference between within-laboratory precision and total betweenlaboratory, between-instrument precision is similar to that observed for many other analytes (Whitehead et al, 1973) and suggests that neither the materials used in this study nor the present state of [H +] and blood gas analysis is poor with regard to precision.…”

“…Recent between-laboratory comparisons have suggested that significant discrepancies can exist in the analysis of [H +], PC02, and P02 (Isherwood et al, 1972;Dowd and Jenkins, 1973;Weisbrot et al, 1974;Minty and Nunn, 1977). The number of partieipating laboratories was small-no more than 16 in any of these surveys-and the organisers of the UK National Quality Control Scheme (NQCS; Whitehead et al, 1973) therefore decided to conduct a survey of [H +], PC02, and P02 measurement which would include a large number of instruments, both within and outside clinical chemistry departments.…”

A Comparison of Two Methods of Quality Control of pH, Pco2, and Po2 Measurements

“…4KOll, cision control for pH measurements and an accuracy 4KOIO, 4KOO9). The same measurements were also and precision controlfor Pcos and Posmeasurements made on a tonometered phosphate-bicarbonate- (Bird and Henderson, 1971;Minty and Nunn, 1977). chloride solution in a glycerol-water mixture (4) A buffer made up in glycerol-water mixtures and (Veefkind et al, 1975).…”

Quality Control in Clinical Chemistry Laboratories

“…A recent study (Minty and Nunn, 1977) has supplied data on the levels of accuracy attained in a sample of 16 laboratories in the north-west region of the UK. The study involved the analysis of blood of known P02 and PC02 and serum of known pH.…”