DEVELOPMENT OF A BIPARAMETRIC BIOANALYSER FOR CREATININE AND UREA - VALIDATION OF THE DETERMINATION OF BIOCHEMICAL PARAMETERS ASSOCIATED WITH HEMODIALYSIS
M. Jurkiewicz et al., DEVELOPMENT OF A BIPARAMETRIC BIOANALYSER FOR CREATININE AND UREA - VALIDATION OF THE DETERMINATION OF BIOCHEMICAL PARAMETERS ASSOCIATED WITH HEMODIALYSIS, Analyst, 123(6), 1998, pp. 1321-1327
The construction and evaluation of an automated urea and creatinine bi
parametric biosystem using flow injection analysis (FIA) are described
. The biosystem uses enzyme reactions that hydrolyse urea and creatini
ne producing ammonium ions. The enzymes used were creatinine deiminase
and urease, which are immobilized covalently in flow reactors, The re
actor with creatinine deiminase has the enzyme immobilized on controll
ed-pore glass beads, whereas urease is immobilized on a nylon open tub
ular reactor. Detection is realised with a flow-through ammonium ion-s
elective electrode with an inner solid-state contact (graphite-epoxy c
omposite). Ammonium ions are separated from alkali ion interferents th
rough a gas-diffusion cell. The bioanalyser is fully automated using s
oftware and electronics developed ex profeso in our laboratories. The
analyser was validated off-line by measuring urea and creatinine from
discrete effluent samples from hemodialysis equipment. Results agreed
with concurrent analyses realised using hospital laboratory methods. T
here were no significant differences between the two sets of results a
t the 95% confidence level, Finally, the biparametric bioanalyser was
validated on-line by measuring creatinine and urea levels in artificia
l kidney effluents, These measurements were useful in the determinatio
n of key biochemical parameters of clinical interest such as the mass
of urea and creatinine extracted from the patient as well as the initi
al concentration of creatinine and urea in blood plasma. When the resu
lts of the bioanalyser mere compared with those yielded by the usual m
ethods, they showed no significant differences at the 95% confidence l
evel when determining the mass of the analytes extracted by the hemodi
alyser or when determining the urea concentration in blood plasma. How
ever, when measuring the creatinine concentration in blood plasma usin
g the developed bioanalyser, significant differences appeared.