Pj. Murdock et al., A SIMPLE MONOCLONAL-ANTIBODY BASED ELISA FOR FREE PROTEIN-S - COMPARISON WITH PEG PRECIPITATION, Clinical and laboratory haematology, 19(2), 1997, pp. 111-114
A simple monoclonal antibody based ELISA for free Protein S, compatibl
e with out existing ELISA for total Protein S has been developed, and
its performance compared with the conventional PEG precipitation metho
d of free Protein S assay. The normal range (mean +/- 2 SD) was 0.19-0
.54 iu/ml free Protein S. The mean intra assay variation was 5.24% and
the mean inter assay variation was 5.50%. A total of 102 routine diag
nostic samples from patients referred for prothrombotic investigation
(six assays for each method), were assayed by PEG precipitation (mean
0.32 iu/ml, SD 10.60), and the monoclonal ELISA (mean 0.34, SD 0.9). P
aired t-test analysis of the two data sets indicated no significant di
fference between them (P < 0.001). In this sample population, there wa
s no significant difference in free Protein S values when assayed by m
onoclonal based ELISA or by PEG precipitation. The monoclonal assay ha
s proved to be reliable, accurate and precise. The monoclonal ELISA is
simpler, quicker and easier to perform in routine use. Data generated
is directly comparable to that generated by PEG precipitation. This m
ethodology would be suitable for laboratories currently measuring Prot
ein S by ELISA.