Biomedical Engineering Reference
In-Depth Information
populations, eight sera were tested on ANA-BA stored at 4 or 40 C, respectively,
over 8 days.
The signal cut-off of each parameter was adjusted using panel A so that at least
99% of these control samples were negative. Using these settings, 750 sera of
panel B were analyzed by ANA-BA. In addition, a subgroup of sera from this
panel was tested with commercially available IVD-CE-marked reference ELISA.
Data were processed to calculate kappa coefficient [ 39 ], relative sensitivity, and
specificity. In the case of some antigens, fine-tuning of the cut-off was done using
receiver operating characteristic analyses (data not shown) to exceed at least 95%
specificity for each parameter.
Intra-assay precision was calculated from eight parallel determinations for some
of the parameters which reacted with the sera used. The mean of the relative
fluorescence units (rfu) of these different parameters ranged between 0.01 and 2.22,
and the intra-assay precision varied between 1.8 and 6% (Table 1 ). Inter-assay
precision was calculated from determinations of three different runs using micro-
plate modules of the same batch. The mean of the rfu of these different parameters
ranged between 0.01 and 1.70, and the intra-assay precision varied between 1.8 and
12% (Table 1 ).
Inter-batch precision was determined using microplate modules of three dif-
ferent batches in parallel. The mean of the different immune reactivities ranged
between 0.01 and 2.23. The mean of all immune reactivities was 0.8. Inter-batch
precision ranged between 1.2 and 19.9%.
To demonstrate ANA-BA stability, test modules were stored at 4 C and a
second set of modules at 40 C for 1 week. Comparison of both differentially
stored sets of modules showed that all the tested parameters did not lose their
immune reactivity at higher temperatures (Fig. 12 ).
The analytical performance of ANA-BA was studied in comparison
with commercial reference ELISA using 59-400 patient sera for each parameter
(Table 2 ). The kappa coefficients are mostly above 0.8, which means ''very good''
accordance between ANA-BA and reference test results. The dsDNA and Scl-70
tests, with kappa of 0.678 and 0.668, respectively, are classified as ''good''. The
specificity of ANA-BA ranges between 96 and 100%. The sensitivity of all
parameters with the exception of dsDNA and Scl-70 is above 90%. In the cases of
RNP/Sm and Sm, sensitivity as well as specificity are both 100%.
The VideoScan application ANA-BA combines the advance of microplate
technology with a high potential for automation of test manufacturing as well as
test processing in routine laboratory workflows. In comparison with the 96-well
ELISA format, each well of the ANA-BA comprises nine AAGs as diagnostic
parameters and two integrated controls that enhance test reliability. Positive
control indicates general test function as, e.g., altered anti-IgG conjugate, or tests
inhibition if washing steps were performed inefficiently. Increased negative control
values may indicate non-specific binding of ''sticky'' serum samples. Generally,
the technology permits the determination of up to 18 AAB species so far, and
processing of several hundred samples per day.
Search WWH ::




Custom Search