Bio-Rad Rat Diabetes Assays - Manual (Page 41)

39
Possible Solutions
Pipet carefully when adding
standards, samples, detection antibodies,
and streptavidin-PE, especially when using
a multichannel pipet. Use a calibrated pipet.
Change pipet tip after every volume transfer.
If samples contain little or no analyte, negative
values observed may be due to statistical
variation. If assay drift is suspected, retest
the samples by positioning them next to the
standards. If contamination of standards
is suspected, check the standard replicate
value and be careful when adding samples to
the wells. Matrix effects could also produce
negative sample values.
Bio-Plex Manager ™ software automatically
subtracts the blank (B) FI value from all other
assay wells. While this has no impact on
observed concentrations of samples within the
assay working range, it may result in a negative
FI value if the blank’s FI value is greater than
either the standard or sample value. If this is
undesirable, then assign wells as a sample (X) or
control (C) in the protocol or results file.
Check if any interfering components such as
heparin-based anticoagulant, additives, or
gel from separators were introduced into the
samples. Avoid using hemolyzed and heavily
lipemic samples. Remove visible particulate
in samples by centrifugation. Avoid multiple
freeze/thaw cycles of samples.
Possible Causes
Poor Recovery
Improper pipetting
technique
Impact of Sample Matrix
Negative MFI values in
samples or standards
Poor precision in serum
and plasma sample
measurements