How to overcome “no intercept”
Whenever the status “No Intercept” or “infinity concentration” is displayed instead of an analyte concentration change in the quantification process can be performed.
Measured area ratio values which do not intercept with a quadratic
calibration curve, result in “No Intercept” or “infinity concentration”.
Generally, this can be considered as >ULOQ. To get value for these analytes,
the curve fit type may be switched from quadratic to linear. If several plates
are analyzed together, it is recommended to change the calibration curve of the
affected analytes to linear for all plates.
Customized quantification
Due to large concentration ranges in samples, metabolite
concentrations may be above the upper limit of quantification
(ULOQ). If a quadratic regression is used for quantification, values above the
ULOQ may cause the quantification status “no intercept”. Consequently, an adaptation
of the quantitation process may be necessary.
- Perform
the quantification according to the kit user manual. In WebIDQ go to Quantification > Validation or Results and check for which analytes
the status “no intercept” is displayed.
- Check
for which analytes the status “no intercept” is given. Check if the status “no intercept”
is given for only some or the majority of samples. If the majority of samples
is affected, set the regression that is used for quantification to linear and
exclude upper calibration standard level(s), which do not match the regression
line. Do so for all affected analytes. Please find an example below.