Qiagen QIAcuity 911000 User Manual page 203

Histogram tab for absolute quantification
The Histogram tab displays graphs that visualize the fluorescence values of selected wells for the
selected target or channel. One histogram view is created for each selected target or channel. The
histograms are sorted by channel position in imaging ("Green", "Yellow", "Orange", "Red",
"Crimson"), separated by a horizontal line.
Each histogram has two axes. The x-axis represents the relative fluorescence intensity. The y-axis
represents the number of partitions having that fluorescence intensity. The values on the y-axis have
two available scales – linear and logarithmic.
To view an additional toolbar that enables actions related to the diagram, such as downloading
the plot, hold the pointer over the diagram. For more details about the toolbar, refer to section
Diagram options.
The y-axis scale can be modified using the buttons located below each graph. The buttons are
visible when you hold the pointer over a graph. To view the values on a linear scale, click lin. To
view the values on a logarithmic scale, click log10.
Furthermore, the user can change the range of the x-axis by modifying the upper value of the
fluorescence intensity on the x-axis. For this the user clicks on the right side of the x-axis which
opens a text box. This text box is used to insert the new upper range of the fluorescence intensity.
The view of the histogram is adapted accordingly. Resetting the x-axis to the default range is
provided by using the related Reset Axes icon of the tool bar.
The Threshold field shows the threshold value of the fluorescence intensity that is used to distinguish
between positive and negative calls. If only one source well is selected, the value of the threshold
is shown in the Threshold field and on the graph as a red line. If multiple source wells are defined
and their automatically calculated threshold values are different, a threshold value is initially not
shown in the histogram.
There are two ways to change the threshold. The first one involves pointing to the chart, which
triggers the appearance of a dotted line. Once the dotted line is in the appropriate spot, click the
chart. The line becomes solid, and the threshold value is updated and displayed in the Threshold
field. To change the value again using this method, click the red line and drag it to the appropriate
spot. In addition to moving the line, you can also directly edit the value in the Threshold box. To
apply the new value on that data, click Recalculate to trigger the recalculation of results.
QIAcuity User Manual 06/2022 203