5.2 Application Example: Automation of a Direct
Bilirubin Test
5.2.1 Direct Bilirubin
Direct bilirubin is a measurement of bilirubin which is water soluble and that has
been metabolised by the liver for excretion. A decrease in the production of direct
bilirubin in conjunction with raised total bilirubin indicates an inherited inability to
metabolise bilirubin. Raised direct bilirubin can indicate blockage of the organs of
the body which make, store and secrete bile. Here we demonstrate how a standard
hospital direct bilirubin test (Randox Laboratories BR411) might be automated on a
Lab on a Disc system.
5.3 Liquid Handling Protocol: Disc Architecture
The (typical) liquid handling protocol in Fig.5.9requires a blood sample to be
separated into its different fractions by centrifugation. Once plasma has been
Fig. 5.9 Filtering the Camera Signal (a) shows the filtering of the signal using a camera with a
‘camera ready out’(red line). When the camera is ready this signal line drops. When both this
signal and the motor signal are low the filter allows the pulses from the motor to pass through to the
camera. Note that when the camera receives a signal it will go into a non-ready state and the
subsequent pulses from the motor will be blocked. (b) shows the filtering of the signal using a
camera and a timer (red line). When the timer elapses the signal goes low. When both this signal
and the motor signal are low the filter allows the pulses from the motor to pass through to the
camera. Note that the timer should be configured such that, when a pulse is passed to the camera,
the timer resets and blocks subsequent pulses for the defined time
130 B. Henderson et al.