By Guido Cimoli
Brucellosis remains one of the most common zoonoses worldwide. It affects livestock producers through abortions and lost production, and it is a notifiable disease in many countries. Put those factors together and a diagnostic lab in an endemic area or supporting an eradication programme can find itself handling very large sample numbers during a screening campaign.
Many of those samples are screened using the Rose Bengal Test (RBT), a rapid serum agglutination test (also known as SAR). Buffered, stained Brucella antigen is mixed with serum, the plate is mixed and tilted and the resulting agglutination is read. The World Organization for Animal Health (WOAH) recognizes RBT for brucellosis testing and it has earned its place: it is fast, inexpensive and well suited to screening large numbers of samples.
So, if the test itself is not particularly complicated, why can it become so difficult to manage?
The problem is what happens when sample numbers increase. A simple manual assay becomes much more complicated when hundreds of samples need to be processed — particularly when the results are operator dependent.
In practice, manual RBT throughput is limited by what an operator can prepare, process and read before quality begins to slip. During a surveillance campaign or outbreak, that can become a real constraint. There is also the paper trail: when a result needs to be reviewed later, a plus or minus sign in a logbook provides relatively little evidence of what was actually observed.
This is exactly the kind of workflow where automation can make a significant difference.
Moving RBT onto a Fluent®-based system takes many of the repetitive and operator-dependent steps away from the operator. Liquid handling provides consistent pipetting. A dedicated Rose Bengal mixer keeps the antigen homogeneous. Mixing and reaction timing follow a fixed protocol rather than being performed by feel.
Figure 1: Fluent SAR Assay Prep workstation to standardize the repetitive steps.
The read can also be automated. The SciRobotics FluHema™ imaging module uses a machine-learning model trained on images of real plates to evaluate agglutination consistently, applying the same criteria to every plate regardless of who is on shift or what time it is.
Automation also addresses the record problem. An image of each plate can be stored alongside its result, providing a digital record for traceability and review without somebody having to assemble the evidence afterwards.
And then there is throughput. The automated workflow can process several hundred samples in under three hours, while providing standardized processing, full traceability and minimal operator intervention. Reusable plates and fixed tips can also help keep running costs under control at campaign volumes.
Importantly, this is walkaway time. Instead of spending those hours pipetting, mixing, reading and recording results, laboratory staff are free to focus on other tasks while the system runs.
And once the automation is there, a couple of additional capabilities are worth considering. They are not required for the RBT itself, but they can solve other problems around high-volume testing.
Cap piercing allows the system to draw serum or blood through a pierceable tube cap rather than requiring someone to manually open hundreds of primary tubes. That means less handling and and less chance of sample mix-ups. That’s particularly relevant when working with samples being tested for Brucella.
Barcode reading is another straightforward addition, keeping each result tied to its sample ID and removing a manual transcription step.
And looking further ahead, the open deck of the Fluent platform means the instrument does not have to stop at RBT. Other assays like CFT (Complement Fixation Test) can be incorporated on exactly the same platform as for RBT but other like ELISA can be incorporated as well as laboratory requirements evolve.
The Rose Bengal Test itself is simple. Running it reliably at scale is not.
Automation does not change the principle of the test. It changes how consistently, efficiently and traceably a laboratory can apply it when sample numbers start to climb.
For detailed workflow information and performance data contact our expert.
*For research use only. Not for use in diagnostic procedures.