Point of Care Testing with the I.DOT
Dr. Felicia Truckenmueller
The definition of Point of Care Testing (POCT) is ‘simple medical assays that can be performed at the bedside.’ This means medical testing is done at or near the point of care, which means the location of the patient. And if regarded in more detail, POCT also asks for as little sample handling as possible.
Carrying out a diagnostic test right beside the patient harbors many benefits, especially the improved turnaround time, as the patients and their doctors receive the results much quicker. This allows for immediate clinical treatment decisions, which can be of great importance for critical conditions.
Even though this concept is simplistic, the ability to perform these tests has not been there until major recent technological developments. To mention only a few examples only, pulse oximetry is quick, simple, and non-invasive nowadays, and can even be found in a number of smartwatches already, while in the past it required an intra-arterial needle puncture and a laboratory test. Another very prominent examples are the COVID 19 rapid antigen tests. They became possible because the lab on a chip technology has evolved and carry state-of-the-art immunological tests. Common denominators for those assays are high sensitivity, high specificity, and little required sample input.
Generally, these tests require relatively easy sample collection of the specimens to be tested, such body fluids like saliva, urine, or finger-prick blood.
But there are many more capabilities arising with the technological improvements of sample volume miniaturization, going beyond the field of immunology. Nowadays, R&D scientist are looking at carrying out whole bioassays, such as microbiological culture, PCR or ELISA workflows as a Point of Care Test.
Another hallmark of point of care testing is the frequent use of compact transportable handheld instruments, or small benchtop devices, such as the I.DOT from Dispendix. The I.DOT is a very intuitive-to-use device, which transfers liquids of the nanoliter to microliter range from a source to a destination plate. This happens in a non-contact manner, meaning without the need for pipetting tips. The technology by which the I.DOT operates, comes with an additional number of benefits. The design of the dispensing wells allows for a very low dead volume of <1 µl for water and due to the non-contact transfer, carryover and cross-contamination are abrogated. The accuracy and precision of the liquid transfers are tight and robust, therefore decreasing the statistical errors that are potentially introduced by manual pipetting. And furthermore, the I.DOT is equipped with a system called DropDetection, which allows the counting and detection of every single droplet dispensed during a complete liquid transfer step. This gives the user immediate feedback on the overall dispensing performance and the total volume transferred.
Empyema is a serious condition of a collection of pus inside a body pocket, most frequently the space between the outside of the lungs and the inside of the chest cavity. The underlying cause is an untreated bacterial infection, and this can become eventually life threatening. Overall, the incidence rate for empyema is rather rare and symptoms are not very specific. They include fever and night sweats, lack of energy and difficulty breathing. Also, treatment options are rather limited to the dosage of antibiotics or eventually invasive measures like chest drain or a stoma.
To fill the diagnostic and pharmacological treatment gap, researchers around Andrey Komissarov and Rebekah Emerine, researchers from the Department of Cellular and Molecular Biology of the University of Texas Health Science Center at Tyler, TX have started to develop a point of care test to measure a parameter called fibrinolytic potential. This can be used as a biomarker with inter-individual ranges of two orders of magnitude. The height of fibrinolytic potential can be indicative whether a patient could be responsive to a fibrinolytic therapy, which is a less invasive treatment method for empyema than surgical interventions. But only patients with high fibrinolytic potential would benefit from the therapy, therefore an assessment shortly after the diagnosis of empyema would be beneficial to determine the subsequent treatment regime.
To develop the Point of Care (POC) Test, the researchers were able to create a fluorescent fibrin film along the perimeter of a 96-well plate in the shape of a ‘halo’. Upon successful initiation of fibrinolysis, the fluorescent reporter substrate was released into the whole well volume, which created a significant increase in overall fluorescence. The halo creation in the 96-well plates was compared if performed manually or with the I.DOT and it was found that the manual creation takes over 24 minutes, compared to only 6 minutes with the I.DOT, resulting in significant time-reduction. Further reproducibility studies showed no statistical difference in between the experiments, therefore proving the robustness of the fibrin deposition by the I.DOT. Overall, the researchers were able to create consistent fibrin halos, as well as proving that they can undergo fibrinolysis. Further they found that the preparation of the fibrin plates was an order of magnitude faster with the non-contact liquid handler I.DOT and it will be used to optimize the development of this new point of care test for fibrinolytic potential in a clinical setting.
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