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Accurate Blood Counting Without User Training

19 Mar | By Biophotonics.World
Accurate Blood Counting Without User Training
Using microcapillaries, premixed reagents, and a mass-produced sample chamber, USTC researchers created an accurate blood counting method – no matter whether the user is trained or not. (1) Whole blood is drawn from a finger stick into a 10 µL capillary, which is then (2) dropped into a tube of premeasured reagents and (3) shaken for 10-30sec. (4) The prepared blood is then transferred to a measurement chamber using a 100 µL capillary, and (5) placed on a home-built, cost-effective automated microscope for measurement.
Image source: Journal of Biophotonics https://doi.org/10.1002/jbio.201700030.

The complete blood count (CBC) is one of the most commonly ordered clinical laboratory tests. It provides doctors with red blood cell (RBC) and white blood cell (WBC) counts, platelet counts, and hemoglobin concentration. The CBC can help diagnose blood illnesses such as anemia or leukemia, as well as help diagnose infection, internal bleeding, and other maladies. Further, because of its minimally invasive nature, it is a common starting point for a doctor to determine appropriate follow-up tests.

 

In advanced health care environments, the CBC is provided by a dedicated instrument known as an automated hematology analyzer, essentially a specialized flow cytometer that automatically prepares the blood through a combination of dilution, controlled cell lysis, and fluorescence staining, then measures the cells one-at-a-time. While these specialized systems offer unparalleled performance and speed, they are costly and require a highly skilled operator who performs routine system calibration. This places these systems out of reach of small clinics and low-resource healthcare settings. Further, these systems have poor performance on body fluids other than blood (such as cerebral spinal fluid or ascites), requiring these samples to be counted by hand even in state-of-the-art hospital settings.


Therefore, there is an urgent need for new methods of blood counting capable of being operated by untrained users, particularly as the CBC, if delivered near the point-of-need, can act as a screening step that can efficiently allocate scarce healthcare resources. To address this need, Dengling Xie and co-authors in the Multimodal Biomedical Imaging and Therapy Lab at the University of Science and Technology of China (USTC) have developed a simple, inexpensive CBC instrument capable of being operated by completely untrained users. Their results are reported in the February 2018 issue of the Journal of Biophotonics. Rather than using flow cytometry, the USTC method utilizes fluorescence and bright field imaging performed on a low-cost microscope. The images are then automatically computer-analyzed to determine cell counts, returning RBC, WBC, and platelet counts, along with a 3-part WBC differential.


Development of the method started in 2013 when study co-authors Kaiqin Chu and Zachary Smith were postdoctoral scholars at UC Davis. Early work focused on providing blood counts of cancer patients undergoing chemotherapy. As the chemotherapy drugs slowly erode the patients’ immune systems, they are at risk of internal bleeding and infection due to reduced platelet and WBC counts. Therefore, they must routinely have their blood count monitored to determine when their therapy regimen must be adjusted or paused. Thus, a portable CBC method could enable convenient home testing for therapy monitoring.


After positive results were reported in Lab on a Chip, the method was expanded to explore use in non-human mammals such as cats and dogs, as well as in human body fluids, as reported in 2015 in Analytical Chemistry. However, a key unanswered question in these earlier studies was how well the instrument and method could perform when operated by untrained users outside of a controlled laboratory setting.


To address this, the USTC group further refined their portable method to simplify the sample preparation and measurement automation. According to Xie, “Our original system required preparing the sample in a few steps, with lots of pipetting. You had to practice it a few times to really get the hang of it.” Solving this challenge required re-engineering the reagent system to allow all of the chemicals to be pre-prepared, eliminating the need for pipetting and reducing the sample preparation to a single dilution step. With a simplified preparation method in hand, the control of the microscope was also automated to the “push-button” level. Performance of the system was assessed on 120 blood samples measured by expert as well as untrained users, in both laboratory and field settings.


For each blood sample, the results of the low-cost method were compared with the clinical gold standard using the error targets laid out by the US Center for Medicare and Medicaid Services (CMS) Clinical Laboratory Improvement Amendments (CLIA) guidelines for the complete blood counts. CLIA guidelines set the maximum allowable error for laboratory tests, with the requirement that >95% of measurements must fall within these error targets.


The results of the USTC field trial demonstrated that the new, low-cost, easy-to-use method were not only statistically equivalent with the clinical gold standard, but that this performance was independent of user training. According to study co-author Zachary Smith, “This means that users who have never even seen our instrument before can walk up, read a short protocol, and get accurate results in just a few minutes.” For those living in remote rural environments, the ability to have a CBC performed at a local clinic, or even at their own home, could save a costly or time-consuming trip to the hospital and increase their access to care. 


Related journal article: https://doi.org/10.1002/jbio.201700030.


Article provided by Zachary Smith

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