Abstract
BackgroundThe accuracy and precision of liquid handling can be altered by several causes including wearing or failure of parts, and human error. The last cause is crucial since point-of-care testing (POCT) devices can be used by non-experienced users or patients themselves. Therefore it is important to improve the method of informing the users of POCT device malfunctions due to damage of parts or human error.MethodsIn this paper, image-based failure monitoring of the automated pipetting was introduced for POCT devices. An inexpensive, high-performance camera for smartphones was employed in our previous work to resolve various malfunctions such as incorrect insertion of the tip, false positioning of the tip and pump, and improper operation of the pump. The image acquired from the camera was analyzed to detect the malfunctions. In this paper, the reagent volume in the tip was estimated from the image processing to verify the pump operation. First, the color component corresponding to the reagent intrinsic color was extracted to identify the reagent area in the tip before applying the binary image processing. The extracted reagent area was projected horizontally and the support length of the projection image was calculated. As the support length was related to the reagent volume, it was referred to the volume length. The relationship between the measured volume length and the previously measured solution mass was investigated. If we can predict the mass of the solution by the volume length, we will be able to detect the pump malfunction.ResultsThe cube of the volume length obtained by the proposed image processing method showed a very linear relationship with the reagent mass in the tip injected by the pumping operation (R2 = 0.996), indicating that the volume length could be utilized to estimate the reagent volume to monitor the accuracy and precision of the pumping operation.ConclusionsAn inexpensive smartphone camera was enough to detect various malfunctions of a POCT device with pumping operation. The proposed image processing could monitor the level of inaccuracy of pumping volume in limited range. The simple image processing such as a fixed threshold and projections was employed for the cost optimization and system robustness. However it delivered the promising results because the imaging condition was highly controllable in the devices.
Highlights
The accuracy and precision of liquid handling can be altered by several causes including wearing or failure of parts, and human error
Despite the throughput might be smaller than that of a conventional system, it is relatively flexible, small, and inexpensive. Such a point-ofcare test (POCT) device performs the task of a portable clinical test while being suitable to carry out the selective diagnosis work required at small hospitals [9,10,11,12,13,14,15,16,17]
The average and standard deviation of the reagent mass for each step is shown in Table 1, where the coefficients of variation (CV) values are shown in the last row
Summary
The accuracy and precision of liquid handling can be altered by several causes including wearing or failure of parts, and human error. Small hospitals may send samples to a central laboratory equipped with the appropriate system, but this will result in patients feeling uncomfortable due to the slow turnaround time of the test results To address these problems, a portable clinical test system using robotic automation was recently developed [4]. Despite the throughput might be smaller than that of a conventional system, it is relatively flexible, small, and inexpensive Such a point-ofcare test (POCT) device performs the task of a portable clinical test while being suitable to carry out the selective diagnosis work required at small hospitals [9,10,11,12,13,14,15,16,17]. Aided by the development of lab-on-a-chip (LOC) techniques, the development of POCT devices are accelerating [10, 13,14,15, 17]
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