Automated pipette failure monitoring using image processing for point-of-care testing devices.

BACKGROUND: The 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. METHODS: In 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. RESULTS: The 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. CONCLUSIONS: An 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.

Evaluation of fluorescence hs-CRP immunoassay for point-of-care testing.

BACKGROUND: C-reactive protein (CRP) is one of acute phase respondents that has been used to monitor infection and inflammation episodes. Recent studies have shown that high-sensitivity C-reactive protein (hs-CRP) is a potential risk predictor for future atherosclerosis and cardiovascular diseases (CVD). METHODS: We previously developed a fluorescence-based immunochromatographic method for measuring hs-CRP concentrations (i-CHROMAtrade mark hs-CRP assay) in blood. Whole blood was mixed with detector buffer, and then loaded onto a test cartridge. After 10 min of incubation, the test cartridge was inserted and scanned for acquisition of fluorescence intensity in a laser fluorescence reader (i-CHROMAtrade mark reader). The fluorescence intensity was microprocessed and converted into the concentration of CRP in blood. The test result of 150 samples by the i-CHROMAtrade mark hs-CRP assay method was compared and evaluated with those by TBA 200FR turbidimetry and BN II nephelometry method. The Deming regression and the Bland-Altman difference plot analysis were used for comparison of hs-CRP test result. RESULTS: The i-CHROMAtrade mark hs-CRP assay system exhibited a good linearity with in the whole measuring range (R=0.997). The imprecision of intra- and the inter-assay CVs (coefficient of variation) of assay system were CVs< 3% and < 5% in the range of 0.5-20 mg/l, respectively. The i-CHROMAtrade mark hs-CRP assay method correlated well with TBA 200FR turbidimetry and BN II nephelometry assay method (R=0.988, N=143 and R=0.989, N=143). CONCLUSION: The i-CHROMAtrade mark hs-CRP assay system is comparable to those of other well-known fully automated hs-CRP assay and is suitable for point-of-care testing (POCT) in detection and quantification of hs-CRP.

Development of a point-of-care assay system for high-sensitivity C-reactive protein in whole blood.

BACKGROUND: C-reactive protein (CRP) is emerging as a potential risk predictor for future cardiovascular diseases (CVD). High sensitivity assays have been developed and applied for clinical purposes. METHODS: The fluorescence immunochromatographic assay was employed to detect and quantify CRP in whole blood. It consisted of a fluorescence (FL) antibody detector buffer, a test strip housed in a disposable cartridge, and a laser fluorescence scanner. Whole blood sample was mixed with detector, loaded onto a cartridge, incubated for 10 min, and the concentration of CRP was measured in a laser fluorescence scanner. The linearity, limit of detection (LOD), and performance of new assay system was tested and evaluated. The comparability of assay was examined with an automated reference method. RESULTS: With the new assay system, a reliable correlation of coefficient (r) was obtained between the ratio value (A(T)/A(C)) and a concentration of CRP in samples. The linearity fell in the range of 0-10 mg/l of CRP, and the analytical detection limit was 0.133 mg/l of CRP. The mean recovery of the control was 105.2% in a working range. The precision of the intra- and inter-assay in a range of 0.5-6 mg/l was CVs <6% and <8%, respectively. The new fluorescence immunochromatographic assay system correlated well with a traditional immunoturbidimetric assay for quantification of CRP concentration (r=0.955, N=90). CONCLUSION: The fluorescence immunochromatographic assay is fast, reliable, and a reproducible platform for point-of-care testing (POCT) of high-sensitive (hs)-CRP in whole blood.