Table 1.
Comparison for the design requirements and operational demands of a POC monitoring device based on World Health Organization (WHO) Standards for POC healthcare delivery at resource-scarce settings, and conventional devices at developed world settings.
Figure 1.
Depiction of the working principle of CD4+ T-lymphocyte counting microchip platform for the POC.
(a) Shadow images of captured cells were obtained using a large area CCD image sensor (24×34 mm, 10 mega pixel). A pinhole LED (Light Emitting Diode) was used as a light source. The POC platform has following two main processes. First, a microfluidic chip captured target CD4+ cells from unprocessed fingerprick volume of HIV-infected whole blood by anti-CD4 antibody which was immobilized on the microchip surface. Second, the captured cells were imaged using the wide field of view (FOV) lensless CCD platform within a second. White light generated from LED light source went through a 100 µm pinhole and illuminated captured cells. Cell shadows were automatically detected and rapidly counted by automated image recognition software on a portable laptop computer. (b) Schematic representation and drawing of the lensless imaging system for microfluidic CD4 count, (c) Photograph of entire POCT CD4 imaging system, (d) microfluidic CD4 chip on top of CCD sensor inside a black box, (e) lensless imaging and magnified image represents the diffracted shadow signal of the cell shape. Scale bar is 200 µm. Entire platform setup and operational details were shown in Text S1.
Figure 2.
Overview of Microfluidic CD4 counting chip preparation, blood injection, and lensless imaging procedures by minimally trained personnel at MUHAS.
(a) Unpacking of the microfluidic chips, (b) antibody injection, (c) one step blood injection, (d) microfluidic CD4 count chip imaging using a point-of-care portable, battery operated lensless CCD based imaging platform.
Figure 3.
The typical output of automatic CD4 cell counting program based on pattern matching.
(a) library images of cell types (a total 50 different images), (b) matching values compare an obtained shadow image and cell library images, (c) result of cell shadow image recognition using four different types of library cell patterns. The detected cells were marked with color coding to each library image that they were best matched using standard pattern recognition matching methods in MATLAB.
Figure 4.
Comparison of microchip and Fluorescent Activated Cell Sorting (FACS) CD4+ T-lymphocyte counts for HIV-infected patient whole blood samples.
The measurements were performed at BWH (Brigham and Women's Hospital, Boston, MA) and MUHAS (Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania). FACSCalibur counts were used as the gold standard to compare and validate the microchip counts. (a) Microchip measurements highly correlated with FACSCalibur measurements when conducted at an established hospital setting at BWH (y = 0.86x+304, correlation coefficient: 0.94, p<0.01). (b) When the microchips were shipped to Tanzania and the measurements were performed at MUHAS, a correlation between the microchip CD4 counts and the FACS counts were observed (y = 0.61x+312, correlation coefficient: 0.49, p<0.01). (c) Bland-Altman Analysis between the microchip and FACS counts did not display an evidence for a systematic bias for BWH measurements. The mean bias was +76 cells per µL of blood in microchip counts compared to FACS counts at BWH. (d) Bland-Altman Analysis showed a bias towards higher measurements in MUHAS results, while the mean bias was as low as +23 cells per µL of blood in microchip counts compared to FACS counts.