Low-Cost, Volume-Controlled Dipstick Urinalysis for Home-Testing

Manual performance of urinalysis dipstick relies on good technique and time-sensitive comparison to chart colors, but automating key steps, we can eliminate potential sources of error and allow home testing. So as a device, it's customizable, inexpensive to manufacture and easy to assemble. It can be used to perform automated urinalysis in any environment.

Although critical measurements in fabrication steps are necessary to ensure robust operation, the device implementation is simple and provides accurate and reliable results. After designing the device in an appropriate computer aided design software program, print the inlet cover, top plate, slide and box on a laser cutter into the urinalysis device-based plate on a 3D printer. Use sandpaper to sand the top face area of the base plate between the ledges to roughen the surface.

To assemble the inlet and top plate, use acrylic cement to glue the inlet cover onto the top plate where the inlet hole is located. Tape the ledges of the base plate with adhesive tape and holding a can of hydrophobic spray eight to 12 inches away, spray the base plate, top plate, and slide with four to eight coats. The device should have a milky white appearance upon drying.

After waiting 12 hours for the base plate to completely dry, remove the tape from the ledges. When the spray has completely dried, align the completed top plate with the ledges of the base plate and use acrylic cement to glue the two pieces together to create the plate sleeve. Then use a clamp to secure the pieces together while drying.

While the device is drying, download a QR code from an online QR code generator into the commercially printed vinyl chart sticker from the manufacturer's website. Print the desired code and chart on paper with sticky adhesive backing. Place the QR code 0.17 inches from the right of the first through hole adjacent to the row of through holes and do use clear tape to cover and secure the code to the slide.

Then place the vinyl chart sticker to the plate sleeve so that it is aligned with each through hole. To prepare the test, download the urine test mobile application from GitHub and install the app onto a mobile phone. Read the instructions and adjust the analyte names and reading times to be adjusted to match those for the dipstick of interest.

Insert the dipstick into the through holes under the plate sleeve and place the plate sleeve inside the box so that the notch is aligned with the box gap. Place the slide into the plate sleeve so that the through holes are aligned with the inlet and place the phone on the top of the box with the back camera lens facing the viewing through hole. Confirm that the phone position will allow an image of the test strip to be acquired through the camera lens and launch the urine test application.

Then align the phone so that the dipstick coincides with the boundaries of the black rectangular overlay on screen and click start to begin the test. To analyze a urine sample, use a disposable polyethylene transfer pipette to deposit approximately 500 microliters of urine into the inlet hole and push the slide into the plate sleeve until it is stopped by the base plate top to initiate the test. Here, representative results from a urinalysis test performed with a high-quality smartphone can be observed.

As expected, the color of the dipstick did not change in response to water. With the final value for the standard urine, matching with the normal urinary glucose threshold level, and the final value for the high glucose condition being elevated above the normal value. It is important to note that the correct value is not attained for 30 seconds, illustrating the importance of setting the timing readout interval correctly.

Using a smartphone with a lower image resolution and flashlight specifications, a significant reduction in the image color and quality of the dipstick panel is observed. The color matching algorithm used by the smartphone application for the urinalysis test, however, yields the same results for the analyte concentrations despite the differences in the physical appearance of the colors of the dipstick pads. Comparing the results captured by an automated urinalysis device to those obtained using the traditional dip-and-wipe method and the commercial urine standard reveals that the accuracy of the automated urinalysis device system depends on the volume transferred to each dipstick pad.

Therefore, it is critical that the device is able to accurately and consistently transfer the required urine volume to the dipstick pads. One limitation of this technique is that the hydrophobic coatings may peel with frequent use, thus altering the transferred volume and potentially reducing the accuracy. Additionally, the acrylic bonding may also weakened with repeated testing.

The protocol can be used to use with any kind of dipstick with different brands by sending the timers and adjusting the phone app. The method provides increased accuracy of results even when performed by non-trained individuals, suggesting that it as amenable to patient self-testing.