A paper recently published in Lab on a Chip by researchers from Harvard Medical School describes a new technique to read ELISA results with a cell phone camera — In their study, an ovarian cancer biomarker, HE4, was used.
There has been prior data showing that HE4 used with the traditional gold standard biomarker CA125 has improved the overall sensitivity of ovarian cancer diagnosis. (Note, CA 125 is not an effective method of screening for early stage ovarian cancer because its sensitivity isn’t high enough)
Enzyme-linked immunosorbent assay (ELISA), also known as an enzyme immunoassay (EIA), is a biochemical technique used mainly in immunology to detect the presence of an antibody or an antigen in a given sample. The test is used for a variety of disease pathologies, playing a critical role in HIV testing, due to the tests high sensitivity.
In simple terms, in ELISA, an unknown amount of antigen is bound to a surface, and then a specific antibody is applied over that surface in order to bind to the antigen. This antibody is then linked to an enzyme, and in the final step a substance is added that the enzyme can convert to some detectable signal, most commonly a color change in a chemical substrate.
The color change detection is where a smart phone was utilized in the Harvard study.
This new ELISA readout method could bring diagnostics closer to the point of patient care. It could be used in various resource-limited settings (one of the inspirations for the study) since the actual hardware requirements are minimal and clinical data can be easily transferred to other physicians and their colleagues.
“The investigators tested their readout system on an ovarian cancer biomarker HE4. A few drops of urine were loaded on a small microchip which contained polyclonal immobilized capturing antibodies. The HE4 peptide was detected using a sandwich ELISA with a horseradish peroxidase (HRP) labeled secondary antibody. Tetramethylbenzidine (TMB) is added to the chip as a reagent, and it turns blue when it is catalyzed with the paroxidase. The blue color can be measured and correlated with the HE4 concentration in the sample.”
Additionally, interpreting results can be done using a mobile app:
“To measure the color intensities of red, green and blue pixels, a customized MATLAB algorithm was developed and integrated in a mobile app. The app can take pictures for processing, select regions for analysis, calculate a standard curve and, of course, report the HE4 concentration in the patient sample. ”
Overall results are promising, paving the way for improved diagnostics, treatment and patient monitoring.
“ELISA coupled with a cell phone running an automated analysis mobile application had a sensitivity of 89.5% at a specificity of 90%. Under the same specificity, the microchip ELISA coupled with a CCD had a sensitivity of 84.2%. In conclusion, integration of microchip ELISA with cell phone/CCD-based colorimetric measurement technology can be used to detect HE4 biomarker at the point-of-care (POC).”
To read the original journal article from RSC Publishing, please click here.
Original Source: MedGadget
Cory Schultz contributed to this piece