Editing ELISA (section)

===Indirect===
A fourth ELISA test does not use the traditional wells, rather leaves the antigens suspended in the test fluid.<ref>{{cite patent|country=US|number=7767404|title=Apparatus and method for single-step immunosorbent assay for single and multiple analytes|issue-date=August 3, 2010|inventor-last=Charbonnet|inventor-first=Derrick}}</ref><ref>{{cite patent|title=Systems and methods for immunosorbent assays for single and multiple analytes|country=US|number=8735142|issue-date=May 27, 2014|inventor-last=Charbonnet|inventor2-last=Evans|inventor-first=Derrick|inventor2-first=Norman Scott}}</ref>

# Unlabeled antibody is incubated in the presence of its antigen (sample)
# A sufficient incubation period is provided to allow the antibodies to bind to the antigens.
# The sample is then passed through the Scavenger container. This can be a test tube or a specifically designed flow through channel. The surface of the Scavenger container or channel has "Scavenger Antigens" bound to it. These can be identical or sufficiently similar to the primary antigens that the free antibodies will bind.
# The Scavenger container must have sufficient surface area and sufficient time to allow the Scavenger Antigens to bind to all the excess Antibodies introduced into the sample.
# The sample, that now contains the tagged and bound antibodies, is passed through a detector. This device can be a [[Flow cytometry|flow cytometer]] or other device that illuminates the tags and registers the response.<ref>{{cite journal |last1=Mahmoudi Gomari |first1=Mohammad |last2=Saraygord-Afshari |first2=Neda |last3=Farsimadan |first3=Marziye |last4=Rostami |first4=Neda |last5=Aghamiri |first5=Shahin |last6=Farajollahi |first6=Mohammad M. |title=Opportunities and challenges of the tag-assisted protein purification techniques: Applications in the pharmaceutical industry |journal=Biotechnology Advances |date=December 2020 |volume=45 |pages=107653 |doi=10.1016/j.biotechadv.2020.107653 |pmid=33157154 |s2cid=226276355 |url=https://www.sciencedirect.com/science/article/abs/pii/S0734975020301555 |language=en |issn=0734-9750}}</ref>

This test allows multiple antigens to be tagged and counted at the same time. This allows specific strains of bacteria to be identified by two (or more) different color tags. If both tags are present on a cell, then the cell is that specific strain. If only one is present, it is not.

This test is done, generally, one test at a time and cannot be done with the [[Microplate|microtiter]] plate. The equipment needed is usually less complicated and can be used in the field.