Post-acute infection syndromes (PAIS) may develop after acute viral disease1. Infection with SARS-CoV-2 can result in the development of a PAIS known as “Long COVID” (LC). Individuals with LC frequently report unremitting fatigue, post-exertional malaise, and a variety of cognitive and autonomic dys...
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I'm not an expert but I feel for you and will try my TLDR.
They did a study of almost 300 people. They split these into two groups, some with long COVID and some without.
They then tried to determine if those with long COVID had a signature in their antibodies. That's what "immuno phenotyping" means ... finding a unique pattern in antibody types and responses.
They did indeed find those signatures or patterns. Specifically, people with long COVID had more of specific types of antibodies and faster antibody responses to COVID and other viruses like Epstein Barr.
These differences between these two groups might help to identify and diagnose long COVID.
Further study is recommended (edit: almost all papers end with this recommendation)