# IgA autoimmunity and coagulation among post-acute sequelae of SARS-CoV-2 infection (PASC) patients with persistent respiratory symptoms: a case-control study

## TL;DR

This study explores how IgA autoimmunity and coagulation might be linked to persistent respiratory symptoms in long COVID patients.

## Contribution

The study identifies a novel inverse correlation between IgA autoimmunity and clinical symptoms in PASC patients.

## Key findings

- Clinical symptoms in PASC patients inversely correlate with plasma total IgA levels and IgA autoimmunity to lung antigens.
- Total IgA levels directly correlate with clot strength parameters like fibrinogen and fibrin.
- SPECT-CT scans showed limited perfusion differences between PASC patients and controls.

## Abstract

The SARS-CoV-2 virus resulted in significant disability and diagnostic challenges among patients with Post-Acute Sequelae of COVID-19 (PASC). Here, we assessed microvascular perfusion, clotting, and autoimmune responses to lung targets in PASC patients compared to healthy controls with the aim of explaining the persistent respiratory symptoms of patients with PASC.

We performed a blinded case-control study of 20 PASC patients with persistent respiratory symptoms versus 20 healthy controls previously infected with SARS-CoV-2 virus. We assessed lung perfusion using Technetium-99m macroaggregated albumin (MAA) SPECT-CT scans, clotting using coagulation and thromboelastrogram (TEG) tests, and autoimmunity to vascular and lung antigens using ELISA assays.

Subjective respiratory symptoms and quality-of-life measures were significantly worse among the PASC patients compared with healthy controls (p<0.001). Clinical symptoms among PASC patients were inversely correlated with plasma total IgA levels (coefficient: -0.61, p=0.004) and with autoimmune IgA recognizing pulmonary microvascular endothelial cell antigens (coefficient: -0.51, p=0.02). Additionally, levels of total IgA were directly correlated with fibrinogen and fibrin-related clot strength (coefficient: +0.52, p=0.02; coefficient: +0.63, p=0.003). SPECT-CT scans were positive only among 25% of PASC cases versus 10% of healthy controls (p=0.41). TEG tests showed no differences between the groups.

Our small study of PASC patients identified that circulating IgA antibodies may correlate inversely with clinical symptoms and directly with clotting parameters, suggesting a possible link between autoimmunity and coagulation. However, many of the study’s findings were null, which may mean that tissue-level studies or alternative explanations of PASC need to be explored.