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Abstract: TH-PO836

Plasma Calprotectin Is a Marker of Stable Remission in ANCA Vasculitis

Session Information

Category: Glomerular Diseases

  • 1202 Glomerular Diseases: Immunology and Inflammation

Authors

  • McInnis, Elizabeth A., UNC Kidney Center, Chapel Hill, North Carolina, United States
  • Hu, Yichun, UNC Kidney Center, Chapel Hill, North Carolina, United States
  • Wu, Eve, The University of North Carolina, Chapel Hill, North Carolina, United States
  • Free, Meghan E., UNC Kidney Center, Chapel Hill, North Carolina, United States
  • Hogan, Susan L., UNC Kidney Center, Chapel Hill, North Carolina, United States
  • Bunch, Donna O., UNC Kidney Center, Chapel Hill, North Carolina, United States
  • Falk, Ronald J., UNC Kidney Center, Chapel Hill, North Carolina, United States
Background

In ANCA vasculitis, an increase in serum calprotectin (S100A8/9) was implicated as a marker of relapse and inflammation, but levels did not normalize during remission. Serum may not allow sensitive measurement of S100A8/9. We sought to determine if S100A8/9 is best measured in plasma or serum and if it is a marker of disease activity and remission in ANCA vasculitis.

Methods

S100A8/9 was measured by ELISA (BioLegend) in 16 paired serum and plasma samples. Plasma levels were also tested in 31 patients during active (BVAS>3, 15 MPO, 16 PR3) and remitting disease and in 14 age/gender matched healthy subjects. Additionally, 8 patients (4 MPO, 4 PR3) in long term remission off therapy (LTROT) for ≥5 years were evaluated and compared to healthy subjects.

Results

Serum measures of S100A8/9 averaged 2.90 μg/mL higher and had a higher standard deviation than plasma measures (4.29 vs 4.02 respectively). Thus, plasma measures were used for all analyses.

Conclusion

Plasma S100A8/9 levels were elevated during active disease. Levels decreased during remission, but remained higher than in healthy controls. Patients in LTROT, however, had plasma S100A8/9 levels similar to healthy subjects.
These findings suggest S100A8/9 is elevated during active disease and decreases, but remains slightly elevated, during remission, possibly due to subclinical inflammation. Levels may continue to decrease and normalize in long term remission off therapy. Prior studies may have observed artificially elevated levels of S100A8/9 due to measurements obtained in serum rather than plasma.

Measurement of plasma S100A8/9 (ug/mL) in ANCA vasculitis patients and healthy subjects
Groups  Active DiseaseDisease RemissionHealthy SubjectsP Value
Paired Act vs Rem*
P Value
Remission vs Healthy Subjects**
All paired patientsN
Median
(IQR)
31
2.56
(1.90, 5.31)
31
1.60
(1.13, 2.00)
14
0.86
(0.77, 1.26)
<0.00010.009
MPO patientsN
Median
(IQR)
15
2.99
(1.99, 5.26)
15
1.60
(1.23,1.98)
14
0.86
(0.77, 1.26)
0.0020.005
PR3 patientsN
Median
(IQR)
16
2.54
(1.82, 6.66)
16
1.58
(0.86, 2.28)
14
0.86
(0.77, 1.26)
0.0180.085
LTROT patientsN
Median
(IQR)
 8
1.10
(0.77, 1.44)
14
0.86
(0.77, 1.26)
 0.517

*P value was calculated by signed rank paired test. ** P value was calculated by Wilcoxon two sample test.

Funding

  • NIDDK Support