Serum Calprotectin Discriminates Subclinical Disease Activity from Ultrasound-Defined Remission in Patients with Rheumatoid Arthritis in Clinical Remission.
OBJECTIVE
Clinical remission in some patients with rheumatoid arthritis (RA) may be associated with ongoing synovial inflammation that is not always detectable on clinical examination or reflected by laboratory tests but can be visualized by musculoskeletal ultrasound. The goal of our study was to determine the levels of serum calprotectin, a major leukocyte protein, in patients with RA in clinical remission and to investigate the ability of serum calprotectin levels to distinguish patients in ultrasound-defined remission from those with residual ultrasound subclinical inflammation.


METHODS
Seventy RA patients in clinical remission underwent clinical and ultrasound examination. Ultrasound examination was performed according to the German US7 score. Ultrasound remission was defined as grey scale (GS) range 0-1 and power Doppler (PD) range 0. The levels of serum calprotectin and C-reactive protein (CRP) were determined. The discriminatory capacity of calprotectin and CRP in detecting residual ultrasound inflammation was assessed using ROC curves.


RESULTS
The total number of patients fulfilling the DAS28-ESR, DAS28-CRP, SDAI and CDAI remission criteria was 58, 67, 32 and 31, respectively. Residual synovial inflammation was found in 58-67% of the patients who fulfilled at least one set of clinical remission criteria. Calprotectin levels were significantly higher in patients with residual synovial inflammation than in those with ultrasound-defined remission (mean 2.5±1.3 vs. 1.7±0.8 μg/mL, p<0.005). Using ultrasound-defined remission criteria, calprotectin had an AUC of 0.692, p<0.05 using DAS28-ESR remission criteria and an AUC of 0.712, p<0.005 using DAS28-CRP remission criteria. Calprotectin correctly distinguished ultrasound remission from subclinical activity in 70% of patients. CRP (AUC DAS28-ESR = 0.494, p = NS; AUC DAS28-CRP = 0.498, p = NS) had lower and insignificant discriminatory capacity.


CONCLUSIONS
The present study demonstrates the potential of calprotectin to distinguish RA patients in both clinical and ultrasound-defined remission from patients in clinical remission but with residual subclinical disease activity.
Institute of Rheumatology, Prague, Czech Republic.|Rheumatology Department, First Faculty of Medicine, Charles University, Prague, Czech Republic.
Jana
http://orcid.org/0000-0002-1139-539X
J
Hurnakova
Institute of Rheumatology, Prague, Czech Republic.|Rheumatology Department, First Faculty of Medicine, Charles University, Prague, Czech Republic.
Hana
H
Hulejova
Institute of Rheumatology, Prague, Czech Republic.|Rheumatology Department, First Faculty of Medicine, Charles University, Prague, Czech Republic.
Jakub
J
Zavada
Department of Methodology, Faculty of Physical Education and Sport, Charles University, Prague, Czech Republic.
Martin
M
Komarc
Institute of Rheumatology, Prague, Czech Republic.|Rheumatology Department, First Faculty of Medicine, Charles University, Prague, Czech Republic.
Petra
P
Hanova
Institute of Rheumatology, Prague, Czech Republic.|Rheumatology Department, First Faculty of Medicine, Charles University, Prague, Czech Republic.
Martin
M
Klein
Institute of Rheumatology, Prague, Czech Republic.|Rheumatology Department, First Faculty of Medicine, Charles University, Prague, Czech Republic.
Herman
H
Mann
Institute of Rheumatology, Prague, Czech Republic.|Rheumatology Department, First Faculty of Medicine, Charles University, Prague, Czech Republic.
Olga
O
Sleglova
Institute of Rheumatology, Prague, Czech Republic.|Rheumatology Department, First Faculty of Medicine, Charles University, Prague, Czech Republic.
Marta
M
Olejarova
Institute of Rheumatology, Prague, Czech Republic.|Rheumatology Department, First Faculty of Medicine, Charles University, Prague, Czech Republic.
Sarka
S
Forejtova
Institute of Rheumatology, Prague, Czech Republic.|Rheumatology Department, First Faculty of Medicine, Charles University, Prague, Czech Republic.
Olga
O
Ruzickova
Institute of Rheumatology, Prague, Czech Republic.|Rheumatology Department, First Faculty of Medicine, Charles University, Prague, Czech Republic.
Jiri
J
Vencovsky
Institute of Rheumatology, Prague, Czech Republic.|Rheumatology Department, First Faculty of Medicine, Charles University, Prague, Czech Republic.
Karel
K
Pavelka
Institute of Rheumatology, Prague, Czech Republic.|Rheumatology Department, First Faculty of Medicine, Charles University, Prague, Czech Republic.
Ladislav
L
Senolt
D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000097:blood* / Q000000981:diagnostic imaging*; D002097:C-Reactive Protein / Q000032:analysis; D005260:Female; D006801:Humans; D007249:Inflammation / Q000097:blood / Q000000981:diagnostic imaging; D039841:Leukocyte L1 Antigen Complex / Q000097:blood*; D008297:Male; D008875:Middle Aged; D018365:Neoplasm, Residual; D014463:Ultrasonography
D039841:Leukocyte L1 Antigen Complex; D002097:C-Reactive Protein