medwireNews: Serum calprotectin may be a useful biomarker for predicting the attainment of treatment targets in patients with psoriatic arthritis (PsA), researchers report.
“These findings indicate that serum [calprotectin] may be useful for rheumatologists when making personal therapeutic plans for patients with PsA,” say Zhuoli Zhang (Peking First University Hospital, Beijing, China) and colleagues.
The study results, published in Rheumatology and Therapy, showed that calprotectin levels were significantly higher in 71 patients with PsA than in 50 healthy controls, at a respective median of 3.816 versus 0.707 µg/mL.
And the researchers note that patients with moderate or high PsA disease activity had higher concentrations of calprotectin than patients who had low disease activity or were in remission.
Significant correlations were also seen between calprotectin levels and several PsA activity scores, including tender joint count, swollen joint count, and patient’s global assessment. The strongest association was with the sum of PASI plus DAPSA scores, which the researchers say suggests “serum [calprotectin] levels were more closely related to systemic inflammation rather than single involvement of joint or skin.”
They add that the disease activity measures were more strongly associated with calprotectin than with erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels.
After a year of treatment, disease activity reduced among the patients and this was paralleled by a significant decrease in serum calprotectin levels, which dropped to a median 2.052 µg/mL at 3 months, 1.681 µg/mL at 6 months, and 1.655 µg/mL at 12 months.
The proportion of patients achieving minimal disease activity (MDA) increased significantly from 29.5% at baseline to 73.2% at 12 months, while the respective rates for low disease activity (LDA) and remission increased from 53.5% to 88.7% and 23.9% to 66.1%.
Cox regression analysis, adjusting for factors such as age, sex, arthritis duration, clinical manifestations, and initiation of biologics or Janus kinase inhibitors, showed that patients with higher calprotectin levels were significantly less likely to achieve MDA and remission within a year than those with low levels. This trend was also seen for LDA but it failed to reach statistical significance. By contrast, neither ESR nor CRP significantly predicted treatment target achievement.
The researchers estimated that the PsA patients with calprotectin levels below 5.55 µg/mL relative to higher levels achieved MDA, LDA, and remission, on average, a significant 4.8, 3.0, and 5.1 months earlier, respectively.
And area under the receiver operating characteristic curve analysis indicated a significantly greater chance of achieving an ACR50 response within 6 months and 1 year if calprotectin levels declined by more than 1.76 µg/mL at 3 months and of achieving an ACR70 response within a year if they dropped by more than 3.07 µg/mL.
“Our study illustrated the potential of serum [calprotectin] in PsA as an inflammatory biomarker by revealing its ability to monitor disease and predict treatment targets,” say Zhang et al.
However, they add that it should not replace physical examination or musculoskeletal ultrasound, as these determine focal inflammation in PsA and warn that “under some circumstances, the usage of serum [calprotectin] may be limited.”
For example, they note that “the detection of serum [calprotectin] in patients with neutrocytopenia may be inaccurate to assess inflammation since neutrophils are a major source of [calprotectin],” adding that the use of coagulants could also reduce the stability of calprotectin.
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