The value of plasma calprotectin as an inflammatory marker in giant cell arteritis

Abstract

Purpose

Blood tests used in workup for giant cell arteritis (GCA) have shortcomings such as lack of disease specificity. We evaluated if plasma calprotectin at first clinical presentation could predict the final clinical diagnosis of GCA as evaluated at follow-up after six months.

Design

Prospective cohort study.

Methods

Blood was drawn at presentation in consecutive patients suspected of GCA. Plasma calprotectin was measured using the Gentian GCAL® Calprotectin Reagent Kit. The final diagnosis of GCA was given at six-month follow-up.

Results

Of 110 patients reviewed, 103 were eligible for data analysis, and 76 had plasma calprotectin analysis available. Of these 76, 44 (58 %) had a final diagnosis of GCA, 31 (41 %) had no GCA, and one case (1 %) was inconclusive. Plasma median calprotectin concentration was significantly higher in those with GCA than in those without (p < 0.001). Comparing the upper reference limit of the Gentian GCAL® (≥0.970 mg/L) with the final clinical diagnosis, plasma calprotectin performed with sensitivity 67 % (95 %CI: 50–81 %) and specificity 75 % (95 %CI: 55–89 %). The area under the receiver operating characteristics curve (AUC) was 0.71 (95 %CI: 0.58–0.84). Accuracy was 70 % (95 %CI 58–81 %). Using an optimal ROC cut-off limit of 0.635 mg/L, test statistics reached sensitivity 87 % (95 %CI: 73–96 %), specificity 61 % (95 %CI: 41–79 %), AUC 0.74 (95 %CI: 0.61–0.87), and accuracy 76 % (95 %CI: 64–86 %).

Conclusions

Plasma calprotectin was elevated in cases where GCA was subsequently confirmed. The value of plasma calprotectin as an inflammatory marker in cases with suspected GCA warrants further studies.