Markers for Giant Cell Arteritis and Polymyalgia Rheumatica
Markers for Giant Cell Arteritis and Polymyalgia Rheumatica
In a prospective study, 24 patients with newly diagnosed GCA (n = 12) or PMR (n = 12) were enrolled (supplementary Table S1 http://rheumatology.oxfordjournals.org/content/54/8/1397/suppl/DC1, available at Rheumatology Online). None of these patients received CSs or DMARDs at the time of blood withdrawal. GCA patients fulfilled the ACR criteria and PMR patients the Chuang/Hunder criteria. An 18F-fluorodeoxyglucose-PET/CT scan with similar or enhanced glucose uptake by large vessels in comparison with the liver was considered equal as a diagnostic criterion to a positive temporal artery biopsy. Follow-up samples were obtained from 14 patients with GCA (n = 7) or PMR (n = 7) who were in remission after 3 months of CS treatment. Remission was defined as absence of symptoms and a normal ESR (<30 mm/h). Control samples were collected from 13 age-matched healthy individuals. All procedures were in compliance with the Declaration of Helsinki. Written informed consent was obtained from all study participants, and the study was approved by the medical ethics committee of the University Medical Center Groningen (UMCG).
Serum samples were stored at −40°C and used for analysis immediately after thawing. Serum B-cell activating factor (BAFF) was measured with an ELISA kit from R&D systems. The other 25 serum markers were measured with the 25-plex Human Cytokine 25-plex (Life Technologies). The limits of detection of all measurements are provided in supplementary Table S2 http://rheumatology.oxfordjournals.org/content/54/8/1397/suppl/DC1, available at Rheumatology Online. All procedures were performed according to the manufacturer's instructions.
The Mann–Whitney U-test was used to compare serum markers between groups. The Wilcoxon Signed Rank test was used to compare serum markers within groups over time. Receiver operating characteristic (ROC) analysis with area under the curve (AUC) was performed for non-paired samples only, i.e. patients vs healthy controls. Optimal cut-off points were identified by assessing the maximum of the sum of sensitivity and specificity, according to the Youden Index. Correlations were determined with Spearman's rho correlation coefficient. Two-tailed P-values <0.05 were considered statistically significant. Statistics were performed in IBM SPSS Statistics 20 and Graphpad Prism 5.0.
Methods
Study Population
In a prospective study, 24 patients with newly diagnosed GCA (n = 12) or PMR (n = 12) were enrolled (supplementary Table S1 http://rheumatology.oxfordjournals.org/content/54/8/1397/suppl/DC1, available at Rheumatology Online). None of these patients received CSs or DMARDs at the time of blood withdrawal. GCA patients fulfilled the ACR criteria and PMR patients the Chuang/Hunder criteria. An 18F-fluorodeoxyglucose-PET/CT scan with similar or enhanced glucose uptake by large vessels in comparison with the liver was considered equal as a diagnostic criterion to a positive temporal artery biopsy. Follow-up samples were obtained from 14 patients with GCA (n = 7) or PMR (n = 7) who were in remission after 3 months of CS treatment. Remission was defined as absence of symptoms and a normal ESR (<30 mm/h). Control samples were collected from 13 age-matched healthy individuals. All procedures were in compliance with the Declaration of Helsinki. Written informed consent was obtained from all study participants, and the study was approved by the medical ethics committee of the University Medical Center Groningen (UMCG).
Measurement of Serum Markers
Serum samples were stored at −40°C and used for analysis immediately after thawing. Serum B-cell activating factor (BAFF) was measured with an ELISA kit from R&D systems. The other 25 serum markers were measured with the 25-plex Human Cytokine 25-plex (Life Technologies). The limits of detection of all measurements are provided in supplementary Table S2 http://rheumatology.oxfordjournals.org/content/54/8/1397/suppl/DC1, available at Rheumatology Online. All procedures were performed according to the manufacturer's instructions.
Statistical Analysis
The Mann–Whitney U-test was used to compare serum markers between groups. The Wilcoxon Signed Rank test was used to compare serum markers within groups over time. Receiver operating characteristic (ROC) analysis with area under the curve (AUC) was performed for non-paired samples only, i.e. patients vs healthy controls. Optimal cut-off points were identified by assessing the maximum of the sum of sensitivity and specificity, according to the Youden Index. Correlations were determined with Spearman's rho correlation coefficient. Two-tailed P-values <0.05 were considered statistically significant. Statistics were performed in IBM SPSS Statistics 20 and Graphpad Prism 5.0.
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