2.3. Statistical analysis
All statistical analyses were conducted with SPSS version 23.0 (SPSS Inc., Chicago, Illinois, USA) software. Numerical data were compared with an independent sample t -test or the Mann–Whitney–Wilcoxon test. Categorical data were compared with the Chi-square test or Fisher’s exact test. Spearman’s nonparametric correlation test was applied to examine the associations between serum C1q levels and Kerr’s score/ESR/hs-CRP. We selected the cutoff values for serum C1q, ESR, hs-CRP and the combination of three indicators (C1q, ESR and hs-CRP) using receiver operating characteristic (ROC) curves with MedCalc software (v.15.2) to compare the accuracies of these markers with disease activity identification. The cutoff points of these markers were the values with the highest Youden’s Index (sensitivity+specificity-1) score. A p -value less than 0.05 was considered to be statistically significant.
3. RESULTS
Of the 190 TA patients, 178were female, and 47patients had active disease based on the NIH criteria (Table 1). In addition, 29 of the TA patients in our study were naïve to corticosteroid or immunosuppressant treatment. Malaise (71.1%), headache (47.9%) and chest distress (27.4%) were the three most common constitutional symptoms, and Numano subtype V was common among the TA patients. The prevalence of claudication differed between the TA patients with active and stable disease (p =0.018). Four of the patients with active disease had Numano subtype IIa, whereas no Numano IIa cases were in clinical remission (p =0.003), Furthermore, the prevalence of hypertension was notable between untreated TA patients and treated patients (p =0.003).
Compared with the healthy controls, patients with TA had higher ESR and C1q levels (Table 1, Figure 1). However, the level of hs-CRP was similar between the TA patients and healthy controls. Compared with patients who had inactive disease, those with active disease had higher levels of serum C1q and hs-CRP as well as ESR (Table 1, Figure 1). Similarly, treatment-naïve patients had higher serumC1q, ESR and hs-CRP than those who had always been treated with corticosteroids or at least one immunosuppressant (Table 1, Figure 1). We further analyzed the relationship between serum C1qand Kerr’s score/ESR/hs-CRP with the Spearman correlation test and found that in our TA patients, serum C1q levels correlated significantly with Kerr’s score, ESR and hs-CRP (Table 2).
The areas under the ROC curve (AUCs) for C1q, ESR and hs-CRP were 0.752, 0.825, and 0.834, respectively, though without significant differences (Table 3, Figure 2). Nevertheless, when the three indicators (C1q, ESR and hs-CRP) were combined, the AUC increased to 0.845. At the same time, the AUCs between the combination of the three indicators (C1q, ESR and hs-CRP) and hs-CRP with C1q were significantly different from each other. A serum cutoff value of 167.15 mg/L C1q maximized the disease activity assessment capacity, with a sensitivity/specificity of 77.80%/64.90%. Using the established ESR and hs-CRP thresholds of our center, ESR and hs-CRP were able to identify disease activity with a sensitivity/specificity of 80.00%/81.70% and 70.20%/86.50%, respectively, and the sensitivity increased to 85.10% when the three indicators (C1q, ESR and hs-CRP) were combined (Table 3, Figure 2).