類風濕性因子與抗環瓜氨酸抗體應用於診斷類風濕性關節炎的表現

Diagnostic performance of tests for anti-cyclic citrullinated peptides and rheumatoid factor in rheumatoid arthritis

背景：分析類風濕因子與抗環瓜氨酸抗體用於診斷類風濕性關節炎的敏感度、特異度、陽性預測值、陰性預測值、陽性概似比以及陰性概似比。方法：我們收集於長庚醫院風濕免疫科門診就診並接受類風濕因子及抗環瓜氨酸抗體分析的244位病患，做回顧性分析。結果：於244位病患中，39位（15.2%）歸類於類風濕性關節炎組，另外205位（84.8%）病患歸類於非類風濕性關節炎組。39位類風濕性關節炎的病患中，有26位（67%）病患為類風濕因子陽性，有31位（79%）病患為抗環瓜氨酸抗體陽性。其中，在8位抗環瓜氨酸抗體陰性的類風濕性關節炎病患中，有2位（25%）是類風濕性因子陽性；在13位類風濕性因子陰性的類風濕性關節炎病患中，有7位（53.8%）是抗環瓜氨酸抗體陽性。對於診斷類風濕性關節炎來說，類風濕性因子的敏感度為67%，特異度為79%，陽性預測值為37%，陰性預測值為93%，陽性概似比為3.11，以及陰性概似比為0.42；相對來說，抗環瓜氨酸抗體的敏感度為79%，特異度為98%，陽性預測值為86%，陰性預測值為96%，陽性概似比為32.59，以及陰性概似比為0.21。當類風濕性因子或抗環瓜氨酸抗體陽性二者有一為陽性時，其敏感度上升至84.6%，而當類風濕性因子與抗環瓜氨酸抗體同時皆為陽性時，其特異度上升至98.1%。結論：類風濕性因子與抗環瓜氨酸抗體兩者為互補診斷類風濕性關節炎的工具。抗環瓜氨酸抗體相較於類風濕性因子而言，擁有較高之敏感度（79% vs. 67%）與陽性預測值（86% vs. 37%），但兩者有相似之陰性預測值（96% vs. 93%）。同時檢測類風濕性因子與抗環瓜氨酸抗體可以提高診斷類風濕性關節炎的機率，當臨床上出現類似類風濕性關節炎的症狀而類風濕性因子檢測為陰性時，此時仍然推薦檢測抗環瓜氨酸抗體。

Background: To compare the use of anti-cyclic citrullinated peptide antibodies (anti-CCPs) and rheumatoid factor (RF) in the diagnosis of rheumatoid arthritis (RA). Methods: Serum concentrations of anti-CCPs and RF were measured in 244 cases, including 39 patients with RA and 205 patients with other rheumatic diseases (non-RA). The age, sex, initial presentation, RF, anti-CCP results and the final diagnoses were recorded and analyzed. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (LR+), and negative likelihood ratio (LR-) were calculated. Results: Among all 244 patients, 39 (15.2%) were diagnosed with RA and 205 (84.8%) were diagnosed with other rheumatic diseases (non-RA). Among the RA patients, 26 (67%) tested positive for RF, and 31 (79%) tested positive for anti-CCPs. RF was positive in 2 of 8 (25%) anti-CCP-negative patients with RA, and anti-CCP was positive in 7 of 13 (53.8%) RF-negative patients with RA. In the diagnosis of RA, the sensitivity, specificity, PPV, NPV, LR+ and LR- of the RF test were 67%, 79%, 37%, 93%, 3.11, and 0.42, respectively. The corresponding data for the anti-CCP test were 79%, 98%, 86%, 96%, 32.59, and 0.21, respectively. The presence of either anti-CCPs or RF increased the sensitivity to 84.6%, and when they both were present, the specificity increased to 98.1%. Conclusion: The RF and anti-CCP tests are complementary in the diagnosis of RA, and positivity in both tests improves the detection of RA. The results of the present study show that anti-CCPs had better sensitivity (79% vs. 67%) and better PPV (86% vs. 37%) than RF for the diagnosis of RA in our population. However, these two tests had similar NPVs (96% vs. 93%). In cases presenting with clinical symptoms or signs of RA but negative RF results, screening for anti-CCPs is still warranted.