The purpose of this study is to evaluate the role of RF, A-CCP and imaging in the diagnosis of early RA. RA is a systemic disease, mainly involving peripheral joints. If early treatment can reduce the disability rate, treatment within 3 to 6 months after the disease is the best treatment time for RA patients, so early diagnosis and treatment of RA patients can improve the patient's Quality of life(5, 7). This study found that both RF and A-CCP antibodies have good diagnostic efficacy for early RA. The sensitivity and specificity of the two can complement each other. Our results indicate that hematological indicators combined with imaging results can significantly improve the diagnostic efficacy of early RA
The results of our study found that the serum A-CCP antibody and RF levels in the early RA group were significantly higher than the control group, and the differences were statistically significant (p < 0.05). Our research results confirmed that in the process of early RA, RF and A-CCP antibody serum levels increased, RF and A-CCP antibodies are serological markers for the diagnosis of early RA. RF is located in the Fc segment of anti-human or animal IgG and is widely present in the blood and joint fluid of RA patients(9). The results of multiple studies have shown that RF has relatively high sensitivity in the early diagnosis, but its specificity is not high, and it has a certain positive rate in systemic lupus erythematosus and chronic active hepatitis, even positive persons may be present in healthy people. This study found that RF has a higher sensitivity (82%) in the diagnosis of RA, a relatively low specificity (80%), a positive predictive value of 83%, and a negative predictive value of 80%. RF is conducive to screening but not to diagnosis, and other indicators should be combined to reduce the rate of misdiagnosis.
The peptide fragments of the cyclic filament protein are A-CCP antibodies, which are mostly of IgG type(10, 11). Schellekens et al. Synthesized CCP antigen peptides. This antigen can be used to detect A-CCP antibodies in patients(12). A-CCP antibodies can appear early in the onset of RA patients, so this antibody can be used to screen early RA. The A-CCP antibody has a high specificity in the diagnosis of rheumatoid arthritis. It can be used not only for the early diagnosis of rheumatoid arthritis, but also for judging whether arthritis is invasive and providing effective guidance for clinical treatment. However, the sensitivity of A-CCP antibodies is low, and simple detection has obvious limitations. In this study, we found that the sensitivity of A-CCP antibodies was 72%, specificity was 93%, positive predictive value was 91%, and negative predictive value was 76%. Our results indicate that A-CCP antibodies can be used as complementary serological markers to improve the sensitivity and specificity of RA diagnosis.
Logistic regression model results show that the AUC of RF and A-CCP antibody combined diagnosis of RA is 0.96, which is higher than the respective AUC of RF (0.89) and A-CCP antibody (0.88). The sensitivity of the combined diagnosis is 88%, which is also higher than the respective sensitivity of RF (80%) and A-CCP antibody (72%). The specificity of the combined diagnosis was 92%, which was higher than the RF specificity (82%) and lower than the A-CCP antibody specificity (93%). The positive predictive value is 92%, and the negative predictive value is 88%. It can be seen that this combination can significantly improve the performance of diagnosing RA. The results of this study are consistent with previous studies(13–15).
The diagnosis of RA mainly depends on clinical manifestations, laboratory examination and imaging examination. Typical cases are not difficult to diagnose, but early patients and atypical cases are easy to be missed or misdiagnosed(16, 17). These patients who are easily misdiagnosed or missed should be combined with laboratory and imaging results(18–20), our result that combined diagnosis of RF, A-CCP and radiological outcome has the highest diagnostic ability for RA conforms that combined blood and imaging is an effective mode for the diagnosis of RA. However, laboratory results have not been reported to predict the imaging increased risk of RA in people with different imaging stages. This study is the first to predict the risk of RA in people with different imaging stages in laboratory results. The results (Table. 3) found that the prediction effect of RF on the early stage of RA is significantly stronger than the middle stage of RA. The prediction effect of A-CCP on the early stage of RA is slightly stronger than that on the middle stage of RA. Especially in the early stage of imaging invasion, the OR value of RF (11.49) is the highest, indicating that with the increase of RF, the imaging increased risk of RA is greater. This results are consistent with previous study(21).
A-CCP antibodies and RF are commonly used indicators for the diagnosis of rheumatoid arthritis, and each has its own advantages, but any one test has its own limitations(5, 14, 22, 23). Less sensitive in the diagnosis of rheumatoid arthritis and can increase the risk of missed diagnosis. The low specificity can increase the risk of misdiagnosis. The combined testing of various indicators can make up for the deficiencies of single index testing to a great extent, reduce the risk of missed diagnosis and misdiagnosis, and facilitate the early diagnosis of the diagnosis, so that patients can receive symptomatic treatment in a timely manner to maximize the prognosis of patients(24).