Subtle differences: Examining the disease activity indices used for rheumatoid arthritis

Rheumatoid arthritis (RA) is an inflammatory joint disease, which when left improperly treated could result in joint deformation and functional loss. Hence, once RA is diagnosed in an individual, appropriate monitoring and treatment are the needs of the hour.

While treating patients with debilitating diseases like RA, doctors employ several established “disease activity indices” to monitor its progression and guide treatment. Such indices yield important information about patients with RA in terms of different disease ‘grades’, ranging from mild to severe activity. However, when different indices are used for one disease, they can categorize the same patient into different disease activity groups, leading to differences in treatment. Hence, although RA diagnoses are conventionally evaluated using established indices like disease activity score 28 (DAS28), simplified disease activity index (SDAI), and clinical disease activity index (CDAI), none of these are accepted as a “gold standard”.

To understand this disparity better, a group of Chinese researchers sought to identify the correlation and concordance among the evaluated RA indices. Their pioneering study has been published in Chinese Medical Journal.

Speaking about the importance of the study, Dr. Xiao-Feng Zeng from the Department of Rheumatology, Peking Union Medical College Hospital, China, who is corresponding author of this study, says, “This is the first comprehensive comparative study of RA patients’ disease activity indices (DAIs) in China. In the future, we could accurately evaluate the epidemiology, treatment, prognosis and pharmacoeconomics of RA in China. This lays a solid foundation for the formulation of Chinese guidelines, determination of unmet clinical needs, and development of new drugs, in China.”

The researchers used information available in a big data platform for rheumatoid arthritis, called Chinese Registry of Rheumatoid Arthritis (CREDIT), from 2016 to 2018. They performed statistical analysis on the extracted data and found that of all the patients included, a staggering 80.46% were women. Further, most of the patients with RA presented with moderate-to-high disease severity.

Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are known reliable indicators of possible RA inflammation. Therefore, the researchers observed high correlations among DAS28-ESR, DAS28-CRP, SDAI, and CDAI. However, though the different indices showed high levels of correlation overall, the levels of discordance among them were also significant. Hence, the researchers concluded that there is no ‘gold standard’ index, and the indices were not interchangeable.

According to the researchers, this study will definitely pave for clinicians and researchers to perform more critical analysis of RA in patients, using the various disease indices. In this regard, Dr. Zeng adds, “Through this article, the rheumatologists will learn about the differences of RA-DAIs among the Chinese patients. At the same time, we hope that Chinese experts will join or continue to cooperate with us in providing the patient information online, thus improving the CREDIT database.”

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Reference

DOI: https://doi.org/10.1097/CM9.0000000000001517