Dec 9, 2022
The Clinical Disease Activity Index (CDAI) is the first choice for assessing treatment effects
Using a broad evidence base, a team of IQWiG and external authors systematically compared tools for measuring treatment effects of disease-modifying antirheumatic drugs.
Reducing disease activity and, if possible, achieving almost complete alleviation of symptoms (remission) is the primary goal of treatment in rheumatoid arthritis. Various measurement tools are available to check how well this goal is being achieved. The most widely used is the Disease Activity Score 28 (DAS 28), which was developed in the 1990s and is recommended in clinical guidelines
Systematic comparison of measurement tools
In an article in BMC Rheumatology, a team led by Kirsten Janke and Beate Wieseler, both from the Drug Assessment Department at the Institute for Quality and Efficiency in Health Care (IQWiG), systematically compared four tools used to measure treatment effects in rheumatoid arthritis: the Disease Activity Score 28 (DAS 28), the Clinical Disease Activity Index (CDAI), the Simplified Disease Activity Index (SDAI), and the Boolean definition (remission only). For the first time, a comparison considered results from 60 clinical studies that were re-analysed and submitted by study sponsors within assessments of the benefit of drugs.
The authors' conclusion: If the DAS 28 or SDAI are used in clinical trials, the effect of certain treatments may be overestimated. In particular, drugs that affect certain blood values achieve better results with these tools, without reliably leading to noticeable symptom relief for patients. To achieve a fair comparison of different treatment options, the CDAI should therefore be the measurement tool of choice.
Establish the CDAI as the standard in clinical guidelines and systematic reviews
The IQWiG authors derive two demands from their findings: Firstly, clinical guidelines should be updated to reflect these findings, and secondly, HTA agencies and other authors of systematic reviews should use CDAI data to compare different treatment options. The authors do not accept the argument that often only DAS-28 or SDAI data are available, as they can be used to generate CDAI data.
To support further research on the topic, the authors have provided the results of the individual studies on the four measurement tools in the appendix of their article.