Editorial

Monitoring of rheumatoid arthritis disease activity in individual patients: still a hurdle when implementing the treat-to-target principle in daily clinical practice Monitoring disease activity in individual RA patients It is generally assumed that composite measures such as the DAS assessing 28 joints [DAS28; 0.7ln(ESR) + 0.0142(VAS) + 0.555ˇ(28TJC) + 0.284ˇ(28SJC); VAS: visual analogue scale; TJC: tender joint count; SJC: swol-len joint count] have been widely validated for use in indi-vidual RA patients. This assumption is false. The DAS28 has been validated for evaluations at group level, i.e. for measuring effects in clinical trials, but not for evaluations at individual patient level, i.e. for use in clinical practice. Is this only a theoretical, methodological issue or a relevant problem for daily practice