Background/Purpose:

Treat-to-target is the recommended strategy for the appropriate management of Rheumatoid arthritis (RA) which involves regular assessment and monitoring of disease activity using a validated measure. Currently 6 measures are recommended by the American College of Rheumatology (ACR) for use in clinical practice.

1.      Clinical Disease Activity Index (CDAI)

2.      Disease activity Score with 28 Joint Counts (DAS 28)

3.      Patient Activity scale (PAS)

4.      Patient Activity Scale II (PAS II)

5.      Routine Assessment of Patient Index Data- 3 measures (RAPID–3)

6.      Simplified Disease Activity Index (SDAI).

The table lists the key features of each:

Methods:

50 patients diagnosed with RA based on ACR/EULAR 2010 criteria were consented and asked to fill a questionnaire during that visit and follow up visits making a total of 100 encounters. The questionnaire included questions for the Health Assessment Questionnaire (HAQ), HAQ II and the Multidimensional Health Assessment Questionnaire (MDHAQ) along with the patient global Assessment. The treating physician filled out the Provider Global Assessment (0 – 10), 28 joint count for swollen and tender joints and documented their clinical impression (1 – stable, 2- mild flare, 3- moderate flare or 4- severe flare). The Disease activity measures were calculated using the ACR calculator and recorded ( 1- remission, 2- Low disease activity, 3- Moderate disease activity and 4- high disease activity). The Pearson correlation coefficient was calculated for each of the six markers compared to the physician’s clinical impression.

Results:

Patient characteristics

The best correlation was found to be with CDAI (0.84), followed by DAS 28 CRP and SDAI (0.79), then PAS (0.53), PAS II (0.47) and finally RAPID-3 (0.39).

Conclusion:

The PAS, PAS II and RAPID-3 which are patient reported are not very well correlated possibly due to over-estimation of symptoms by patients for various reasons. The dependence of SDAI and DAS-28 on CRP value makes them slightly less favorable in practice since the lab value may be reported after the patient encounter has been completed, thus making it less efficient to calculate, document and utilize. CDAI is the best correlated and due to the fact that it does not require any lab evaluation, it is evidently the best measure to adopt.