To identify temporal trends in the prescription of disease-modifying antirheumatic drugs (DMARDs) in patients with early rheumatoid arthritis (RA).
Using data from the Swedish RA register (n = 2,584), we analysed the proportion of RA patients prescribed DMARDs at their first consultation between 1997 and 2001. Statistical process control (SPC) was used to chart and analyse major changes in prescription behaviour, while more traditional time series analysis methods (i.e. regression) were used to corroborate the nature of any trend.
The SPC method identified an upward shift in the prescription of DMARDs in July 1998 and a change in the process by October 1998. Time series analysis confirmed an increasing trend in DMARD prescription over the period as a whole and the trend was statistically significant (p<or=0.0001). Further analysis showed that the trend was driven by a single shift in the data in July 1998 (p<or=0.0095), and once this shift was accounted for, no remaining trends within the periods (i.e. before and after the jump) could be detected (p = 0.5934 and 0.7497, respectively).
The formulation and promulgation of Swedish guidelines in 1998 may have influenced the prescription of DMARDs for this patient group. Prospectively analysing data derived from clinical registers in real time using SPC shows promise as a means to evaluate interventions designed to have an impact on a national level.