The relationship between change in subjective outcome and change in disease: a potential paradox

BACKGROUND

Response shift theory suggests that improvements in health lead patients to change their internal standards and re-assess former health states as worse than initially rated when using retrospective ratings via the then-test. The predictions of response shift theory can be illustrated using prospect theory, whereby a change in current health causes a change in reference frame. Therefore, if health deteriorates, the former health state will receive a better rating, whereas if it improves, the former health state will receive a worse rating.

OBJECTIVE

To explore the predictions of response shift and prospect theory by relating subjective change to objective change.

METHODS

Baseline and 3-month follow-up data from a cohort of rheumatoid arthritis patients (N = 197) starting on TNFalpha-blocking agents were used. Objective disease change was classified according to a disease-specific clinical outcome measure (DAS28). Visual analogue scales (VAS) for general health (GH) and pain were used as self-reported measures. Three months after starting on anti-TNFalpha, patients used the then-test to re-rate their baseline health with regard to general health and pain. Differences between then-test value and baseline values were calculated and tested between improved, non-improved and deteriorated patients by the Student t-test.

RESULTS

At 3 months, 51 (25.9%) patients had good improvement in health, 83 (42.1%) had moderate improvement, and 63 (32.0%) had no improvement or deteriorated in health. All patients no matter whether they improved, did not improve, or even became worse rated their health as worse retrospectively. The difference between the then-test rating and the baseline value was similarly sized in all groups.

CONCLUSION

More positive ratings of retrospective health are independent of disease change. This suggests that patients do not necessarily change their standards in line with their disease change, and therefore it is inappropriate to use the then-test to correct for such a change. If a then-test is used to correct for shifts in internal standards, it might lead to the paradoxical result that patients who do not improve or even deteriorate increase significantly on self-reported health and pain. An alternative explanation for differences in retrospective and prospective ratings of health is the implicit theory of change which is more successful in explaining our results than prospect theory.

Methotrexate therapy in rheumatoid arthritis after failure to sulphasalazine: to switch or to add?

OBJECTIVES

MTX, either alone or in combination with SSZ, is effective in the treatment of RA. Trials have shown that, after SSZ failure, the addition of MTX to SSZ is more effective than a switch to MTX. Whether this is also the case in daily practice has not been analysed yet. In this study, we compared the efficacy of a switch to MTX monotherapy with that of the addition of MTX to SSZ in the daily clinical practice of RA patients who had failed SSZ monotherapy in the Nijmegen RA Inception Cohort.

METHODS

For this study, 230 patients who failed to SSZ monotherapy were followed for up to 52 weeks. A total of 124 underwent a switch to MTX alone, whereas 106 patients received the combination of MTX and SSZ. The primary outcome measure was the mean change in the disease activity score (DAS28) after 24 weeks.

RESULTS

Both treatment groups showed a significant decrease in DAS28 after 24 weeks, which was similar in both groups. Drug survival analysis showed that the chance to stop with a DMARD within 52 weeks was higher in the MTX-SSZ group (P <0.01).

CONCLUSIONS

In RA patients who failed to SSZ the clinical efficacy of a switch to MTX monotherapy was similar to that of the addition of MTX, suggesting that in daily clinical practice a switch to MTX is a good option for patients with an inadequate response to SSZ.

Methotrexate in combination with sulfasalazine is more effective in rheumatoid arthritis patients who failed sulfasalazine than in patients naive to both drugs

OBJECTIVES

For pharmacological reasons, the effect of the combination of MTX and SSZ may be different in RA patients who are naïve to these drugs compared to patients with an insufficient response to one of them. Therefore, we compared the results of randomized controlled trials (RCTs) on the combination of MTX and SSZ in naïve patients and in patients with an insufficient response to SSZ.

METHODS

A systematic literature search was performed to identify RCTs that compared the MTX-SSZ combination to either drug alone. The databases MEDLINE and the Cochrane Clinical Trials registry were searched from 1966 up to April 2007. The efficacy of the single therapeutic agents or their combination was assessed using the mean change in the disease activity score (DAS) and the ACR improvement criteria.

RESULTS

Four RCTs were identified to compare the efficacy of the combination MTX-SSZ to the efficacy of either drug alone. Two parallel trials were performed with patients naïve to both drugs and two add-on trials were performed in SSZ failures. In the trials with naïve patients, the mean DAS changes for the combination MTX and SSZ pointed to a sub-additive efficacy. In the trials with patients who previously failed to SSZ, the mean DAS changes for the combination MTX and SSZ indicated additive efficacy.

CONCLUSIONS

In RA, addition of MTX to SSZ is a therapeutic option in SSZ failures, whereas combination of MTX and SSZ in DMARD-naïve patients has no added value.