Gout Activity Score has predictive validity and is sensitive to change: results from the Nottingham Gout Treatment Trial (Phase II)

An update on gout diagnosis and management for the primary care provider

Gout is the most common inflammatory arthritis in the US, affecting 3.9% of the population. Although many effective gout therapies are available for acute flares and chronic management, it is suboptimally treated worldwide, and recurrent gout flares can cause significant pain and irreversible joint damage.

Development of a multivariable improvement measure for gout

Background

Gout is a heterogeneous inflammatory disease with numerous clinical manifestations. A composite means to assess the impact of therapy on numerous aspects of gout could be useful.

Methods

Results from patients treated with pegloticase or placebo in two randomized clinical trials and their open-label extension were assessed using a novel evidence-based Gout Multivariable Improvement Measure (GMIM) derived from previously reported criteria for remission and complete response. Improvement was defined as serum urate (sU) < 6 mg/dL and absence of flares during the preceding 3 months plus 20, 50, and 70% improvement in tophus size, patient global assessment, pain, and swollen and tender joints.

Results

Patients treated with pegloticase manifested a significantly greater GMIM20, 50, and 70 response vs those treated with placebo (GMIM20 at 6 months 37.1% vs 0%, respectively). Higher response rates were significantly more frequent in subjects with persistent urate lowering (GMIM 58.1% at 6 months) in response to pegloticase versus those with only transient urate lowering (GMIM 7.1% at 6 months). However, when the requirement for a decrease in sU to < 6 mg/dL was omitted, a substantial percentage of subjects with transient urate lowering met the GMIM clinical criteria. A sensitivity analysis indicated that gout flares contributed minimally to the model. The response measured by GMIM persisted into the open-level extension for as long as 2 years. Finally, subjects who received placebo in the randomized control trials, but pegloticase in the open-label extension, manifested GMIM responses comparable to that noted with pegloticase-treated subjects in the randomized controlled trials.

Conclusions

GMIM captures changes in disease activity in response to treatment with pegloticase and may serve as an evidence-based tool for assessment of responses to other urate-lowering therapies in gout patients.

Evaluation of Proposed Criteria for Remission and Evidence-Based Development of Criteria for Complete Response in Patients With Chronic Refractory Gout

Objective

The objective of this study is to assess criteria for gout remission and to use the results to inform criteria for a complete response (CR).

Methods

A post hoc analysis of two clinical trials was undertaken to determine the frequency with which subjects with chronic refractory gout who were treated with pegloticase met remission criteria. Mixed modeling was then employed to identify the components that best correlated with time to maximum benefit.

Results

Of the 56 subjects treated with biweekly pegloticase for whom adequate data were collected, 48.2% met the remission criteria. When subjects with persistent lowering of urate levels were examined separately, 27 of 32 (84.4%) met the criteria for remission. In contrast, even when the requirement for lowering of serum urate levels was waived, only 2 of 24 (8.3%) subjects without persistent lowering of urate levels and 0 of 43 subjects receiving placebo met criteria. Mixed modeling indicated that in addition to urate levels, assessment of tophi, swollen joints, and tender joints and patient global assessment best correlated with time to maximum benefit. Using these criteria of CR, 23 of the responders (71.9%) met the criteria. All patients who achieved a CR maintained it for a mean duration of 507.4 days. Finally, 64% of persistent responders to monthly pegloticase also met criteria for CR.

Conclusion

These results have validated the proposed remission criteria for gout and have helped define criteria for CR in individuals with chronic gout treated with pegloticase. This composite CR index can serve as an evidence-based target to inform the design and end points of future clinical trials.