Background Gout is a chronic, progressive, inflammatory disease characterised by elevated serum uric acid (sUA) levels. sUA levels above its saturation point result in the deposition of monosodium urate crystals, which lead to gout flares and tophi (1). Multiple studies support the use of sUA levels as a marker for clinical improvements; hence the therapeutic goal is to lower sUA levels (<6.0 mg/dL) to improve the symptoms of gout and reduce the risk of associated comorbidities (2,3).
Objectives To conduct a systematic review to identify studies reporting the effect of sUA levels on the incidence of gout flares and tophus status in adult patients with gout/hyperuricaemia, with a focus on publications reporting a correlation between the parameters.
Methods Publications were identified by interrogating electronic databases; Medline & MEDLINE In-Process, EMBASE and the Cochrane Library (accessed 6 Sept 2016). Eligibility criteria included adult patients with a diagnosis of acute/chronic gout or hyperuricemia, with no restriction on publication date, study design or geography.
Results In total, 59 studies met the pre-defined inclusion criteria and were reviewed; of these, 17 reported the relationship between sUA levels and flares (n=12) and/or tophus status (n=11). Two studies were multinational (North America), and 15 were single country (US [n=10]; Spain [n=2]; New Zealand [n=1]; Germany [n=1]; Japan [n=1]). The majority of studies had a follow-up period of ≤1 year, with one reporting 10 years' follow-up. All 12 studies evaluating flares reported that achieving sUA levels ≤6 mg/dL was associated with a decreased risk of gout flares, compared with sUA levels >6 mg/dL (p<0.05 in 8 studies). All 11 studies evaluating tophus status reported that achieving sUA levels ≤6 mg/dL was associated with improvements in tophus status, compared with sUA levels >6 mg/dL (p<0.05 in 4 studies). The remaining 42 studies reported the impact of urate lowering therapy on sUA levels and gout flares or tophus status, but not the correlation between the parameters. The qualitative results in these studies indicated that increases in sUA levels were associated with an increased risk of gout flares and worsening of tophus status.
Conclusions Maintenance of sUA levels <6 mg/dL is associated with improvements in tophi resolution and flare reduction in adult patients with gout/hyperuricaemia. Whilst longer-term follow up studies (>5 years) are warranted, this review further supports that decreases in sUA levels are a marker for clinical improvements.
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Shoji A, et al. A retrospective study of the relationship between serum urate level and recurrent attacks of gouty arthritis: evidence for reduction of recurrent gouty arthritis with antihyperuricemic therapy. Arthritis Care Res. 2004;51(3):321–5.
Disclosure of Interest S. Mitchell: None declared, L. Manounah: None declared, H. Liedgens Employee of: Grünenthal GmbH, E. Johannes Employee of: Grünenthal GmbH