Rationale: Gout is a disease with growing incidence and complexity due to increased life
expectancy, co-morbidity and medication. The disease can be diagnosed by microscopy,
demonstrating monosodium uric acid (MSU) in synovial fluid of the affected joint or in tophi
(subcutaneous or peritendinous MSU depositions). In daily practice, however, the diagnosis is
difficult to ascertain due to sampling error (no synovial fluid acquired because the needle
was not exactly placed in the affected joint, or the location of the gout might have been
extra-articular e.g. around tendons) or to a different cause of acute arthritis (e.g.
infection, reactive arthritis). Recently, Dual Energy CT scan has become available. This
technique allows the visualization and quantification of MSU. Although imaging modalities
such as DECT show promise in the classification of gout, the studies to date have been small
and have primarily involved people with established disease.
A study with cross-sectional design in which patients for whom the clinical questions "does
this patient have gout?" are referred for participation may contribute to assess the value of
DECT scan in diagnosing acute arthritis caused by gout.
Objective: Assessment of value of DECT scan in diagnosing acute arthritis, caused by gout.
Study design: Prospective Study population: Patients with acute mono or oligo arthritis
without prior diagnosis, the rheumatologist has an indication for diagnostic needle
aspiration.
Nature and extent of the burden and risks associated with participation, benefit and group
relatedness: In current daily practice, patients with acute mono- or oligo-arthritis without
prior diagnosis undergo a diagnostic aspiration of the affected joint. This can be done by
blind aspiration or ultra sound guided aspiration depending on the judgement of the
rheumatologist. The aspirated synovial fluid is then assessed by polarized microscopy to
detect MSU crystals. The diagnostic value of DECT in acute gout attacks had not yet been
established and is therefore not used in daily practice. In this study all patients undergo
DECT scan to assess the value of DECT scan in diagnosing acute arthritis caused by gout. If
the DECT scan demonstrates MSU depositions and the diagnosis of gout was not ascertained
prior to DECT scanning by MSU crystals in the synovial fluid, then additional ultrasound
guided aspiration will take place, with knowledge of DECT results, followed by repeat
microscopy