Diagnosis
Diagnosis
The presenting symptoms of gout are usually definitive: rapid onset (often overnight) of severe pain, redness and swelling in one or more distal joints, most commonly the big toe, but sometimes the mid-foot, ankle, knee, hand, wrist or elbow.
They may also be tophi – firm white nodules under translucent skin, which are usually painless, but can become inflamed, infected or ulcerated and may exude – on the surfaces of affected joints, suggestive of long-standing and untreated gout.
A history of similar, self-limiting (seven to 14 days) attacks supports the diagnosis, as does tenderness and limited range of movement, likely to impact negatively on functioning. Dietary habits, comorbidities, risk factors and family history (of gout, hyperuricaemia or renal disease) should also be established.
In the June 2022 guidance, NICE recommends testing the serum uric acid level of someone who is exhibiting signs of gout, with 360micromol/L or 6mg/dL regarded as diagnostic. If the level during an attack is lower than this, at least two weeks should be allowed to elapse before repeating the test.
Joint aspiration and microscopy of synovial fluid should be considered if a diagnosis of gout remains uncertain or unconfirmed. If this cannot be performed, imaging techniques are regarded as a sensible way forward.
Left untreated, around 2 per cent of gout sufferers will go on to develop debilitating arthritis some two decades after their first acute episode. There are many other potential complications to motivate a swift diagnosis (although the condition is regarded as so painful, it seems unlikely someone in the throes of an attack would not seek medical advice), including joint damage, renal stones and tophi.
Reduced quality of life is also a real concern, not just from tophi – which can cause problems with daily living activities, as already mentioned, and carry with them an increased risk of secondary infections – but more broadly, as poorly controlled gout can increase work-related absence and use of healthcare services. Reduced participation in social activities can also impact negatively on mental health.
Early recognition of hyperuricaemia is also beneficial, as this state can lead to increased risk of cardiovascular disease and mortality, as well as chronic kidney disease (CKD). Estimates have put the prevalence of venous thromboembolism at 2.1 per cent, myocardial infarction at 2.8 per cent, cerebrovascular accident at 4.3 per cent, heart failure at 8.7 per cent and hypertension at 63.9 per cent. Almost a quarter of people with gout have CKD stages 3 to 5.
Diagnostic tests for gout
While gout is associated with hyperuricaemia, levels during an acute attack may be normal due to the uric acid having been deposited in the joint rather than being in the bloodstream. A more accurate picture may be gained by testing four to six weeks after the exacerbation
Fluid taken from the joint can be examined for the presence of uric acid crystals, which have a characteristic needle shape, as well as other types of deposits and signs of infection
To check for evidence of renal damage and adjust ULT dosing.
X-ray, ultrasound or dual-energy CT: Imaging the affected joint may show uric acid deposits, damage to the joint, or indicate other conditions such as osteoarthritis
Other tests may be conducted to exclude differential diagnoses, such as checking for rheumatoid factor or anti-nuclear antibodies, which are present in some arthritic conditions.
Differential diagnoses to gout
Other conditions which may have a similar presentation to gout include:
- Cellulitis: an acute bacterial infection of the skin with the infected area painful, warm, red and swollen. Blisters may form and there are often symptoms like fever, malaise, nausea and rigors
- Bursitis: inflammation of the bursa, the sac next to the joint that allows movement without friction between the skin, tendons, ligaments and bones. It is not directly in contact with the joint itself, but when inflamed can cause swelling and sometimes pain
- Haemochromatosis: can present with joint pain due to iron accumulating when it is not absorbed from the diet. Other symptoms can include fatigue, weight loss, feeling weak, and menstrual and erectile dysfunction. It is a genetic condition, so is usually diagnosed before the age at which gout first manifests
- Septic arthritis: occurs when a joint becomes infected, either directly (e.g. due to an injury or accident) or indirectly (e.g. as a complication of surgery or an infection elsewhere in the body). Those more at risk include people with rheumatoid arthritis, gonorrhoea, compromised immunity or an artificial joint, or who have recently undergone joint surgery or are injecting substance misusers. Presenting symptoms can include abrupt and severe joint pain and swelling plus systemic symptoms such as fever and malaise
- Pseudogout: involves the deposition of calcium pyrophosphate crystals in joints, most commonly the knee. A biopsy and blood tests are needed to differentiate between this and gout
- Inflammatory arthritis: an umbrella term for conditions such as rheumatoid arthritis (RA), psoriatic arthritis (PA) and ankylosing spondylitis (AS). The symptoms of these are usually sufficiently different to differentiate them from gout – RA tends to be symmetrical, PA usually has large joint and skin involvement, and AS affects the spine so patients will complain about their back and neck.