Gout diagnosis: Raman sheds light

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  • Published: Dec 1, 2014
  • Author: David Bradley
  • Channels: Raman
thumbnail image: Gout diagnosis: Raman sheds light

Crystalline pain

Thumbnail uric acid crystals: Wikimedia, User:Bobjgalindo. Raman spectroscopy could be used at point of care to reduce the need for inpatient admission in people with gout or pseudogout, according to results presented to the American College of Rheumatology Annual Meeting in Boston in November.

Raman spectroscopy could be used at point of care to reduce the need for inpatient admission in people with gout or pseudogout, according to results presented to the American College of Rheumatology Annual Meeting in Boston in November.

Gout is an excruciatingly painful form of acute inflammatory arthritis  caused by higher than normal levels in the blood of the metabolic waste  product uric acid precipitate our of the blood, uric acid is formed in the break down of the DNA base purine.  Needle-shaped crystals of uric acid are deposited in joints, tendons,  and surrounding tissues, the condition is often associated with pain in  the metatarsal-phalangeal joint at the base of the big toe, (when the  condition is also known as podagra). It can cause recurrent painful  attacks leading to pain and swelling in any joint, which then become  red, inflamed and hot. Half of gout cases present with big toe pain, but  gout can also cause kidney stones or urate kidney damage (nephropathy)  or tophi, large deposits of monosodium urate crystals that can even  break through the skin.

Metabolic risk

Between one and two percent of people in the developed world will suffer  from gout at some point in their lives with the increased prevalence of  metabolic syndrome being a risk factor that is on the rise for the  condition. Contrary to the deceived wisdom, gout is not caused  specifically by eating too much cheese and drinking port wine, dietary  causes account for only around one in every eight or nine cases of gout though can exacerbate gout in those with already high uric acid.  In those cases, there is, however, a strong association with drinking  alcohol, drinks containing high concentrations of the fruit sugar  fructose, meat and seafood.

Probable gout or pseudogout is usually diagnosed based on symptoms and medical inspection but  must be confirmed by testing joint fluid for monosodium urate (MSU)  crystals or calcium pyrophosphate dihydrate (CPPD) crystals respectively, in the  synovial fluid obtained from affected joints. Their identification is  usually based on skilled examination using polarizing light microscopy  (PLM) and the identification of negatively birefringent crystals (monosodium irate) or positively birefiringement crystals (CPPD, which must be intracellular for the diagnosis of pseudo gout) ; the determination  of blood uric acid concentration might also be carried out.

Non-steroidal anti-inflammatory drugs (NSAIDs) and corticosteroids are  commonly used in treatment of gout and pseduogout and for those who cannot tolerate NSAIDs, the  anti-inflammatory drug colchicine, originally extracted from meadow  saffron, is often used to treat gout. For those affected with gout, dietary changes are usually recommended  to help lower levels of uric acid and allopurinol (a xanthine  oxidase inhibitor) or probenecid (which prevents uric acid from being  reabsorbed from the kidneys) might be prescribed for long-term  preventative care.

At the doctor's bench

Rheumatologist Nora Singer of Case Western Reserve University School of  Medicine, in Cleveland, Ohio explains that the objective of the current  study was to demonstrate the usefulness of a shoebox sized point of  service clinical grade Raman spectrometer for reducing the time to clear  clinical diagnosis of gout and pseudogout (chondrocalcinosis, which most  commonly affects the knees). The hope is that such an instrument could  avoid the need for laboratory testing of synovial, or joint, fluid and  so preclude the need for complicated laboratory testing, the results  from which are not immediately available to doctor and patient.

The team's desktop instrument developed by the Akkus laboratory at Case Western Reserve University identifies MSU and CPPD crystals in  synovial fluid specifically and has been tested on eighty samples to  demonstrate efficacy. "The value in bench-top RS lies in the ability to  quickly and accurately detect the presence of MSU and CPPD crystals,"  says Singer. "Identification of MSU as evidence of gout flare  facilitates prompt treatment with outpatient follow-up." However, the RS  approach cannot yet determine whether or not CPPD crystals are  intracellular, which would give a diagnosis of pseudogout and require  different treatment and follow-up. Nevertheless, the team is confident  that RS could help guide initiation of targeted outpatient therapy and  potentially reduce the need for inpatient admission in patients with  joint effusion, in whom diagnosis might otherwise be uncertain.

"This  could potentially improve use of inpatient resources and the overall  quality of patient care and should now be tested in a clinical trial,"  adds Singer.

Related Links

Amer College Rheumatol 2014: "Annual Meeting"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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