A Point‐of‐Care Raman Spectroscopy–Based Device for the Diagnosis of Gout and Pseudogout: Comparison With the Clinical Standard Microscopy

Abstract

Objective To demonstrate the usefulness of a novel medical device based on Raman spectroscopy for the rapid point-of-care diagnosis of gout and pseudogout. Methods A shoebox-sized point-of-care Raman spectroscopy (POCRS) device was developed for use in the diagnosis of gout and pseudogout. The device included a disposable syringe microfiltration kit to collect arthropathic crystals from synovial fluid and a customized automated Raman spectroscopy system to chemically identify crystal species. Diagnosis according to the findings of POCRS was compared with the clinical standard diagnosis based on compensated polarized light microscopy (CPLM) of synovial fluid aspirates collected from symptomatic patients (n = 174). Kappa coefficients were used to measure the agreement between POCRS and CPLM findings. Results Overall, POCRS and CPLM results were consistent in 89.7% of samples (156 of 174). For the diagnosis of gout, the kappa coefficient for POCRS and CPLM was 0.84 (95% confidence interval [95% CI] 0.75–0.94). For the diagnosis of pseudogout, the kappa coefficient for POCRS and CPLM was 0.61 (95% CI 0.42–0.81). Conclusion Kappa coefficients indicated that there was excellent agreement between POCRS and CPLM for the diagnosis of gout, with good agreement for the diagnosis of pseudogout. The POCRS device holds the potential to standardize and expedite the time to clinical diagnosis of gout and pseudogout, especially in settings where certified operators trained for CPLM analysis are not available.

Systematic review and quality analysis of emerging diagnostic measures for calcium pyrophosphate crystal deposition disease

“…Diagnostic approaches to crystal arthropathies include emerging 'point of care' methodologies, exemplified by adaptation of Raman spectroscopy. 28 As the field moves forward, we anticipate seeing similar adaptation of other, highly specific crystal analytic methods, such as FTIR spectroscopy. 29 However, cost-effectiveness relative to CPLM is not assured.…”

“…16 22 neck 20 and Achilles tendon/ plantar fascia. 9 The age of patients ranged from 18 28 to 98 22 years, and the proportion of males ranged from 22.9% 11 to 70.4%. 14 The mean disease duration was described in three studies 8 10 12 and ranged from 5.6 to 6 years.…”

“…Raman spectroscopy is a chemical analysis technique that is 100% specific in fingerprinting species based on the identification of chemical bonds unique to each material. 28 We reviewed four major studies [25][26][27][28] comparing Raman spectroscopy and CPLM. It was found that point of care Raman (POCR) spectroscopy can detect monosodium urate and CPPD crystals with good sensitivity and specificity at concentrations as low as 5 and 2.5 μg/ mL, 25 and 0.1 and 1 μg/mL.…”

“…Further study using a larger clinical sample set revealed that CPLM and POCR analyses agreed in 89.7% of samples (156 of 174), κ coefficients indicated that POCR and CPLM had excellent agreement in diagnosing gout (0.84 with 95% CI 0.75 to 0.94), and good, but less broad agreement in diagnosing acute CPP crystal arthritis (pseudogout; 0.61 with 95% CI 0.42 to 0.81). 28 The results suggested that POCR can be used in settings where there are Figure 2 Graphical display for QUADAS-2 results. We assessed methodological quality by the QUADAS-2 tool, to evaluate the risk of bias and applicability of primary diagnostic accuracy studies, as described in the text.…”

Editorial: Decreasing Crystal‐Induced Consternation: New Methods of Crystal Identification

“…In this issue of Arthritis & Rheumatology , Li et al describe a shoebox‐sized Raman spectroscope they constructed. This device identifies the chemical composition of particulates in synovial fluid and might be adaptable to widespread clinical use.…”