A customized Raman system for point-of-care detection of arthropathic crystals in the synovial fluid

Abstract

Monosodium urate (MSU) and calcium pyrophosphate dihydrate (CPPD) are the most frequently observed crystals in joint space, leading to painful arthropathies. Correct diagnosis of the crystal identity is critical for the appropriate course of treatment. In this work, a custom Raman device in combination with a practical and efficient sample preparation method is used for chemically selective diagnosis of MSU and CPPD crystals in an automated fashion. The samples were prepared by a brief enzymatic digestion treatment of synovial fluid followed by a customized filtration process which was able to congregate crystals over a submillimeter sized spot. The data acquisition and collection was automated to collect multiple spectra distributed over the filtration spot. The performance of the cost-efficient Raman system was compared to a research-grade high fidelity Raman instrument. The custom-designed Raman device could detect MSU crystals at sub-clinical concentration of 0.1 μg/mL, and 1 μg/mL for CPPD crystals. This practical sample preparation approach in tandem with the low-cost customized Raman device has a potential to be a novel tool for point-and-shoot Raman diagnosis of arthritic crystals in synovial fluid at the point of care.

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

“…Dissolution of uric acid was confirmed by cross‐polarized imaging at high magnification. Previous research from our group demonstrated that this pretreatment process, including the digestion and the uric acid supplementary buffer, preserves the crystals, as confirmed by the lack of significant difference between crystal counts performed before versus after treatment. It was also affirmed that artifactual nucleation of crystals from the buffer does not occur.…”

“…First, a disposable syringe–microfiltration step was performed, which included a brief digestion and dilution to collect and concentrate crystals for Raman spectroscopic analysis. Second, a Raman spectroscopy step was performed, in which a shoebox‐sized optoelectromechanical system was customized for conducting an automated Raman spectroscopic analysis to identify crystal species, as detailed in a previous publication from our group .…”

“…Raman spectroscopy has been used in several studies to identify crystals in synovial fluid, but costly and bulky laboratory‐grade instruments were used, which limits the applicability of this technique in the clinic. Recent work from our laboratory addressed these challenges by developing an automated, shoebox‐sized point‐of‐care Raman spectroscopy (POCRS) device for use in the diagnosis of gout and pseudogout from synovial aspirates . The aim of the present study was to demonstrate the usefulness of the POCRS device in the diagnosis of gout and pseudogout, and to investigate the diagnostic agreement between POCRS and CPLM findings in a large clinical sample set.…”

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

“…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. 26 The detection limit of Raman spectroscopy is lower than that reported for CCA. 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).…”

“…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.…”