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| LETTER TO EDITOR |
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| Ahead of print publication |
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Simple alteration of light microscope to detect synovial fluid crystals
Manesh Manoj1, Rasmi Ranjan Sahoo2, Anupam Wakhlu3
1 Department of Clinical Immunology and Rheumatology, AKG Memorial Cooperative Hospital; Department of Clinical Immunology & Rheumatology, Dr. Shenoy's Care, Kannur, Kerala, India
2 Department of Clinical Immunology and Rheumatology, IMS and SUM Hospital, Bhubaneswar, Odisha, India
3 Department of Clinical Immunology and Rheumatology, Apollomedics Superspeciality Hospitals, Lucknow, Uttar Pradesh, India
| Date of Submission | 09-Feb-2022 |
| Date of Acceptance | 14-Mar-2022 |
| Date of Web Publication | 26-Jul-2022 |
Correspondence Address:
Manesh Manoj,
Department of Rheumatology and Clinical Immunology, AKG Memorial Cooperative Hospital, Talap, Kannur - 670 002, Kerala
India
 Source of Support: None, Conflict of Interest: None DOI: 10.4103/injr.injr_28_22
Dear Editor,
A very common dilemma many of us face in the rheumatology clinic is when a patient presents with ankle joint arthritis, denies a typical history of podagra in the past, and has hyperuricemia. This requires careful evaluation to differentiate gout, spondyloarthritides and other causes. The lack of access to costly equipment required for synovial fluid crystal examination (a good polarizing microscope may cost upward of Rs. 5–10 lakhs), the lack of reliability of synovial crystal study reports from the major laboratory chains, and the drastic difference in the management and prognosis of the various differential diagnoses make an easy to use method to identify uric acid crystals in a synovial fluid sample in the clinic highly desirable. We would like to bring to your attention a simple and cheap method to convert a simple light microscope into a polarizing microscope sufficient enough to detect uric acid crystals in the clinic. We used the Olympus® CH20i light microscope (Olympus Medical Systems India Pvt. Ltd., Gurugram, Haryana) [Figure 1]a (it was an old, unused piece obtained from the hospital laboratory). A polarizing kit (consisting of a polarizer lens and an analyzer lens) available from Olympus, costing about Rs. 5500, was mounted on the microscope as shown in [Figure 1]b and [Figure 1]c. A synovial fluid sample from a patient with previously diagnosed gout with a recent flare due to drug noncompliance was examined under simple light microscope [Figure 1]d and the polarizing kit installed [Figure 1]e. At the time of presentation, the patient had already been re-initiated on febuxostat by a primary care physician. Although the characteristic color changes due to positive birefringence may not be Elicitable, the characteristic needle-shaped crystals (in the background of the clinical presentation) are easily distinguished when this polarizing kit is used. Manual rotation of the polarizer mounted on the light source to the darkest background makes it easier to distinguish the crystals. The polarizer converts the light from the light source into plane-polarized light, which then falls on the synovial fluid specimen. This generates two waves, the ordinary and the extraordinary waves, which are at right angles to each other and are at different phases with each other as well. These two waves are then combined into a single plane using constructive and destructive interference using an analyzer, thus producing the final image. Calcium pyrophosphate crystals may also be detected in a similar manner, but the inability to detect birefringence and the presence of artifacts with similarly shaped structures may make it difficult to confidently distinguish these crystals using this method. In centers with limited resources, this may prove to be a very useful technique to confirm gout and, possibly with further modifications, other crystal arthropathies. | Figure 1: (a) Olympus® CH20i microscope used for the demonstration; (b) The “analyzer” being placed inside the housing of the eyepiece; (c) the “polarizer” being placed on the light source – this can be rotated manually to adjust the background illumination; (d) the field of interest highlighted on simple light microscopy (black box, ×10); (e) the same field viewed using the polarizing kit installed, with the uric acid crystal shown enlarged (inset, ×10)
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Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
[Figure 1]
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