Calcium pyrophosphate crystal size and characteristics

A Novel Polarized Light Microscope for the Examination of Birefringent Crystals in Synovial Fluid

Background

The gold standard for crystal arthritis diagnosis relies on the identification of either monosodium urate (MSU) or calcium pyrophosphate (CPP) crystals in synovial fluid. With the goal of enhanced crystal detection, we adapted a standard compensated polarized light microscope (CPLM) with a polarized digital camera and multi-focal depth imaging capabilities to create digital images from synovial fluid mounted on microscope slides. Using this single-shot computational polarized light microscopy (SCPLM) method, we compared rates of crystal detection and raters' preference for image.

Methods

Microscope slides from patients with either CPP, MSU, or no crystals in synovial fluid were acquired using CPLM and SCPLM methodologies. Detection rate, sensitivity, and specificity were evaluated by presenting expert crystal raters with (randomly sorted) CPLM and SCPLM digital images, from FOV above clinical samples. For each FOV and each method, each rater was asked to identify crystal suspects and their level of certainty for each crystal suspect and crystal type (MSU vs. CPP).

Results

For the 283 crystal suspects evaluated, SCPLM resulted in higher crystal detection rates than did CPLM, for both CPP (51%. vs. 28%) and MSU (78% vs. 46%) crystals. Similarly, sensitivity was greater for SCPLM for CPP (0.63 vs. 0.35) and MSU (0.88 vs. 0.52) without giving up much specificity resulting in higher AUC.

Conclusions

Subjective and objective measures of greater detection and higher certainty were observed for SCPLM over CPLM, particularly for CPP crystals. The digital data associated with these images can ultimately be incorporated into an automated crystal detection system that provides a quantitative report on crystal count, size, and morphology.

Crystal arthropathies and osteoarthritis-where is the link?

Osteoarthritis (OA) is one of the leading causes of disability worldwide. As our understanding of OA progressively has moved from a purely mechanical "wear and tear" concept toward a complex multi-tissue condition in which inflammation plays a central role, the possible role of crystal-induced inflammation in OA incidence and progression may be relevant. In addition to gout, which affects 4% of the US population, basic calcium phosphate and calcium pyrophosphate deposition both may induce joint inflammation and may play a role in pain in OA. This narrative review article discusses the possible mechanisms underlying the associations between crystal-induced arthropathies and OA, and the important implications of these for clinical practice and future research.

Cholesterol Crystals as the Main Trigger of Interleukin-6 Production through Innate Inflammatory Response in Human Spontaneously Ruptured Aortic Plaques

AIM

This study aimed to clarify whether cholesterol crystals (CCs) are the main trigger of innate inflammation in human spontaneously ruptured aortic plaques (SRAPs).

METHODS

This study included 260 SRAPs collected during nonobstructive general angioscopy (NOGA) from 126 patients with confirmed or suspected coronary artery disease. Interleukin (IL)-6 levels in SRAPs were measured. IL-6 levels in the Valsalva sinus and femoral or brachial arteries were measured. IL-6 ratios (the IL-6 level in SRAPs and arteries divided by the IL-6 level at the Valsalva sinus at the beginning of the aorta) were calculated. Quantitative analysis of CCs was performed from SRAPs. The correlation between the count of CCs and IL-6 levels in SRAPs and that between the counts of CCs and IL-6 ratios in SRAPs were analyzed.

RESULTS

The IL-6 levels in SRAPs were 3.4 [2.1, 7.2] pg/mL, and the IL-6 ratio (median [interquartile range]) in SRAPs was 1.10 [1.00, 1.26]. CCs were detected in 94 of 260 SRAPs (36%). The count of CCs was 11,590 (95% confidence interval, 2,386-30,113) per 10 mL in CC-positive samples. There was a moderate correlation between the counts of CCs and IL-6 ratios in SRAPs (r=0.49, r＜0.0001), whereas there was no correlation between the count of CCs and IL-6 levels in SRAPs. The IL-6 ratios of the brachial and femoral arteries were 1.06 (95% CI, 0.99-1.20) and 1.11 (95% CI, 1.04-1.20), respectively.

CONCLUSIONS

CC is the main trigger of IL-6 production through innate inflammatory response in human SRAPs in situ.

Pseudogout of the lumbar spine

Calcium pyrophosphate deposition involves deposition of calcium pyrophosphate dihydrate crystals in various joints throughout the body. The term "pseudogout" refers to an acute attack of calcium pyrophosphate crystal-induced arthritis. Though clinical presentation and joint involvement vary, involvement of the lumbar spine is rare. We present the case of a 61-year-old male who presented with 3 days of worsening lower back pain. He had elevated inflammatory markers, leukocytosis, and spinal tenderness on exam. Magnetic resonance imaging of the lumbar spine showed likely L4-L5 osteomyelitis; however, biopsy of the disk space revealed extensive calcium pyrophosphate crystal deposition. The patient was treated with prednisone taper with alleviation of symptoms. Though pseudogout of the spine is rare, our report supports literature urging clinicians to consider pseudogout when assessing elderly patients with back pain for prompt and appropriate treatment.