Purpose of review

The present review addresses diagnostic methods for crystalline arthritis including synovial fluid analysis, ultrasound, and dual energy CT scan (DECT).

Recent findings

There are new technologies on the horizon to improve the ease, sensitivity, and specificity of synovial fluid analysis. Raman spectroscopy uses the spectral signature that results from a material's unique energy absorption and scatter for crystal identification. Lens-free microscopy directly images synovial fluid aspirate on to a complementary metal-oxide semiconductor chip, providing a high-resolution, wide field of view (∼20 mm) image. Raman spectroscopy and lens-free microscopy may provide additional benefit over compensated polarized light microscopy synovial fluid analysis by quantifying crystal density in synovial fluid samples. Ultrasound and DECT have good sensitivity and specificity for the identification of monosodium urate (MSU) and calcium pyrophosphate (CPP) crystals. However, both have limitations in patients with recent onset gout and low urate burdens.

Summary

New technologies promise improved methods for detection of MSU and CPP crystals. At this time, limitations of these technologies do not replace the need for synovial fluid aspiration for confirmation of crystal detection. None of these technologies address the often concomitant indication to rule out infectious arthritis.

Hidradenitis suppurativa (HS) is a chronic, often debilitating skin condition that disproportionately impacts women in the United States and other Western nations. Dermatologists should consider incorporating palliative care principles into HS management to optimize care. Primary palliative care principles include utilizing evidence-based frameworks in serious illness communication, acknowledging and addressing physical and psychosocial suffering, recognizing and validating the burden of disease in partners, families, and caregivers, and engaging in collaborative care coordination. Certain patients may also benefit from outpatient, or sometimes inpatient, palliative care specialist collaboration, such as those with refractory HS and superimposed challenging psychosocial dynamics and symptom burden. Through integration of these palliative care domains into HS care, dermatologists can optimize their ability to provide comprehensive and compassionate care for patients suffering with this disease.

To describe the characteristics of calcium pyrophosphate (CPP) crystal size and morphology under compensated polarized light microscopy (CPLM). Secondarily, to describe CPP crystals seen only with digital enhancement of CPLM images, confirmed with advanced imaging techniques. Clinical lab-identified CPP-positive synovial fluid samples were collected from 16 joint aspirates. Four raters used a standardized protocol to describe crystal shape, birefringence strength and color. A crystal expert confirmed CPLM-visualized crystal identification. For crystal measurement, a high-pass linear light filter was used to enhance resolution and line discrimination of digital images. This process identified additional enhanced crystals not seen by raters under CPLM. Single-shot computational polarized light microscopy (SCPLM) provided further confirmation of the enhanced crystals' presence. Of 932 suspected crystals identified by CPLM, 569 met our inclusion criteria, and 293 (51%) were confirmed as CPP crystals. Of 175 unique confirmed crystals, 118 (67%) were rods (median area 3.6 μm2 [range, 1.0-22.9 μm2]), and 57 (33%) were rhomboids (median area 4.8 μm2 [range, 0.9-16.7 μm2]). Crystals visualized only after digital image enhancement were smaller and less birefringent than CPLM-identified crystals. CPP crystals that are smaller and weakly birefringent are more difficult to identify. There is likely a population of smaller, less birefringent CPP crystals that routinely goes undetected by CPLM. Describing the characteristics of poorly visible crystals may be of use for future development of novel crystal identification methods.