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difference between dark field and bright field microscopy

Nailfold Capillaroscopy Excludes Scleroderma in Raynaud’s

Nailfold Capillaroscopy Excludes Scleroderma in Raynaud’s

he absence of a systemic sclerosis (SSc) nailfold pattern in patients with Raynaud’s phenomenon or suspected connective tissue disease is of high clinical value as a biomarker to rule out SSc, according to a large cohort study from the U.K.

For identifying patients who met the 2013 American College of Rheumatology/European League Against Rheumatism or the Very Early Diagnosis of Systemic Sclerosis (VEDOSS) criteria for SSc, the study found that a nailfold capillaroscopy pattern had a negative predictive value of 90% (95% CI 86 to 93), according to Maya H. Buch, MBChB, PhD, and colleagues from the University of Leeds, writing in BMC Musculoskeletal Disorders.

That pattern also had a sensitivity of 71% (95% CI 61 to 80), a specificity of 95% (95% CI 91 to 97), and a positive predictive value of 84% (95% CI 74 to 91).

“We were very impressed with nailfold capillaroscopy’s utility in negative prediction,” Buch said in an interview with MedPage Today. “The most valuable result here is the low likelihood of scleroderma in patients with Raynaud’s phenomenon who do not have any scleroderma-specific features on nailfold capillaroscopy. In practice, this means we can more confidently reassure such a patient and discharge care back to the patient’s general practitioner.”

The researchers noted that to the best of their knowledge, this is the first study to demonstrate that the absence of any SSc pattern on nailfold capillaroscopy maintains its known negative predictive value, including for patients with secondary Raynaud’s phenomenon, who are considered at increased risk of SSc. “This study is only one of two to include a large unselected cohort of patients with Raynaud’s phenomenon — mirroring clinical practice in which rheumatology departments frequently receive referrals of patients with Raynaud’s from GPs,” Buch said.

Primary Raynaud’s phenomenon is associated with normal microcirculation architecture, whereas microangiopathies are associated with secondary Raynaud’s, she explained. The SSc nailfold capillaroscopy pattern correlates with disease duration and severity, and also predicts future vascular and visceral organ damage. Nailfold capillaroscopy also detects vascular problems in glaucoma.

Although an SSc nailfold capillaroscopy pattern is sometimes present in other connective tissue diseases, “nailfold capillaroscopy could be performed to provide reassurance to the rheumatologist in the assessment of both [primary and secondary] Raynaud’s phenomenon,” the researchers wrote.

Buch and colleagues studied 347 patients referred for nailfold capillaroscopy to a tertiary-care center from January 2009 to October 2013. The mean age of the cohort was 47 years and 83% were female. Clinical review showed that 54 patients (16%) did not have true Raynaud’s phenomenon, 69 (20%) had primary Raynaud’s, 172 (50%) had secondary Raynaud’s, and 52 (15%) had SSc.

At referral, 46 patients (89%) met either VEDOSS or the 2013 American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) criteria for SSc. Of the patients with secondary Raynaud’s, 71 (41%) were being managed for connective tissue disease or inflammatory arthritis, while 101 (59%) had an antibody and/or a red-flag feature for SSc.

A nailfold capillaroscopy pattern for SSc was detected in 80 patients (23%) — 43 with early, 31 with active, and six with late-pattern vasculopathy. This pattern was observed in 37 patients (71%) diagnosed with SSc, 30 (17%) with secondary Raynaud’s, nine (13%) with primary Raynaud’s, and four (7%) without Raynaud’s.

Considering only those patients with non-SSc connective tissue disease or inflammatory arthritis, 16 of 71 patients (23%) had an SSc pattern. This was detected in two of five patients with SLE, eight of 42 with undifferentiated connective tissue disease, four of six with mixed connective tissue disease, one of three with Sjogren’s syndrome, and one of 14 with inflammatory arthritis.

Interestingly, the team said, participants meeting ACR/EULAR criteria were more likely to have an SSc nailfold capillaroscopy pattern than those meeting the VEDOSS criteria were: 84% versus 42%, respectively. “This may be related to the earlier stage of disease in those meeting VEDOSS with less time for detectable vasculopathic changes at the nailfold to develop,” the researchers wrote. “These findings are important as the earlier detection and management of SSc may lead to reduced morbidity and earlier detection of its complications.”

Among the study limitations were the lack of formal measurements to determine enlarged capillaries and the use of two different nailfold capillaroscopy methods, which might have introduced bias. As in clinical practice, the examiners were not blinded to the clinical diagnosis, possibly introducing investigator bias. In addition, the retrospective analysis may have missed important data, particularly the presence of telangiectasia.

The authors cited the need for larger, more defined prospective studies of a heterogeneous group of Raynaud’s patients. Buch noted that the current study is part of a larger Leeds program to identify biomarkers for accurately identifying patients at risk for scleroderma or those with scleroderma at risk for poorer outcomes.

difference between dark field and bright field microscopy

What is difference between dark field and bright field microscopy?

What is difference between dark field and bright field microscopy?

Darkfield microscopy is a specialized illumination technique that capitalizes on oblique illumination to enhance contrast in specimens that are not imaged well under normal brightfield illumination conditions. After the zeroth order (direct) light has been blocked by an opaque stop in the substage condenser, light passing through the specimen from oblique angles at all azimuths is diffracted, refracted, and reflected into the microscope objective to form a bright image of the specimen superimposed onto a dark background.

Transmitted Darkfield Illumination – Transmitted darkfield illumination can be used to increase the visibility of specimens lacking sufficient contrast for satisfactory observation and imaging by ordinary brightfield microscopy techniques. This section discusses various aspects of darkfield illumination, including theory of the technique, condenser design for transmitted darkfield illumination (at both low and high magnifications), microscope configuration parameters, and suggestions for choosing suitable candidates for observation.

Reflected Darkfield Illumination – Darkfield illumination with reflected light enables visualization of grain boundaries, surface defects, and other features that are difficult or impossible to detect with brightfield illumination. The technique relies on an opaque occluding disk, which is placed in the path of the light traveling through the vertical illuminator so that only the peripheral rays of light reach the deflecting mirror. These rays are reflected by the mirror and pass through a hollow collar surrounding the objective to illuminate the specimen at highly oblique angles.

Darkfield Illumination for Stereomicroscopy – Darkfield observation in stereomicroscopy requires a specialized stand containing a reflection mirror and light-shielding plate to direct an inverted hollow cone of illumination towards the specimen at oblique angles. A number of aftermarket products are currently available for retrofitting stereomicroscopes with transmitted darkfield illumination. In addition, many of the microscope manufacturers offer illumination accessories that can be conveniently utilized to achieve darkfield conditions for their stereo systems. The principal elements of darkfield illumination are the same for both stereomicroscopes and more conventional compound microscopes.

Darkfield Microscope Configuration – A step-by-step guide to configuration of transmitted light microscopes for use with both low and high magnification darkfield condensers is provided in this review. Careful attention should always be given to microscope alignment and configuration, irrespective of whether the illumination mode is brightfield, darkfield, phase contrast or some other contrast enhancement technique. Time spent in this endeavor will be repaid in excellent performance of the microscope both for routine observation and critical digital imaging or photomicrography.

Troubleshooting difference between dark field and bright field microscopy – There are numerous common problems associated with darkfield microscopy and photomicrography or digital imaging. These range from insufficient illumination and condenser mis-alignment to using a field stop of incorrect size. Most darkfield illumination problems are associated with the substage condenser, and this should be the first suspect when things do not work properly. This section addresses some of the more common problems encountered with darkfield microscopy, along with suggested remedies.

Darkfield Photomicrograph Gallery – The Molecular Expressions gallery of darkfield illumination photomicrography and digital imaging contains a wide spectrum of images captured under a variety of conditions and utilizing many different specimens. Included in this unique gallery are specimens ranging from simple diatoms to fossilized dinosaur bones, insects, Moon rocks, and integrated circuits.

difference between dark field and bright field microscopy Interactive Tutorials – Explore various aspects of darkfield microscopy theory and practice using these tutorials, which are designed to complement text pages by enabling visitors to use a web browser to simulate configuration and operation of a microscope under darkfield illumination. Both the theory and practice of darkfield microscopy are addressed by the tutorials.

difference between dark field and bright field microscopy

What is a difference between dark field and bright field microscopy?

What is a difference between dark field and bright field microscopy? The dark field microscopic examination of freshly collected, vital blood is a pillar of the Paracelsus Clinica al Ronc holistic medical diagnosis. It provides information on the internal milieu and function of the blood cells, as well as the amount and development of endobionts, from which microorganisms and more sophisticated structures, such as bacteria, fungi, and viruses, develop.

difference between dark field and bright field microscopy

What PRINCIPLE of difference between dark field and bright field microscopy?

What PRINCIPLE of difference between dark field and bright field microscopy?

The compound microscope may be fitted with a dark field condenser that has a numerical aperture (resolving power) greater than the objective. The condenser also contains a dark-field stop. The compound microscope now becomes a dark-field microscope. Light passing through the specimen is diffracted and enters the objective lens, whereas undiffracted light does not, resulting in a bright image against a dark background. Objects are seen as light objects against a dark background.

difference between dark field and bright field microscopy

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