The 2020 International Alliance for the Control of Scabies Consensus Criteria for the Diagnosis of Scabies

BACKGROUND

Scabies is a common parasitic skin condition that causes considerable morbidity globally. Clinical and epidemiological research for scabies has been limited by a lack of standardization of diagnostic methods.

OBJECTIVES

To develop consensus criteria for the diagnosis of common scabies that could be implemented in a variety of settings.

METHODS

Consensus diagnostic criteria were developed through a Delphi study with international experts. Detailed recommendations were collected from the expert panel to define the criteria features and guide their implementation. These comments were then combined with a comprehensive review of the available literature and the opinion of an expanded group of international experts to develop detailed, evidence-based definitions and diagnostic methods.

RESULTS

The 2020 International Alliance for the Control of Scabies (IACS) Consensus Criteria for the Diagnosis of Scabies include three levels of diagnostic certainty and eight subcategories. Confirmed scabies (level A) requires direct visualization of the mite or its products. Clinical scabies (level B) and suspected scabies (level C) rely on clinical assessment of signs and symptoms. Evidence-based, consensus methods for microscopy, visualization and clinical symptoms and signs were developed, along with a media library.

CONCLUSIONS

The 2020 IACS Criteria represent a pragmatic yet robust set of diagnostic features and methods. The criteria may be implemented in a range of research, public health and clinical settings by selecting the appropriate diagnostic levels and subcategories. These criteria may provide greater consistency and standardization for scabies diagnosis. Validation studies, development of training materials and development of survey methods are now required. What is already known about this topic? The diagnosis of scabies is limited by the lack of accurate, objective tests. Microscopy of skin scrapings can confirm the diagnosis, but it is insensitive, invasive and often impractical. Diagnosis usually relies on clinical assessment, although visualization using dermoscopy is becoming increasingly common. These diagnostic methods have not been standardized, hampering the interpretation of findings from clinical research and epidemiological surveys, and the development of scabies control strategies. What does this study add? International consensus diagnostic criteria for common scabies were developed through a Delphi study with global experts. The 2020 International Alliance for the Control of Scabies (IACS) Criteria categorize diagnosis at three levels of diagnostic certainty (confirmed, clinical and suspected scabies) and eight subcategories, and can be adapted to a range of research and public health settings. Detailed definitions and figures are included to aid training and implementation. The 2020 IACS Criteria may facilitate the standardization of scabies diagnosis.

Estimating the global burden of scabies: what else do we need?

Scabies is one of the most common disorders identified in any estimate of global skin disease prevalence. Furthermore, quantifying its impact on individuals and societies has been problematic. There has been a lack of clear case definitions and laboratory tests. There have been few epidemiological studies, particularly those focusing on low-income countries, variation in prevalence within high-income countries, or estimates of the effect of scabies on health beyond the skin, such as renal disease or mental wellbeing. Economic studies are also lacking. However, the new strategy of integrating surveillance for skin Neglected Tropical Diseases may well produce advancements on these issues, in addition to providing an overarching structure for health improvement and disease control.

P3131Evolution of subclinical rheumatic heart disease: a multi-centre retrospective cohort study

Background

Screening echocardiography (echo) detects subclinical rheumatic heart disease (RHD) which is categorised as definite or borderline. The natural history of subclinical RHD is not known. Follow up single centre studies have included a relatively small number of participants, and have shown variable progression rates.

Aim

To determine incidence of and factors associated with progression and regression among a cohort of children with baseline subclinical RHD across multiple countries and regions.

Methods

This is a retrospective cohort study of RHD evolution in children with subclinical RHD. Study sites were Australia, Fiji, Malawi, New Zealand, and Uganda. Progression or regression was determined from echos obtained at baseline and most recent follow-up. Factors associated with echo progression or regression were identified using multivariable logistic regression.

Results

482 participants (131 with definite, 351 with borderline subclinical RHD) from 5 countries were included (mean age 11.5 years, range 5–19 years). Mean follow up was 3.4 yrs (range 0.4–9.5 yrs). Of 482 participating children, 204 (42%) regressed. Among 131 children with definite lesions, 48 (37%) regressed to borderline or normal, and 83 (63%) remained definite. Among 351 children with borderline lesions, 39 (11.1%) progressed, 156 (44.4%) remained borderline, and 156 (44.4%) regressed to normal. World Heart Federation defines subcategories based on characteristics of affected valves. By subcategory, children with definite C (pathological aortic regurgitation and 2 morphologic characteristics of the aortic valve) and borderline A (at least 2 morphologic features of the mitral valve without pathologic mitral regurgitation or stenosis) were less likely to regress, and borderline A was more likely to progress. In univariable analysis, good adherence (>80%) to penicillin prophylaxis (BPG) was associated with more regression among all patients (definite + borderline) (OR 1.9, CI 1, 3.5; p=0.04) but this association did not remain significant after adjustment. With multivariable analysis, borderlines prescribed BPG was the only factor related to progression from borderline to definite (OR 4.1, CI 1.8, 9.3, p<0.01).

Conclusion

This is the largest reported subclinical RHD cohort followed to report outcomes. 42% of definite RHD regressed with subtype C more likely to regress. 11% of borderline RHD progressed. Borderline A was more likely to progress and less likely to regress. We have also identified that being prescribed BPG is associated with borderline progression. This is likely because children with more advanced borderline disease may be more likely to be prescribed BPG. This study highlights that RHD evolution is variable out to 3–4 years post echo detection. While borderline disease is likely, in some cases, to reflect the earliest change of RHD, how this should be monitored and whether it should be treated with BPG should be a priority for future prospective evaluation.

P3133Single parasternal long axis echocardiography by briefly trained health workers using handheld devices for detection of rheumatic heart disease: a prospective study of diagnostic accuracy

Introduction

Echocardiographic screening can detect rheumatic heart disease (RHD) in high-risk populations,but is limited by reliance on highly-trained experts and equipment. We sought to determine the diagnostic utility of an ultra-abbreviated single parasternal-long-axis-sweep of the heart (SPLASH) echocardiography protocol to detect RHD, performed by briefly-trained health workers.

Methods

In Timor-Leste and Northern Australia, individuals aged 5–20y were offered school-based echocardiographic screening. Health workers completed online modules followed by one-week of practical training, logging 50 echocardiograms prior to study. The index test was SPLASH, performed and reported by health workers using handheld GE V-scan devices. The index test was abnormal if any mitral or aortic regurgitation was detected. The reference test was a comprehensive echocardiogram, performed by an echocardiographers or cardiologist on a GE Vivid-Q, reported according to World Heart Federation criteria. The diagnostic accuracy of the index test was determined.

Results

2590 subjects underwent index and reference tests. Prevalence of definite RHD was 3.2% (83/2590). Sensitivity and specificity of index test were 0.75 (95% CI 0.64–0.83) and 0.77 (95% CI 0.75–0.78) respectively for detection of any definite RHD, and 0.91 (95% CI 0.74–0.98) and 0.76 (95% CI 0.74–0.78) respectively for detection of moderate or severe RHD.

Conclusion

Health workers using SPLASH detected the vast majority of moderate and severe RHD cases, but lacked sensitivity for detection of mild RHD. Further analysis is underway to evaluate the learning curve and other performance indicators of health workers performing and interpreting echocardiograms. This will allow refinement of SPLASH protocol and augmentation of health worker training to increase detection rates and accuracy for future population screening initiatives.

Acknowledgement/Funding

Heart Foundation Australia Vanguard Grant, Menzies HOT-NORTH pilot project grant, Snow Foundation, Rotary, Bawinanga Aboriginal Corporation, Mala'la

Scabies in the developing world--its prevalence, complications, and management

Scabies remains one of the commonest of skin diseases seen in developing countries. Although its distribution is subject to a cycle of infection, with peaks and troughs of disease prevalence, this periodicity is often less obvious in poor communities. Scabies is a condition that affects families, particularly the most vulnerable; it also has the greatest impact on young children. Largely through the association with secondary bacterial infection caused by group A streptococci and Staphylococcus aureus, the burden of disease is compounded by nephritis, rheumatic fever and sepsis in developing countries. However, with a few notable exceptions, it remains largely neglected as an important public health problem. The purpose of this review is to provide an update on the current position of scabies with regard to its complications and control in resource-poor countries.

Image analysis of soft-tissue in-growth and attachment into highly porous alumina ceramic foam metals

The detailed quantitative characterization of soft-tissue in-growth into highly porous artificial implants is critical to understanding the biophysical processes that will lead to the best structural scaffolding construct. Previous studies have performed mechanical peel tests and mostly qualitative histological analyses of soft-tissue. The goal of this paper is to report the results obtained from applying two image analysis algorithms to quantify the morphological structure found in histological images of stained soft-tissue in-growth into alumina ceramic foam metal implants using a canine model. Three different pore sizes were used and three different post-operative time points were considered. Using the 2D Wavelet Transform Modulus Maxima method and 2D Fourier Transform analysis, a strong anisotropic signature (directional preference) is detected in early (4-week) histological samples. The direction of preference is towards the center of the implants. The strength of the anisotropy at later time points (8 and 16 weeks) becomes gradually weaker. Our interpretation is that after a short period of time, the main tissue growth activity has been concentrated on filling the artificial implant by growing towards its center. The weaker anisotropic signature found at later time points is interpreted as the tissue growth activity strengthening its structure by growing in more random directions.

Myocardial adaptation to ischemia by oxidative stress induced by endotoxin

In this study, we examined the effects of oxidative stress adaptation on myocardial ischemic reperfusion injury. Oxidative stress was induced by injecting endotoxin (0.5 mg/kg) into the rat. After 24 h, rats were killed, hearts were isolated, and the effects of ischemia-reperfusion were studied using an isolated working heart preparation. The development of oxidative stress was examined by assessing malonaldehyde production in the heart. The antioxidant defense system was studied by estimating antioxidant enzyme activities and ascorbate- as well as thiol-dependent antioxidant reserve. The results of our study indicated that endotoxin induced oxidative stress within 1 h of treatment; the stress was reduced progressively and steadily up to 24 h. The antioxidant enzymes superoxide dismutase, catalase, glutathione (GSH) peroxidase, and GSH reductase were lowered up to 2 h and then increased. Both thiol- and ascorbate-dependent antioxidant reserve were enhanced, but the enhancement of the former was only transitory. After 24 h, endotoxin provided adequate protection to the heart from the ischemic-reperfusion injury, as evidenced by improved left ventricular function and aortic flow. Our results suggest that the induction of oxidative stress by endotoxin-induced adaptive modification of the antioxidant defense in the heart, thereby reducing ischemic-reperfusion injury.

Assignment of segments of the bacteriorhodopsin sequence to positions in the structural map

Specific amino acid sequence segments have been assigned to locations in the structural map of bacteriorhodopsin using two-dimensional neutron diffraction data and a model building analysis. Models are constructed computationally by building specific regions of the amino acid sequence as alpha helices and then positioning the helices on axes indicated by the density map of Henderson and Unwin (Nature [Lond.]. 1975, 257:28-32). Neutron diffraction data were collected from samples of stacked, oriented "native" purple membranes as well as purple membranes containing different kinds of deuterated amino acids. Models differing in the assignments of helices to specific axes and in rotations of the helices about those axes were tested against the neutron data using a weighted residual factor to rank the models. This residual factor was calculated between observed and predicted intensity differences for pairs of data sets. Using this approach, a small set of related models has been found that predicts the observed intensity changes between five independent data sets. These models are inconsistent with the proposed locations of the retinal chromophore and the carboxyl terminus and with any of the previously proposed models for bacteriorhodopsin.

The lac repressor protein: molecular shape, subunit structure, and proposed model for operator interaction based on structural studies of microcrystals

Electron microscopic and powder x-ray diffraction studies of small crystals of the lac repressor protein provide evidence on its molecular shape and subunit structure which in turn suggests a possible mode of repressor-operator interaction. The crystals are probably orthorhombic space group P222(1) with unit cell dimensions of a = 140, b = 91, c = 117 A. This tetrameric protein appears rather asymmetric, having approximate molecular dimensions of 140 A by 60 A by 45 A. The dumbbell shape of the projected molecular outline observed in the electron micrographs can be explained by assuming that the subunits are related by 222 symmetry and are placed at the corners of a plane rectangle. We propose a model for repressor-operator interaction in which the DNA binds to the repressor with its long axis aligned with that of the repressor and with its 2-fold axis coincident with a twofold axis of the repressor.