A Reagent and Virus Benchmarking Panel for a Uniform Analytical Performance Assessment of N Antigen-Based Diagnostic Tests for COVID-19.

Rapid diagnostic tests (RDTs) that detect antigen indicative of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection can help in making quick health care decisions and regularly monitoring groups at risk of infection. With many RDT products entering the market, it is important to rapidly evaluate their relative performance. Comparison of clinical evaluation study results is challenged by protocol design variations and study populations. Laboratory assays were developed to quantify nucleocapsid (N) and spike (S) SARS-CoV-2 antigens. Quantification of the two antigens in nasal eluates confirmed higher abundance of N than S antigen. The median concentration of N antigen was 10 times greater than S per genome equivalent. The N antigen assay was used in combination with quantitative reverse transcription (RT)-PCR to qualify a panel composed of recombinant antigens, inactivated virus, and clinical specimen pools. This benchmarking panel was applied to evaluate the analytical performance of the SD Biosensor Standard Q COVID-19 antigen (Ag) test, Abbott Panbio COVID-19 Ag rapid test, Abbott BinaxNOW COVID-19 Ag test, and the LumiraDx SARS-CoV-2 Ag test. The four tests displayed different sensitivities toward the different panel members, but all performed best with the clinical specimen pool. The concentration for a 90% probability of detection across the four tests ranged from 21 to 102 pg/mL of N antigen in the extracted sample. Benchmarking panels provide a quick way to verify the baseline performance of a diagnostic and enable direct comparisons between diagnostic tests. IMPORTANCE This study reports the results for severe acute respiratory syndrome coronavirus-2 (SARS-COV-2) nucleocapsid (N) and spike (S) antigen quantification assays and their performance against clinical reverse transcription (RT)-PCR results, thus describing an open-access quantification method for two important SARS-CoV-2 protein analytes. Characterized N antigen panels were used to evaluate the limits of detection of four different rapid tests for SARS-CoV-2 against multiple sources of nucleocapsid antigen, demonstrating proof-of-concept materials and methodology to evaluate SARS-CoV-2 rapid antigen detection tests. Quantification of N antigen was used to characterize the relationship between viral count and antigen concentration among clinical samples and panel members of both clinical sample and viral culture origin. This contributes to a deeper understanding of protein antigen and molecular analytes and presents analytical methods complementary to clinical evaluation for characterizing the performance of both laboratory-based and point-of-care rapid diagnostics for SARS-CoV-2.

Socioeconomic differentials of trends in the prevalence and economic burden of chronic obstructive pulmonary disease in rural southwest China.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a leading cause of mortality and morbidity, and imposes a substantial financial burden on society. However, few studies have examined the role of individual socioeconomic status (SES) in temporal trends of COPD prevalence and economic cost. This study aimed to uncover the changing prevalence and economic burden of COPD across socioeconomic gradients in rural southwest China. METHODS: Data were collected from two cross-sectional health interviews and examination surveys administered 10 years apart among individuals aged ≥ 35 years in rural China. A prevalence-based cost-of-illness method was used to estimate the cost of COPD. The individual socioeconomic position (SEP) index was constructed using principal component analysis. Post-bronchodilator spirometry tests were performed for each participant. RESULTS: From 2011 to 2021, the prevalence of COPD increased from 8.7% to 12.8% (P < 0.01), while the economic cost of COPD increased 1.9-fold. Unit hospital costs and outpatient costs increased 1.57-fold and 1.47-fold, while unit medication costs fell by 10.6%. Increasing prevalence was also observed when the data were stratified by sex, age, ethnicity, level of education, level of income, and SEP (P < 0.05). Men, ethnic minorities, and those with a lower educational level, lower income, or lower SEP had a higher prevalence of COPD than their counterparts both in 2011 and 2021 (P < 0.05). Unit outpatient costs and medication costs increased with patients' SEP in both survey years (P < 0.05). CONCLUSIONS: The prevalence and economic costs of COPD increased substantially across all socioeconomic gradients in rural southwest China in the decade from 2011 and 2021. Future COPD prevention and management interventions as well as efforts to improve access to affordable COPD medication and treatment should focus in particular on ethnic minority and low SEP populations.

Socioeconomic and lifestyle determinants of the prevalence of hypertension among elderly individuals in rural southwest China: a structural equation modelling approach.

BACKGROUND: This study examines the association between socioeconomic and lifestyle factors and the prevalence of hypertension among elderly individuals in rural Southwest China. METHODS: A cross-sectional survey of 4833 consenting adults aged ≥ 60 years in rural regions of Yunnan Province, China, was conducted in 2017. Data on individual socioeconomic status, sleep quality, physical activity level, and family history of hypertension were collected with a standardized questionnaire. Blood pressure, fasting blood glucose, height, weight, and waist circumference were also measured. An individual socioeconomic position (SEP) index was constructed using principal component analysis. Structural equation modelling (SEM) was applied to analyse the association between socioeconomic and lifestyle factors and the prevalence of hypertension. RESULTS: The overall prevalence of hypertension was 50.6% in the study population. Body fat distribution, including measures of obesity and central obesity, had the greatest total effect on hypertension (0.21), followed by family history of hypertension (0.14), biological sex (0.08), sleep quality (- 0.07), SEP (- 0.06), physical inactivity (0.06), and diabetes (0.06). Body fat distribution, SEP, and family history of hypertension had both direct and indirect effects on hypertension, whereas physical inactivity, diabetes, and sleep quality were directly associated with the prevalence of hypertension. Biological sex was indirectly associated with the prevalence of hypertension. CONCLUSIONS: SEP, body fat distribution, physical inactivity, diabetes, and sleep quality critically influence the prevalence of hypertension. Future interventions to prevent and control hypertension should give increased attention to individuals with low SEP and should focus on controlling diabetes and obesity, increasing physical activity levels, and improving quality of sleep among older adults aged ≥ 60 years in rural Southwest China.

Socioeconomic variations in chronic obstructive pulmonary disease prevalence, diagnosis, and treatment in rural Southwest China.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a major and growing cause of morbidity and mortality throughout the world. However, there remains a limited understanding of the association between individual socioeconomic status (SES) and COPD diagnosis and treatment worldwide, including in China. This study investigates socioeconomic variations in prevalence, diagnosis, and treatment of COPD in rural China. METHODS: The present study employed a cross-sectional survey design. The study population was composed of Han majority as well as Na Xi and Bai ethnic minority individuals 35 years of age and older living in Yunnan Province from 2017 to 2019. In total, 7534 individuals consented to participate in the study and complete a structured interview as well as a post-bronchodilator spirometry test. Multivariate logistic regression was used to analyze the association between individual socioeconomic status variables and the prevalence, diagnosis, and treatment of COPD. RESULTS: The age-standardized prevalence of COPD in the present study was 14.3%. Prevalence differed by gender: prevalence for men was 17.1%, versus 11.4% for women (P = 0.0001). Overall, levels of diagnosis and treatment of COPD for participants with COPD were 24.2 and 23.1%, respectively. Multivariate logistic regression indicated that higher educational levels and good access to medical services was associated with an overall lower risk of COPD (P = 0.032 vs. P = 0.018) as well as a higher probability of COPD diagnosis among those with COPD (P = 0.0001 vs. P = 0.002). Participants with COPD with higher educational levels (P = 0.0001) and higher annual household incomes (P = 0.0001) as well as good access to medical services (P = 0.016) were more likely to receive COPD medications and treatment than their counterparts. While Na Xi and Bai participants had a higher probability of having COPD (P = 0.0001), they had a lower probability of having received a diagnosis or treatment for COPD than Han participants (P = 0.0001 vs. P = 0.0012). CONCLUSIONS: Future interventions to further control COPD and improve diagnosis and treatment should focus on ethnic minority communities, and those with low education levels, low annual household incomes, and poor access to medical services.

Short-Term Trends in Economic Burden and Catastrophic Costs of Type 2 Diabetes Mellitus in Rural Southwest China.

OBJECTIVES: This study is aimed at gaining insights on the changing prevalence, economic burden, and catastrophic costs of diabetes in rural southwest China. MATERIALS AND METHODS: Data were collected from two cross-sectional health interviews and examination surveys among individuals aged ≥ 35 years in rural Yunnan Province. A prevalence-based cost-of-illness method was used to estimate the cost of diabetes. Information about the participants' demographic characteristics and economic consequences of diabetes was obtained using a standard questionnaire. Fasting blood sugar levels were recorded for each study participant. RESULTS: During the study period, the overall prevalence of diabetes increased from 7.7% to 9.5% (P < 0.01) and the economic cost of diabetes increased 1.52-fold. The largest increases were observed in hospital costs (1.77-fold increase), while unit medication costs fell by 18.6%. Both in 2009 and in 2016, males had higher overall direct and indirect costs of diabetes than females (P < 0.05). Direct costs represented the largest component of economic cost of diabetes while hospital costs were the main drivers of direct medical expenditures, accounting for 66.2% of the total direct costs in 2009 and 75.9% in 2016. The incidence of household catastrophic health payment and household impoverishment due to diabetes was 24.0% and 17.9% in 2009 and 23.6% and 17.6% in 2016, respectively. These rates did not differ between the two survey years (P > 0.05). CONCLUSIONS: The prevalence and economic burden of diabetes increased substantially from 2009 to 2016 in rural southwest China. The findings underscore an urgent need for the government to invest more financial resources in the prevention of diabetes and improvement of access to affordable medication in rural southwest China.

Socioeconomic disparities in prevalence and behaviors of smoking in rural Southwest China.

BACKGROUND: This study examines how prevalence and behaviors of smoking differ by socioeconomic status among rural southwest Chinese adults. METHODS: A cross-sectional survey was conducted including 7743 adults aged ≥35 years in rural regions of Yunnan Province, China from 2016 to 2018. Information on individual socioeconomic status (SES), ethnicity, and self-reported smoking behaviors was collected utilizing a standardized questionnaire. The individual socioeconomic position (SEP) index was constructed using principal component analysis. Multivariate logistic regression models were used to analyze the association between individual SES variables and the prevalence and behaviors of smoking. RESULTS: In the study population, the overall prevalence rate of current smokers was 33.5%. Males had a markedly higher prevalence of current smokers than females (62.6% vs. 4.8%, P < 0.01). Of these smokers, 74.5% began smoking during adolescence, 88.8% had never attempted to quit smoking, and 81.1% reported smoking in public places. Ethnic minority participants and those with low levels of education and/or low SEP were more likely to use tobacco as well as more likely to start smoking, and regularly smoke, during adolescence (P < 0.01). Participants with poor access to medical services had a higher prevalence of current smoking than their counterparts (P < 0.01). Among current smokers, Han ethnicity, good access to medical services, and high SEP were positively associated with the probability of having attempted to quit smoking at least once, while a high level of education and high SEP were negatively associated with the probability of smoking in public places. CONCLUSIONS: Disparities in prevalence and behaviors of smoking exist across a diversity of indicators of individual SES in rural southwest China. Future tobacco cessation interventions should focus on men, ethnic minorities, and those with low education levels, poor access to medical services, and low SEP.

Ethnic disparities in prevalence and clustering of cardiovascular disease risk factors in rural Southwest China.

BACKGROUND: This study examines how prevalence and clustering of cardiovascular disease (CVD) risk factors differ by ethnicity and socioeconomic status (SES) among rural southwest Chinese adults. METHODS: A cross-sectional survey of 7027 adults aged ≥35 years of Han and four ethnic minority group descent (Na Xi, Li Shu, Dai, and Jing Po) was used to derive prevalence of tobacco smoking and exposure to secondhand smoke (SHS) as well as alcohol consumption and physical activity data. Anthropometric measurements were also taken, including height, weight, and waist and hip circumference, as well as blood pressure (BP) and fasting blood glucose (FBG) measurements. RESULTS: Current smoking and drinking status were the top two CVD risk factors in the study population. Dai ethnic minority participants had the highest prevalence of hypertension, obesity, and central obesity, whereas Jing Po ethnic minority participants had the highest prevalence of current smoking status, SHS exposure, and current drinking status (P < 0.01). Han participants had the highest prevalence of diabetes and physical inactivity (P < 0.01). 11.1% of all participants did not have any of the studied CVD risk factors, while 68.6% of Han, 60.2% of Na Xi, 50.7% of Li Shu, 82.2% of Dai, and 73.0% of Jing Po participants had clustering of two or more CVD risk factors. Prevalence of CVD risk factor clusters increased with age (P < 0.01). Males and individuals with lower education levels and lower annual household income were more likely to have CVD risk factors than their counterparts (P < 0.01). CONCLUSION: Clustering of CVD risk factors is common in rural southwest China. Ethnicity and individual SES significantly impact prevalence of CVD risk factors and their clustering.

Formative research to inform development of a new diagnostic for soil-transmitted helminths: Going beyond the laboratory to ensure access to a needed product.

Soil-transmitted helminths (STHs) affect more than 1.5 billion people. The global strategy to control STH infections requires periodic mass drug administration (MDA) based on prevalence among populations at risk determined by diagnostic testing. Widely used copromicroscopy methods to detect infection, however, have low sensitivity as the prevalence and intensity of STH infections decline with repeated MDA. More sensitive diagnostic tools are needed to inform program decision-making. Using an integrated product development process, PATH conducted qualitative and quantitative formative research to inform the design and development of a more sensitive test for STH infections. The research, grounded in a conceptual framework for ensuring access to health products, involved stakeholder analysis, key opinion leader interviews, observational site visits of ongoing STH surveillance programs, and market research including market sizing, costing and willingness-to-pay analyses. Stakeholder analysis identified key groups and proposed strategic engagement of stakeholders during product development. Interviews highlighted features, motivations and concerns that are important for guiding design and implementation of new STH diagnostics. Process mapping outlined current STH surveillance workflows in Kenya and the Philippines. Market sizing in 2016 was estimated around half a million tests for lower STH burden countries, and 1-2 million tests for higher STH burden countries. The cost of commodities per patient for a molecular STH diagnostic may be around $10, 3-4 times higher than copromicroscopy methods, though savings may be possible in time and staffing requirements. The market is highly price sensitive as even at $5 per test, only 27% of respondents thought the test would be used by surveillance programs. A largely subsidized STH control strategy and a semi-functional Kato-Katz test may have created few incentives for manufacturers to innovate in STH diagnostics. Diverse partnerships, as well as balancing needs and expectations for new STH diagnostics are necessary to ensure access to needed products.

Feasibility of utilizing the SD BIOLINE Onchocerciasis IgG4 rapid test in onchocerciasis surveillance in Senegal.

As effective onchocerciasis control efforts in Africa transition to elimination efforts, different diagnostic tools are required to support country programs. Senegal, with its long standing, successful control program, is transitioning to using the SD BIOLINE Onchocerciasis IgG4 (Ov16) rapid test over traditional skin snip microscopy. The aim of this study is to demonstrate the feasibility of integrating the Ov16 rapid test into onchocerciasis surveillance activities in Senegal, based on the following attributes of acceptability, usability, and cost. A cross-sectional study was conducted in 13 villages in southeastern Senegal in May 2016. Individuals 5 years and older were invited to participate in a demographic questionnaire, an Ov16 rapid test, a skin snip biopsy, and an acceptability interview. Rapid test technicians were interviewed and a costing analysis was conducted. Of 1,173 participants, 1,169 (99.7%) agreed to the rapid test while 383 (32.7%) agreed to skin snip microscopy. The sero-positivity rate of the rapid test among those tested was 2.6% with zero positives 10 years and younger. None of the 383 skin snips were positive for Ov microfilaria. Community members appreciated that the rapid test was performed quickly, was not painful, and provided reliable results. The total costs for this surveillance activity was $22,272.83, with a cost per test conducted at $3.14 for rapid test, $7.58 for skin snip microscopy, and $13.43 for shared costs. If no participants had refused skin snip microscopy, the total cost per method with shared costs would have been around $16 per person tested. In this area with low onchocerciasis sero-positivity, there was high acceptability and perceived value of the rapid test by community members and technicians. This study provides evidence of the feasibility of implementing the Ov16 rapid test in Senegal and may be informative to other country programs transitioning to Ov16 serologic tools.

Multilevel Analysis of Socioeconomic Determinants on Diabetes Prevalence, Awareness, Treatment and Self-Management in Ethnic Minorities of Yunnan Province, China.

OBJECTIVES: The objective of this manuscript is to investigate socioeconomic differences in prevalence, awareness, treatment and self-management of diabetes among ethnic minority groups in Yunnan Province, China. METHODS: We conducted a cross-sectional survey in a sample of 5532 Na Xi, Li Su, Dai and Jing Po ethnic minorities. Multilevel modeling was used to estimate odds ratios (OR) and 95% confidence intervals (CI) for diabetes prevalence, as well as the other outcomes. RESULTS: Higher individual educational level was associated with a higher rate of awareness, treatment, adherence to medicines and monitoring of blood glucose (OR = 1.87, 4.89, 4.83, 6.45; 95% CI: 1.26-2.77, 1.87-12.7, 1.95-11.9, 2.23-18.6, respectively). Diabetic respondents with better household assets tended to receive more treatment (OR = 2.81, 95% CI: 1.11-7.12) and to monitor their blood glucose (OR = 3.29, 95% CI: 1.48-7.30). Diabetic patients with better access to medical services were more likely to treat (OR = 7.09, 95% CI: 2.46-20.4) and adhere to medication (OR = 4.14, 95% CI: 1.46-11.7). Income at the contextual level was significantly correlated with diabetes prevalence, treatment and blood glucose monitoring (OR = 1.84, 3.04, 4.34; 95% CI: 1.20-2.83, 1.20-7.73, 1.45-13.0, respectively). CONCLUSIONS: Future diabetes prevention and intervention programs should take both individual and township-level socioeconomic factors into account in the study regions.