Tag Archives: epidemiology

COVID-19 false-positive rate for “asymptomatic infected individuals” during screening estimated at up to 80%???

G H Zhuang, M W Shen, L X Zeng, B B Mi, F Y Chen, W J Liu, L L Pei, X Qi, C Li. [Potential False-Positive Rate Among the ‘Asymptomatic Infected Individuals’ in Close Contacts of COVID-19 Patients] Zhonghua Liu Xing Bing Xue Za Zhi, 41 (4), 485-488

Objective: As the prevention and control of COVID-19 continues to advance, the active nucleic acid test screening in the close contacts of the patients has been carrying out in many parts of China. However, the false-positive rate of positive results in the screening has not been reported up to now. But to clearify the false-positive rate during screening is important in COVID-19 control and prevention.

Methods: Point values and reasonable ranges of the indicators which impact the false-positive rate of positive results were estimated based on the information available to us at present. The false-positive rate of positive results in the active screening was deduced, and univariate and multivariate-probabilistic sensitivity analyses were performed to understand the robustness of the findings.

Results: When the infection rate of the close contacts and the sensitivity and specificity of reported results were taken as the point estimates, the positive predictive value of the active screening was only 19.67%, in contrast, the false-positive rate of positive results was 80.33%. The multivariate-probabilistic sensitivity analysis results supported the base-case findings, with a 75% probability for the false-positive rate of positive results over 47%.

Conclusions: In the close contacts of COVID-19 patients, nearly half or even more of the ‘asymptomatic infected individuals’ reported in the active nucleic acid test screening might be false positives.

An example of why best available science is needed when setting air quality regulations

The overall relative risks reported in this study are so low they do not even support the conclusions stated by the authors. Based on these relative risk findings following accepted practice there is no difference in risk and no meaningful opportunity for risk reduction by setting strict air quality limits, contrary to what the authors claim. If I am reading the article correctly, the reported associations are much weaker than weak (essentially, none).

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Ana M Vicedo-Cabrera, et al. Short term association between ozone and mortality: global two stage time series study in 406 locations in 20 countries, BMJ, 2020; 368, https://doi.org/10.1136/bmj.m108

Objective: To assess short term mortality risks and excess mortality associated with exposure to ozone in several cities worldwide.

Design: Two stage time series analysis.

Setting: 406 cities in 20 countries, with overlapping periods between 1985 and 2015, collected from the database of Multi-City Multi-Country Collaborative Research Network.

Population: Deaths for all causes or for external causes only registered in each city within the study period.

Main outcome measures: Daily total mortality (all or non-external causes only).

Results: A total of 45 165 171 deaths were analysed in the 406 cities. On average, a 10 µg/m3 increase in ozone during the current and previous day was associated with an overall relative risk of mortality of 1.0018 (95% confidence interval 1.0012 to 1.0024). Some heterogeneity was found across countries, with estimates ranging from greater than 1.0020 in the United Kingdom, South Africa, Estonia, and Canada to less than 1.0008 in Mexico and Spain. Short term excess mortality in association with exposure to ozone higher than maximum background levels (70 µg/m3) was 0.26% (95% confidence interval 0.24% to 0.28%), corresponding to 8203 annual excess deaths (95% confidence interval 3525 to 12 840) across the 406 cities studied. The excess remained at 0.20% (0.18% to 0.22%) when restricting to days above the WHO guideline (100 µg/m3), corresponding to 6262 annual excess deaths (1413 to 11 065). Above more lenient thresholds for air quality standards in Europe, America, and China, excess mortality was 0.14%, 0.09%, and 0.05%, respectively.

Conclusions: Results suggest that ozone related mortality could be potentially reduced under stricter air quality standards. These findings have relevance for the implementation of efficient clean air interventions and mitigation strategies designed within national and international climate policies.

CDC Guidance issued for 2019-nCoV

Excerpt from the CDC 2019-nCoV Situation Summary (here):

CDC Recommends

While the immediate risk of this new virus to the American public is believed to be low at this time, everyone can do their part to help us respond to this emerging public health threat:

Small epidemiological associations do not imply a significant risk

“When effects are this small, it is extremely possible that the effects are not real, but are artifacts of the statistical methods used in the original analysis.  If these findings had had Relative Risks or Risk Ratios of 4.0 or 7.9 or any value that might indicate a strong association, then I would be more convinced.  But with so many of the metrics not even passing the most basic test of significance, I am concerned that the findings represent only what John P.A. Ioannidis has termed “simply accurate measures of the prevailing bias.” “  click here

Meta-analyses are very squishy when something is made up out of nothing

S. Stanley Young and Warren B. Kindzierski. Evaluation of a meta-analysis of air quality and heart attacks, a case studyCritical Reviews in Toxicology  https://doi.org/10.1080/10408444.2019.1576587

It is generally acknowledged that claims from observational studies often fail to replicate. An exploratory study was undertaken to assess the reliability of base studies used in meta-analysis of short-term air quality-myocardial infarction risk and to judge the reliability of statistical evidence from meta-analysis that uses data from observational studies. A highly cited meta-analysis paper examining whether short-term air quality exposure triggers myocardial infarction was evaluated as a case study. The paper considered six air quality components – carbon monoxide, nitrogen dioxide, sulphur dioxide, particulate matter 10 lm and 2.5 lm in diameter (PM10 and PM2.5), and ozone. The number of possible questions and statistical models at issue in each of 34 base papers used were estimated and p-value plots for each of the air components were constructed to evaluate the effect heterogeneity of p-values used from the base papers. Analysis search spaces (number of statistical tests possible) in the base papers were large, median 1⁄4 12,288 (interquartile range 1⁄4 2496 ” 58,368), in comparison to actual statistical test results presented. Statistical test results taken from the base papers may not provide unbiased measures of effect for meta-analysis. Shapes of p-value plots for the six air components were consistent with the possibility of analysis manipulation to obtain small p-values in several base papers. Results suggest the appearance of heterogeneous, researcher-generated p-values used in the meta-analysis rather than unbiased evidence of real effects for air quality. We conclude that this meta-analysis does not provide reliable evidence for an association of air quality components with myocardial risk.

Dose-response meta-analysis of lung cancer risk and inorganic arsenic

Yuan T, Zhang H, Chen B, Zhang H, Tao S. Association between lung cancer risk and inorganic arsenic concentration in drinking water: a dose-response meta-analysis. Toxicol Res (Camb). 2018 Sep 18;7(6):1257-1266. doi: 10.1039/c8tx00177d.

High dose arsenic in drinking water (≥100 μg L-1) is known to induce lung cancer, but lung cancer risks at low to moderate arsenic levels and its dose-response relationship remains inconclusive. We conducted a systematic review of cohort and case-control studies that quantitatively reported the association between arsenic concentrations in drinking water and lung cancer risks by searching the PubMed database till June 14, 2018. Pooled relative risks (RRs) of lung cancer associated with full range (10 μg L-1-1000 μg L-1) and low to moderate range (<100 μg L-1) of water arsenic concentrations were calculated using random-effects models. A dose-response meta-analysis was performed to estimate the pooled associations between restricted cubic splines of log-transformed water arsenic and the lung cancer risks. Fifteen studies (9 case-control and 6 cohort studies) involving a total of 218 481 participants met the inclusion criteria. Meta-analysis identified significantly increased risks of lung cancer on exposure to both full range (RR = 1.21; 95% confidence interval [CI] = 1.05-1.37; heterogeneity I 2 = 54.3%) and low to moderate range (RR = 1.18; 95%CI = 1.00-1.35; I 2 = 56.3%) of arsenic-containing water. In the dose-response meta-analysis of eight case-control studies, we found no evidence of non-linearity, although statistical power was limited. The corresponding pooled RRs and their 95%CIs for exposure to 10 μg L-1, 50 μg L-1, and 100 μg L-1 water arsenic were 1.02 (1.00-1.03), 1.10 (1.04-1.15), and 1.20 (1.08-1.32), respectively. We provide evidence on the association between increased lung cancer risks and inorganic arsenic in drinking water across low, moderate and high levels. Minimizing arsenic levels in drinking water may be of public health importance.

Opportunities to reduce global cholera

Legros D; Partners of the Global Task Force on Cholera Control. Global Cholera Epidemiology: Opportunities to Reduce the Burden of Cholera by 2030. The Journal of infectious diseases. 2018 Sep 1. doi: 10.1093/infdis/jiy486.

While safe drinking water and advanced sanitation systems have made the Global North cholera-free for decades, the disease still affects 47 countries across the globe resulting in an estimated 2.86 million cases and 95,000 deaths per year worldwide. Cholera impacts communities already burdened by conflict, lack of infrastructure, poor health systems, and malnutrition. In October 2017, the Global Task Force on Cholera Control (GTFCC) launched an initiative titled Ending Cholera: A Global Roadmap to 2030, with the objective to reduce cholera deaths by 90% worldwide, and eliminate cholera in at least 20 countries by 2030. The GTFCC is working to position cholera control not as a vertical programme but instead using cholera as a marker of inequity and an indicator of poverty, linking the objectives of the Roadmap to the SDGs. The roadmap consists of targeted multi-sectoral interventions, supported by a coordination mechanism, along 3 axes: (1) early detection and quick response to contain outbreaks; (2) a multisectoral approach to prevent cholera recurrence in hotspots; (3) an effective partnership mechanism of coordination for technical support, countries capacity building, research and M&E, advocacy and resource mobilization. Every case and every death from cholera is preventable with the tools we have today.