Prevalence assessment adjusted for laboratory test performance using an example of the COVID-19 serological tests

Assessment of the prevalence of the disease or condition should consider the accuracy of the diagnostic tests. In the context of the new coronavirus infection (COVID-19) pandemic, laboratory testing has been one of the most important components of the overall strategy for the control and prevention of this infection. Seroprevalence studies have been used to assess and monitor the level of population immunity to the virus. In this paper we provide detailed description of the methods to calculate and interpret the accuracy of laboratory tests as well as their sensitivity, specificity, positive- and negative prognostic values of laboratory tests using seroprevalence of COVID-19 studies as an example for better understanding of the methodological issues. The use of the laboratory tests accuracy in prevalence studies has been demonstrated. A sample syntax to calculate confidence intervals for the prevalence estimates using the bootstrap procedure with known absolute values of true positive and true negative results, false positive and false negative results for R software is also provided. Presentation of the prevalence estimates adjusted for test performance indicators with confidence intervals improves comparability of the findings obtained using different serological tests. The article is intended for undergraduate-, postgraduate-, and doctoral students in health sciences working with the assessment of the prevalence (seroprevalence) of diseases or conditions through population-based serological surveys

An Improved Limit on Invisible Decays of Positronium

The results of a new search for positronium decays into invisible final states are reported. Convincing detection of this decay mode would be a strong evid ence for new physics beyond the Standard Model (SM): for example the existence of extra--dimensions, of milli-charged particles, of new light gauge bosons or of mirror particles. Mirror matter could be a relevant dark matter candidate. In this paper the setup and the results of a new experiment are presented. In a collected sample of about $(6.31\pm0.28) \times 10^6$ orthopositronium decay s, no evidence for invisible decays in an energy window [0,80] keV was found and an upper limit on the branching ratio of orthopositronium \invdecay could be set: \binvdecay<4.2\times 10^{-7} (90% C.L.) Our results provide a limit on the photon mirror-photon mixing strength $\epsilon \leq 1.55\times 10^{-7}$ (90% C.L.) and rule out particles lighter than the electron mass with a fraction $Q_x \leq 3.4 \times 10^{-5}$ of the electron charge. Furthermore, upper limits on the branching ratios for the decay of parapositronium $Br(p-Ps\to invisible)\leq 4.3 \times 10^{-7}$ (90% C.L.) and the direct annihilation $Br(e^+e^-\to invisible)\leq 2.1 \times 10^{-8}$ (90% C.L.) could be set.Comment: 17 pages, 7 figures, added references, fixed limit on millicharged particles and changed two plots accordingl

Prevalence of metabolic phenotypes among citizens of Arctic area of the Russian Federation (in Arkhangelsk city setting)

BACKGROUND: Influence of obesity on the body at whole and with regard to metabolic changes is still unclear. In Russia there are a few data about prevalence of metabolic phenotypes among population based on epidemiological data.AIM: to assess the prevalence of metabolic phenotypes among citizens of Arctic area of the Russian Federation (in the Arkhangelsk city setting).MATERIALS AND METHODS: a cross-sectional study was conducted using a random sample of Arkhangelsk citizens (n=2380) 35–69 years old, which was obtained within a population study of cardiovascular diseases («Know your heart» (KYH)). The participants were divided into metabolic phenotypes according to the presence of obesity (BMI≥30 kg/m2) and metabolic syndrome (AHA/NHBLI): phenotype 1 — metabolically healthy normal weight, phenotype 2 — metabolically unhealthy normal weight, phenotype 3 — metabolically healthy obesity, phenotype 4 — metabolically unhealthy obesity.RESULTS: 2352 participants of KYH were included in the study, 982 (41,8%) men and 1370 (58,3%) women. Mean age was 53,9 (SD 9,7) years. The distribution of participants by metabolic phenotypes was as follows: 1167 (49,6%) persons had phenotype 1, 489 (20,8%) — phenotype 2, 248 (10,5%) — phenotype 3, 448 (19,1%) — phenotype 4. In men, the second common after the first phenotype was phenotype 2, while in women, the second position was shared by the 2nd and 4th phenotypes, which had approximately the same frequency. «Arterial hypertension» was the most prevalent component of metabolic syndrome and seen in 68–96% men and 38–94% women in the study with different phenotypes. The proportions of phenotypes with metabolic disorders increased with age.CONCLUSION: in a study of a random population sample within the framework of the concept of metabolic phenotypes, a half of the participants had no obesity and metabolic syndrome. Proportions of participants with metabolic disorders with and without obesity was 20% each. Only 10% of participants had «metabolically healthy» obesity. If excluding individuals without obesity and metabolic syndrome, the phenotype characterized by metabolic disorders in the absence of obesity was the most common among men. Phenotypes with metabolic disorders on the background of obesity or without obesity were equally common among women. The most common component of metabolic syndrome was «arterial hypertension». There was a tendency of accumulation of metabolic disturbances with age

Search for an exotic three-body decay of orthopositronium

We report on a direct search for a three-body decay of the orthopositronium into a photon and two penetrating particles, o-Ps -> gamma + X1 + X2. The existence of this decay could explain the discrepancy between the measured and the predicted values of the orthopositronium decay rate. From the analysis of the collected data a single candidate event is found, consistent with the expected background. This allows to set an upper limit on the branching ratio < 4.4 \times 10^{-5} (at the 90% confidence level), for the photon energy in the range from 40 keV < E_gamma< 400 keV and for mass values in the kinematical range 0 gamma + X1 + X2 decay mode as the origin of the discrepancy.Comment: 9 pages, 3 figure

A new measurement of the properties of the rare decay K -> pi+ e+ e-

A large low-background sample of events (10300) has been collected for the rare decay of kaons in flight K+ -> pi+ e+ e- by experiment E865 at the Brookhaven AGS. The decay products were accepted by a broad band high-resolution charged particle spectrometer with particle identification. The branching ratio (2.94 +- 0.05(stat.) +- 0.13(syst.) +- 0.05(model))*10**{-7} was determined normalizing to events from the decay chain K+ -> pi+ pi0; pi0 -> e+ e- gamma. From the analysis of the decay distributions the vector nature of this decay is firmly established now, and limits on scalar and tensor contributions are deduced. From the (e+ e-) invariant mass distribution the decay form factor f(z)=f0(1+ delta*z) (z=M(ee)**2/m(K)**2) is determined with delta=2.14 +- 0.13 +- 0.15. Chiral QCD perturbation theory predictions for the form factor are also tested, and terms beyond leading order O(p**4) are found to be important.Comment: 4 pages, 5 figure

Performance of the CMS Cathode Strip Chambers with Cosmic Rays

The Cathode Strip Chambers (CSCs) constitute the primary muon tracking device in the CMS endcaps. Their performance has been evaluated using data taken during a cosmic ray run in fall 2008. Measured noise levels are low, with the number of noisy channels well below 1%. Coordinate resolution was measured for all types of chambers, and fall in the range 47 microns to 243 microns. The efficiencies for local charged track triggers, for hit and for segments reconstruction were measured, and are above 99%. The timing resolution per layer is approximately 5 ns

Study of the K- -> pi0 e- nu decay

The decay K- -> pi0 e- nu has been studied using in-flight decays detected with "ISTRA+" setup operating at the 25 GeV negative secondary beam of the U-70 PS. About 130K events were used for the analysis. The lambda_+ parameter of the vector formfactor has been measured: lambda_+ = 0.0293 +- 0.0015(stat) +- 0.002(syst). The limits on the possible tensor and scalar couplings have been derived: f_T/f_+(0)=-0.044 +0.059 -0.057 (stat) f_S/f_+(0)=-0.020 +0.025 -0.016 (stat)Comment: 11 pages, Latex, 9 picture

Performance and Operation of the CMS Electromagnetic Calorimeter

The operation and general performance of the CMS electromagnetic calorimeter using cosmic-ray muons are described. These muons were recorded after the closure of the CMS detector in late 2008. The calorimeter is made of lead tungstate crystals and the overall status of the 75848 channels corresponding to the barrel and endcap detectors is reported. The stability of crucial operational parameters, such as high voltage, temperature and electronic noise, is summarised and the performance of the light monitoring system is presented

Seroprevalence of SARS-Cov-2 Antibodies in Adults, Arkhangelsk, Russia.

Population-based data on coronavirus disease in Russia and on the immunogenicity of the Sputnik V vaccine are sparse. In a survey of 1,080 residents of Arkhangelsk 40-75 years of age, 65% were seropositive for IgG. Fifteen percent of participants had been vaccinated; of those, 97% were seropositive