Vol 29, No 5 (2022)

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.

BACKGROUND: It is crucial to organize a full-scale epidemic investigation into the rise in connective tissue dysplasia (DCT) among populations in varying climatic zones. Connective tissue dysplasia encourages the emergence and progression of several pathological conditions that harm life quality and length.

AIM: To identify the prevalence and structure of undifferentiated DCT syndrome among teenagers in different climate zones of the Tyumen region.

METHODS: An observational study in the Tyumen region, the Khanty-Mansi Autonomous Okrug-Yugra, the Yamalo-Nenets Autonomous Okrug included 578 teenagers, males, and females main groups (12 and 15 years) from secondary schools and residential schools. The evaluation of phenotypic symptoms for undifferentiated connective tissue dysplasia syndrome was according to recommendations by the Russian medical therapist’s society for diagnostics, treatment, and rehabilitation of people with DCT. The undifferentiated DCT syndrome has relevance, structure, and severity.

RESULTS: The amount of teenagers with undifferentiated DCT syndrome in the Tyumen region is 58.5%. The detection rate of undifferentiated DCT in the Tyumen region (south of the region) is 52.3%, in the Khanty-Mansi Autonomous Okrug-Yugra, it is 61.6%; in the Yamalo-Nenets Autonomous Okrug, 65.3%. Most of the registered phenotypic evidence of DCT included joint hypermobility, spinal scoliosis, hyperkyphosis of the thoracic spine, straight back syndrome, Varga index of 1.5–1.7, asthenic chest, bite anomalies, dysmorphism of the auricles, “Gothic” sky, loose and flabby skin, and myopia. A high average diagnostic coefficient, averaging 35.46±0.05 points, which surpasses the diagnostic threshold by more than two times and indicates possible complications of dysplastic changes. There are no differences in the severity of DCT manifestations according to several prognostically-significant criteria, depending on the climatic and geographical conditions within the studied area.

CONCLUSION: It is very important to take into account the high prevalence and severity of DCT among teenagers in the Tyumen region when planning programs for treatment, prophylactic, and rehabilitation measures.

OBJECTIVE: To assess the impact of non-radiation factors and ionizing radiation on the incidence of liver malignant neoplasms in workers of a nuclear facility.

METHODS: This was a retrospective study that considered a cohort of Mayak PA workers (22,377 individuals hired during 1948–1982 and followed up until 31.12.2018). The analysis included 60 malignant neoplasms of liver that were histologically confirmed. Hazard ratio (HR) and 95% confidence intervals (CI) were estimated in relation to factors under the study using Poisson’s regression.

RESULTS: The risk of total liver malignancies increased with attained age and for individuals with chronic liver diseases — HR=3,59 (95%CI 1,57; 7,21), chronic gallbladder and biliary tract diseases HR=1,83 (95%CI 1,07; 3,11), gallstone disease — HR=2,45 (95%CI 1,15; 4,77). Viral hepatitis elevated the risk of hepatocellular carcinoma (HCC) — HR=7,41 (95%CI 1,20; 24,63). Gallstone disease raised the risk of cholangiocarcinoma (CC) — HR=14,69 (95%CI 3,05; 56,18). Risk of hemangiosarcoma (HAS) was increased in individuals with chronic liver diseases — HR=7,52 (95%CI 1,68; 24,48), and with diseases of the gallbladder and biliary tract — HR=6,01 (95%CI 1,86; 26,88). The risks of total liver malignancies and HAS were found to increase due to external exposure at gamma dose >0,5 Gy and internal exposure at alpha dose of plutonium >1,0 Gy. The risk of HCC increased with alpha dose >4,0 Gy and was not associated with external gamma-ray exposure. The risk of CC increased with gamma-ray exposure at doses >1,0 Gy and was not associated with alpha particle exposure. Among total liver malignancies, the number of HAS was high (26,7%) and among them 68,8% were observed at internal exposure alpha doses >4,0 Gy.

CONCLUSIONS: Incidence of liver malignancies in Mayak PA workers was associated with ionizing radiation, chronic diseases of hepatobiliary tract and viral hepatitis (in case of HCC). To investigate the risk related to occupational radiation exposure, we need to perform a dose-response analysis that will consider non-radiation factors.

BACKGROUND: There was not enough information on the spread of obesity among schoolchildren in rural settlements and small towns of Northern Russia in recent years. This study aimed to trace the prevalence of overweight and obesity in children aged 6–17 years living in rural areas of Northern Russia between 1994 and 2019.

METHODS: Data, including sex, age, body weight, and stature, were collected during regular medical examinations of 7548 children aged 6–17 years living in the rural settlements of Murmansk Oblast, Khanty-Mansi Autonomous Okrug, Komi Republic, Komi-Permyak Okrug in 1994, 1997–1998, 2005–2009, and 2016–2019. Individual assessments were made using body mass indices according to the procedures and cutoffs recommended by the World Health Organization.

RESULTS: The prevalence of excess body weight has substantially increased in all localities. It was 4–7% (including 0.6%–0.8% obesity) in 1994–1998, 7.5–18.7% (obesity 0.9–5.0%) in 2005–2009, and 23.9–26.6% (obesity 7.7–11.9%) in 2016–2019. As 2019 data showed, no difference was found between schoolchildren residing in rural settlements, small towns, large industrial centers, and Moscow.

CONCLUSION: A rapid spread of overweight and obesity among Russian children occurred in the second decade of the 21st century. The northern populations encounter this process in the same degree and extent as others. Geographic (Arctic, non-Arctic North, and Central Russia) and socioeconomic (various levels of urbanization) factors do not play a major role in that negative dynamics.