Device-based physical activity measures for population surveillance-issues of selection bias and reactivity

Background

Device-based measurement in physical activity surveillance is increasing, but research design choices could increase the risk of self-selection bias and reactive behaviour. The aim of this study is to compare the self-reported physical activity profiles of four different samples: participants in a large national survey, participants in a telephone-based survey of non-responders, participants in the large national survey who accepted the invitation to device-based measuring, and the same sample during the week of monitoring.

Methods

In October 2020, 163,133 Danish adults participated in a national survey and of those 39,480 signed up for device-based measurements. A balanced random sample (n = 3,750) was invited to wear an accelerometer of whom 1,525 accepted the invitation. Additionally, a short telephone-based survey on 829 non-responders to the national survey was conducted. Sociodemographic characteristics and self-reported weekly frequencies of physical activity across four domains are compared.

Results

The participants in the national survey were older, more often female, and more often not working. Participants in the telephone-based survey were younger, more often doing unskilled work, and were more often active at home and at work. The participants in the device-based sample were more often active during transport and leisure in the national survey, and participants categorized in the most active category increased during the week of monitoring from 29.0% to 60.7% and from 58.5% to 81.7% for active transport and leisure activities, respectively.

Conclusion

Recruiting a population representative sample for device-based measurement of physical activity is challenging, and there is a substantial risk of sample selection bias and measurement reactivity. Further research in this area is needed if device-based measures should be considered for population physical activity surveillance.

Modeling demersal fish and benthic invertebrate assemblages in support of marine conservation planning

Marine classification schemes based on abiotic surrogates often inform regional marine conservation planning in lieu of detailed biological data. However, these schemes may poorly represent ecologically relevant biological patterns required for effective design and management strategies. We used a community-level modeling approach to characterize and delineate representative mesoscale (tens to thousands of kilometers) assemblages of demersal fish and benthic invertebrates in the Northwest Atlantic. Hierarchical clustering of species occurrence data from four regional annual multispecies trawl surveys revealed three to six groupings (predominant assemblage types) in each survey region, broadly associated with geomorphic and oceanographic features. Indicator analyses identified 3-34 emblematic taxa of each assemblage type. Random forest classifications accurately predicted assemblage distributions from environmental covariates (AUC > 0.95) and identified thermal limits (annual minimum and maximum bottom temperatures) as important predictors of distribution in each region. Using forecasted oceanographic conditions for the year 2075 and a regional classification model, we projected assemblage distributions in the southernmost bioregion (Scotian Shelf-Bay of Fundy) under a high emissions climate scenario (RCP 8.5). Range expansions to the northeast are projected for assemblages associated with warmer and shallower waters of the Western Scotian Shelf over the 21st century as thermal habitat on the relatively cooler Eastern Scotian Shelf becomes more favorable. Community-level modeling provides a biotic-informed approach for identifying broadscale ecological structure required for the design and management of ecologically coherent, representative, well-connected networks of Marine Protected Areas. When combined with oceanographic forecasts, this modeling approach provides a spatial tool for assessing sensitivity and resilience to climate change, which can improve conservation planning, monitoring, and adaptive management.

Evaluation of the Impact of Intratumoral Heterogeneity of Esophageal Cancer on Pathological Diagnosis and P16 Methylation and the Representativity of Endoscopic Biopsy

Background

P16 methylation is expected to be potential diagnostic and therapeutic targets for esophageal cancer (EC). The intratumoral heterogeneity (ITH) of EC has been mentioned but has not been quantitatively measured yet. We aimed to clarify the impact of ITH on pathological diagnosis and P16 methylation, and the concordance between endoscopic biopsy and the corresponding surgically resected tissue.

Methods

We designed a systematic sampling method (SSM) compared with a general sampling method (GSM) to obtain EC tumor tissue, tumor biopsy, and normal squamous epithelium biopsy. MethyLight assay was utilized to test P16 methylation. All specimens obtained by the SSM were pathologically diagnosed.

Results

A total of 81 cases were collected by the GSM, and 91.4% and 8.6% of them were esophageal squamous cell carcinomas (ESCCs) and esophageal adenocarcinomas (EADs), respectively. Nine SSM cases were 100.0% ESCCs. The positive rates of P16 methylation of the GSM tumor and normal tissues were 63.0% (51/81) and 32.1% (26/81), respectively. For SSM samples, tumor tissues were 100.0% (40/40) EC and 85.0% (34/40) P16 methylated; tumor biopsy was 64.4% (29/45) diagnosed of EC and 68.9% P16 methylated; the corresponding normal biopsies were 15.7% (8/51) dysplasia and 54.9% (28/51) P16 methylated. The concordance of pathological diagnosis and P16 methylation between tumor biopsy and the corresponding tumor tissue was 75.0% and 62.5%, respectively.

Conclusion

The SSM we designed was efficient in measuring the ITH of EC. We found inadequate concordance between tumor biopsy and tissue in pathological diagnosis and P16 methylation.

Representing vulnerable populations in genetic studies: The case of the Roma

Moreau () has raised concerns about the use of DNA data obtained from vulnerable populations, such as the Uighurs in China. We discuss another case, situated in Europe and with a research history dating back 100 years: genetic investigations of Roma. In our article, we focus on problems surrounding representativity in these studies. We claim that many of the circa 440 publications in our sample neglect the methodological and conceptual challenges of representativity. Moreover, authors do not account for problematic misrepresentations of Roma resulting from the conceptual frameworks and sampling schemes they use. We question the representation of Roma as a "genetic isolate" and the underlying rationales, with a strong focus on sampling strategies. We discuss our results against the optimistic prognosis that the "new genetics" could help to overcome essentialist understandings of groups.

The reliability of bone marrow cytology as response criterion in metastatic neuroblastoma

BACKGROUND

The quantitative assessment of neuroblastoma cell content in bone marrow aspirates for response evaluation has been introduced recently. Data on the concordance of interobserver reports are lacking so far.

METHODS

Investigators of seven European countries representing national reference or large oncological centers convened in 2016. They agreed to quantitatively assess routine bone marrow smears of the participating institutions and to discuss the discrepant results in joint meetings.

RESULTS

From 2017 through 2019, three cytology rounds with 24, 28, and 28 bone marrow samples were run evaluating the representativity of the smears (yes/[restricted]/no) and the presence of tumor cells (yes/no and %). The comparison of the reports using κ (Fleiss) and α (Krippendorff) statistics demonstrated no robust reliabilities. The agreement on the representativity was moderate to poor, on the presence of tumor cells moderate to good, and on the percentage of tumor cells slight to moderate. Though the value of cytology is unquestioned to detect even tiny metastatic cells in bone marrow, the investigators unanimously agreed that a reliable quantification of the tumor cell content in bone marrow smears is unrealistic. For the key issue of representativity, a new practical definition was developed.

CONCLUSION

For any work with bone marrow aspirates, the representativity of the material is of paramount importance. A practical definition is proposed. A reliable quantitative cytological assessment of tumor cell content in bone marrow aspirates is not feasible in metastatic neuroblastoma. Therefore, its use as response criterion should be reconsidered.

Selection bias in general practice research: analysis in a cohort of pregnant Danish women

OBJECTIVE

The aim of the present study was to examine selection in a general practice-based pregnancy cohort.

DESIGN

Survey linked to administrative register data.

SETTING AND SUBJECTS

In spring 2015, GPs were recruited from two Danish regions. They were asked to invite all pregnant women in their practice who had their first prenatal care visit before 15 August 2016 to participate in the survey.

OUTCOME MEASURES

The characteristics of GPs and the pregnant women were compared at each step in the recruitment process - the GP's invitation, their agreement to participate, actual GP participation, and the women's participation - with an uncertainty coefficient to quantify the step where the largest selection occurs.

RESULTS

Significant differences were found between participating and non-participating practices with regards to practice characteristics such as the number of patients registered with the practice, the age and sex of doctors, and the type of practice. Despite these differences, the characteristics of the eligible patients differed little between participating and non-participating practices. In participating practices significant differences were, however, observed between recruited and non-recruited patients.

CONCLUSION

The skewed selection of patients was mainly caused by a high number of non-participants within practices that actively took part in the study. We recommend that a focus on the sampling within participating practices be the most important factor in representative sampling of patient populations in general practice. Key points Selection among general practitioners (GPs) is often unavoidable in practice-based studies, and we found significant differences between participating and non-participating practices. These include practice characteristics such as the number of GPs, the number of patients registered with the GP practice, as well as the sex and age of the GPs. •Despite this, only small differences in the characteristics of the eligible patients were observed between participating and non-participating practices. •In participating practices, however, significant differences were observed between recruited and non-recruited patients. •Comprehensive sampling within participating practices may be the best way to generate representative samples of patients.

Assessment of representativity of a study population - experience of the Kiel Obesity Prevention Study (KOPS)

OBJECTIVE

Exemplified by data of the Kiel Obesity Prevention Study (KOPS), different methods to control for response bias and to assess representativity were compared.

METHODS

4,997 cross-sectional data of 5- to 7-year-old German children (main cohort) were investigated between 1996 and 2001 within school entry examination. A subgroup responded to a questionnaire to socio-demographic and lifestyle factors (responders, n = 2,631). Representativity of the main cohort was tested in comparison to the total population. To control for response bias within the responders a non-response analysis as well as an analysis of missing values were performed.

RESULTS

The comparison with the total population showed a higher prevalence of obese boys and girls from families of low socio-economic status (SES) within the main cohort. The responders were less frequently obese and overweight and more rarely belonged to low SES families when compared with non-responders. Analysis of missing values did not detect any further biases. According to an epidemiological assessment of differences the main cohort of KOPS is suggested to be representative for all 5- to 7-year-old children in Kiel, whereas the responders can be at best called 'relatively' representative.

CONCLUSION

The analysis of non-response is the most sensitive method to detect group differences, but a comparison with the total population can also be used to control for biases. In addition representativity has to be proven not only for the main cohort but also for the subgroup of responders with which data analysis will be done.