Our research’s breadth lives on convenience samples A case study of the online respondent pool “SoSci Panel”

Convenience samples have been a substantial driver of empirical social research for decades. Undergraduate students are still the researchers’ favorite subjects, but the importance of respondents recruited on the Internet is on the rise. This paper deals with the fuzzy concept of convenience samples, outlining their reasonable uses and limitations. To bolster the theoretical discussion on convenience samples with empirical evidence, findings from the non-commercial SoSci Panel, a large-scale volunteer respondent pool, are presented. Convenience pools allow for larger samples than traditional convenience samples, more heterogeneity, and better long-term availability of respondents. This paper discusses conditions of setting up a respondent pool and methodological and practical implications, such as software, tasks, respondent activity and panel loyalty

Too Fast, too Straight, too Weird: Non-Reactive Indicators for Meaningless Data in Internet Surveys

Practitioners use various indicators to screen for meaningless, careless, or fraudulent responses in Internet surveys. This study employs an experimental-like design to empirically test the ability of non-reactive indicators to identify records with low data quality. Findings suggest that careless responses are most reliably identified by questionnaire completion time, but the tested indicators do not allow for detecting intended faking. The article introduces various indicators, their benefits and drawbacks, proposes a completion speed index for common application in data cleaning, and discusses whether to remove meaningless records at all

Vendor Independent Coronary Calcium Scoring Improves Individual Risk Assessment:The Multi-Ethnic Study of Atherosclerosis (MESA)

BACKGROUND: Substantial variation in Agatston scores (AS) acquired with different computed tomography (CT) scanners may influence patient risk classification.OBJECTIVES: This study sought to develop a calibration tool for state-of-the-art CT systems resulting in vendor-neutral AS (vnAS), and to assess the impact of vnAS on coronary heart disease (CHD) event prediction.METHODS: The vnAS calibration tool was derived by imaging 2 anthropomorphic calcium containing phantoms on 7 different CT and 1 electron beam tomography system, which was used as the reference system. The effect of vnAS on CHD event prediction was analyzed with data from 3,181 participants from MESA (Multi-Ethnic Study on Atherosclerosis). Chi-square analysis was used to compare CHD event rates between low (vnAS &lt;100) and high calcium groups (vnAS ≥100). Multivariable Cox proportional hazard regression models were used to assess the incremental value of vnAS.RESULTS: For all CT systems, a strong correlation with electron beam tomography-AS was found (R 2 &gt;0.932). Of the MESA participants originally in the low calcium group (n = 781), 85 (11%) participants were reclassified to a higher risk category based on the recalculated vnAS. For reclassified participants, the CHD event rate of 15% was significantly higher compared with participants in the low calcium group (7%; P = 0.008) with a CHD HR of 3.39 (95% CI: 1.82-6.35; P = 0.001). CONCLUSIONS: The authors developed a calibration tool that enables calculation of a vnAS. MESA participants who were reclassified to a higher calcium category by means of the vnAS experienced more CHD events, indicating improved risk categorization.</p

The impact of dose reduction on the quantification of coronary artery calcifications and risk categorization:A systematic review

Multiple dose reduction techniques have been introduced for coronary artery calcium (CAC) computed tomography (CT), but few have emerged into clinical practice while an increasing number of patients undergo CAC scanning. We sought to determine to what extend the radiation dose in CAC CT can be safely reduced without a significant impact on cardiovascular disease (CVD) risk stratification. A systematic database-review of articles published from 2002 until February 2018 was performed in Pubmed, WebOfScience, and Embase. Eligible studies reported radiation dose reduction for CAC CT, calcium scores and/or risk stratification for phantom or patient studies. Twenty-eight studies were included, under which 17 patient studies, 10 phantom/ex-vivo studies, and 1 study evaluated both phantom and patients. Dose was reduced with tube voltage reduction and tube current reduction with and without iterative reconstruction (IR), and tin-filter spectral shaping. The different dose reduction techniques resulted in varying final radiation doses and had varying impact on CAC scores and CVD risk stratification. In 78% of the studies the radiation dose was reduced by >= 50% ranging from (CTDIvol) 0.6-5.5 mGy, leading to reclassification rates ranging between 3% and 21%, depending on the acquisition technique. Specific dose reduced protocols, including either tube current reduction and IR or spectral shaping with tin filtration, that showed low reclassification rates may potentially be used in CAC scanning and in future population-based screening for CVD risk stratification

The impact of dose reduction on the quantification of coronary artery calcifications and risk categorization : A systematic review

Multiple dose reduction techniques have been introduced for coronary artery calcium (CAC) computed tomography (CT), but few have emerged into clinical practice while an increasing number of patients undergo CAC scanning. We sought to determine to what extend the radiation dose in CAC CT can be safely reduced without a significant impact on cardiovascular disease (CVD) risk stratification. A systematic database-review of articles published from 2002 until February 2018 was performed in Pubmed, WebOfScience, and Embase. Eligible studies reported radiation dose reduction for CAC CT, calcium scores and/or risk stratification for phantom or patient studies. Twenty-eight studies were included, under which 17 patient studies, 10 phantom/ex-vivo studies, and 1 study evaluated both phantom and patients. Dose was reduced with tube voltage reduction and tube current reduction with and without iterative reconstruction (IR), and tin-filter spectral shaping. The different dose reduction techniques resulted in varying final radiation doses and had varying impact on CAC scores and CVD risk stratification. In 78% of the studies the radiation dose was reduced by ≥ 50% ranging from (CTDIvol) 0.6-5.5 mGy, leading to reclassification rates ranging between 3% and 21%, depending on the acquisition technique. Specific dose reduced protocols, including either tube current reduction and IR or spectral shaping with tin filtration, that showed low reclassification rates may potentially be used in CAC scanning and in future population-based screening for CVD risk stratification

Vendor Independent Coronary Calcium Scoring Improves Individual Risk Assessment:MESA (Multi-Ethnic Study of Atherosclerosis)

Background: Substantial variation in Agatston scores (AS) acquired with different computed tomography (CT) scanners may influence patient risk classification. Objectives: This study sought to develop a calibration tool for state-of-the-art CT systems resulting in vendor-neutral AS (vnAS), and to assess the impact of vnAS on coronary heart disease (CHD) event prediction. Methods: The vnAS calibration tool was derived by imaging 2 anthropomorphic calcium containing phantoms on 7 different CT and 1 electron beam tomography system, which was used as the reference system. The effect of vnAS on CHD event prediction was analyzed with data from 3,181 participants from MESA (Multi-Ethnic Study on Atherosclerosis). Chi-square analysis was used to compare CHD event rates between low (vnAS &lt;100) and high calcium groups (vnAS ≥100). Multivariable Cox proportional hazard regression models were used to assess the incremental value of vnAS. Results: For all CT systems, a strong correlation with electron beam tomography–AS was found (R2 &gt;0.932). Of the MESA participants originally in the low calcium group (n = 781), 85 (11%) participants were reclassified to a higher risk category based on the recalculated vnAS. For reclassified participants, the CHD event rate of 15% was significantly higher compared with participants in the low calcium group (7%; P = 0.008) with a CHD HR of 3.39 (95% CI: 1.82-6.35; P = 0.001). Conclusions: The authors developed a calibration tool that enables calculation of a vnAS. MESA participants who were reclassified to a higher calcium category by means of the vnAS experienced more CHD events, indicating improved risk categorization.</p