Last data update: Aug 15, 2025. (Total: 49733 publications since 2009)
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| Query Trace: Iachan R[original query] |
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| Survey Enthusiast or Obligated Responder: Segmenting the Population Based on Government Survey Attitudes
ZuWallack R , Boyle J , Dayton J , Iachan R , Jans M . Int J Public Opin Res 2025 37 (3) This paper explores population segments that differentiate people based on attitudes and perceptions about surveys and how those segments differ in survey participation intention. Our analysis finds 5 population segments across which general affinity toward surveys differs significantly. Survey Enthusiasts have high affinity toward surveys and underlying sense of civic responsibility to participate. Obligated Responders recognize the importance of participating, yet view surveys as an imposition. Reluctant Responders recognize survey participation as important but are moderately concerned about data misuse. The remaining 2 segments, the Disengaged and Shy Responders, have low affinities for survey participation. These findings suggest that effective survey designs should tailor different appeals and protocols to the motivations of a heterogeneous population. A multidimensional approach would parallel those approaches used in marketing where product differentiation and market segmentation help to successfully reach the consumer market. © 2025 The Author(s). Published by Oxford University Press on behalf of The World Association for Public Opinion Research. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site - for further information please contact journals.permissions@oup.com. |
| Ratio of infections to COVID-19 cases and hospitalizations in the United States based on SARS-CoV-2 seroprevalence data, September 2021-February 2022
Deng Y , Kim Y , Bratcher A , Jones JM , Simuzingili M , Gundlapalli AV , Hagen MB , Iachan R , Clarke KEN . Open Forum Infect Dis 2025 12 (1) ofae719
BACKGROUND: Understanding the risk of hospitalization from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections can guide effective public health interventions and severity assessments. This study calculated infection-hospitalization ratios (IHRs) and infection-case ratios (ICRs) to understand the relationship between SARS-CoV-2 infections, cases, and hospitalizations among different age groups during periods of Delta and Omicron variant predominance. METHODS: After calculating antinucleocapsid SARS-CoV-2 antibody seroprevalence using residual commercial laboratory serum specimens, 2 ratios were computed: (1) IHRs using coronavirus disease 2019 hospitalization data and (2) ICRs using Centers for Disease Control and Prevention surveillance data. Ratios were calculated across age groups (0-17, 18-49, 50-69, and ≥70 years) for 2 time periods (September-December 2021 [Delta] and December 2021-February 2022 [Omicron]). RESULTS: Pediatric IHRs increased from 76.7 during Delta to 258.4 during Omicron. Adult IHRs ranged from 3.0 (≥70 years) to 21.6 (18-49 years) during Delta and from 10.0 (≥70 years) to 119.1 (18-49 years) during Omicron. The pediatric ICR was lower during the Delta period (2.7) compared with the Omicron period (3.7). Adult ICRs (Delta: 1.1 [18-49 years] to 2.1 [70+ years]; Omicron: 2.2 [>70+ years] to 2.9 [50-69 years]) were lower than pediatric ICRs during both time periods. CONCLUSIONS: All age groups exhibited a lower proportion of infections associated with hospitalization in the Omicron period than the Delta period; the proportion of infections associated with hospitalization increased with each older age group. A lower proportion of SARS-CoV-2 infections were associated with reported cases in the Omicron period than in the Delta period among all age groups. |
| School mask policies and SARS-CoV-2 seroprevalence among school-age children-United States, September to December 2021
Nycz E , Deng Y , Van Dyke ME , Bratcher A , Shi J , Iachan R , Berney K , Jones JM , Clarke KEN . Microbiol Spectr 2024 e0069124 During September to December 2021, school mask policies to mitigate SARS-CoV-2 transmission varied throughout the US. We compared infection-induced seroprevalence estimates and estimated seroconversion among children residing in areas with and without school mask requirements. We estimated infection-induced seroprevalence among children in three age groups (5-17, 5-11, and 12-17 years) in areas with and without school district mask requirements for two time points: September 1-30, 2021 and December 15, 2021 to January 14, 2022. Robust Poisson regression models estimated population seroconversion over the semester among initially seronegative children. Permutation tests assessed for significant differences in the estimated population seroconversion due to incident infections by school district mask policy. Residing in an area with no school mask requirement was associated with higher infection-induced seroprevalence among children aged 5-17 years (adjusted prevalence ratio [aPR] = 1.18, 95% confidence interval [CI]: 1.10, 1.26), and those aged 5-11 years (aPR) = 1.21, 95% CI: 1.10, 1.32) and those aged 12-17 years (aPR = 1.16, 95% CI: 1.07, 1.26), compared with areas requiring masks in school. Estimated population seroconversion during the semester was also significantly higher among children in districts without mask policies than those with school mask requirements among all age groups (5-17 years: 23.7% vs 18.1%, P < 0.001; 5-11 years: 6.4% vs 4.5%, P = 0.002;12-17 years: 27.2% vs 21.0%, P < 0.001). During the U.S. Fall 2021 semester, areas with school mask requirements had lower infection-induced seroprevalence and an estimated lower proportion of seroconversion due to incident infection among school-aged children compared with areas without school mask requirements; causality cannot necessarily be inferred from these associations. IMPORTANCE: During the U.S. Fall 2021 school semester, the estimated proportion of previously uninfected school-aged children who experienced a first infection with SARS-CoV-2 was lower in areas where public school district policies required masks for all staff and students compared with areas where the school districts had no mask requirements. Because children are more likely than adults to experience asymptomatic or mild SARS-CoV-2 infections, the presence of infection-induced antibodies is a more accurate measure of infection history than clinical testing. The proportion of children with these antibodies (i.e., seroprevalence) can improve our understanding of SARS-CoV-2 by detecting more infections and eliminating potential bias due to local testing and reporting practices. Enhanced robustness of surveillance for respiratory infections in children, including records of mitigation policies in communities and schools, as well as seroprevalence data, would establish a better evidence base for policy decisions and response measures during future respiratory outbreaks. |
| Disparities in the implementation of school-based mental health supports among K-12 public schools
Moore S , Timpe Z , Rasberry CN , Hertz M , Verlenden J , Spencer P , Murray C , Lee S , Barrios LC , Tripathi T , McConnell L , Iachan R , Pampati S . Psychiatr Serv 2023 75 (1) appips20220558 OBJECTIVE: The authors sought to explore the availability of mental health supports within public schools during the COVID-19 pandemic by using survey data from a nationally representative sample of U.S. K-12 public schools collected in October-November 2021. METHODS: The prevalence of 11 school-based mental health supports was examined within the sample (N=437 schools). Chi-square tests and adjusted logistic regression models were used to identify associations between school-level characteristics and mental health supports. School characteristics included level (elementary, middle, or high school), locale (city, town, suburb, or rural area), poverty level, having a full-time school nurse, and having a school-based health center. RESULTS: Universal mental health programs were more prevalent than more individualized and group-based supports (e.g., therapy groups); however, prevalence of certain mental health supports was low among schools (e.g., only 53% implemented schoolwide trauma-informed practices). Schools having middle to high levels of poverty or located in rural areas or towns and elementary schools and schools without a health infrastructure were less likely to implement mental health supports, even after analyses were adjusted for school-level characteristics. For example, compared with low-poverty schools, mid-poverty schools had lower odds of implementing prosocial skills training for students (adjusted OR [AOR]=0.49, 95% CI=0.27-0.88) and providing confidential mental health screening (AOR=0.42, 95% CI=0.22-0.79). CONCLUSIONS: Implementation levels of school-based mental health supports leave substantial room for improvement, and numerous disparities existed by school characteristics. Higher-poverty areas, schools in rural areas or towns, and elementary schools and schools without a health infrastructure may require assistance in ensuring equitable access to mental health supports. |
| Disparities in implementing COVID-19 prevention strategies in public schools, United States, 2021-22 school year
Pampati S , Rasberry CN , Timpe Z , McConnell L , Moore S , Spencer P , Lee S , Murray CC , Adkins SH , Conklin S , Deng X , Iachan R , Tripathi T , Barrios LC . Emerg Infect Dis 2023 29 (5) 937-944 During the COVID-19 pandemic, US schools have been encouraged to take a layered approach to prevention, incorporating multiple strategies to curb transmission of SARS-CoV-2. Using survey data representative of US public K-12 schools (N = 437), we determined prevalence estimates of COVID-19 prevention strategies early in the 2021-22 school year and describe disparities in implementing strategies by school characteristics. Prevalence of prevention strategies ranged from 9.3% (offered COVID-19 screening testing to students and staff) to 95.1% (had a school-based system to report COVID-19 outcomes). Schools with a full-time school nurse or school-based health center had significantly higher odds of implementing several strategies, including those related to COVID-19 vaccination. We identified additional disparities in prevalence of strategies by locale, school level, and poverty. Advancing school health workforce and infrastructure, ensuring schools use available COVID-19 funding effectively, and promoting efforts in schools with the lowest prevalence of infection prevention strategies are needed for pandemic preparedness. |
| Challenges experienced by U.S. K-12 public schools in serving students with special education needs or underlying health conditions during the COVID-19 pandemic and strategies for improved accessibility
Spencer P , Timpe Z , Verlenden J , Rasberry CN , Moore S , Yeargin-Allsopp M , Claussen AH , Lee S , Murray C , Tripathi T , Conklin S , Iachan R , McConnell L , Deng X , Pampati S . Disabil Health J 2022 101428 BACKGROUND: Students with special education needs or underlying health conditions have been disproportionately impacted (e.g., by reduced access to services) throughout the COVID-19 pandemic. OBJECTIVE: This study describes challenges reported by schools in providing services and supports to students with special education needs or underlying health conditions and describes schools' use of accessible communication strategies for COVID-19 prevention. METHODS: This study analyzes survey data from a nationally representative sample of U.S. K-12 public schools (n=420, February-March 2022). Weighted prevalence estimates of challenges in serving students with special education needs or underlying health conditions and use of accessible communication strategies are presented. Differences by school locale (city/suburb vs. town/rural) are examined using chi-square tests. RESULTS: The two most frequently reported school-based challenges were staff shortages (51.3%) and student compliance with prevention strategies (32.4%), and the two most frequently reported home-based challenges were the lack of learning partners at home (25.5%) and lack of digital literacy among students' families (21.4%). A minority of schools reported using accessible communications strategies for COVID-19 prevention efforts, such as low-literacy materials (7.3%) and transcripts that accompany podcasts or videos (6.7%). Town/rural schools were more likely to report non-existent or insufficient access to the internet at home and less likely to report use of certain accessible communication than city/suburb schools. CONCLUSION: Schools might need additional supports to address challenges in serving students with special education needs or with underlying health conditions and improve use of accessible communication strategies for COVID-19 and other infectious disease prevention. |
| Estimated SARS-CoV-2 antibody seroprevalence trends and relationship to reported case prevalence from a repeated, cross-sectional study in the 50 states and the District of Columbia, United States-October 25, 2020-February 26, 2022.
Wiegand RE , Deng Y , Deng X , Lee A , Meyer WA3rd , Letovsky S , Charles MD , Gundlapalli AV , MacNeil A , Hall AJ , Thornburg NJ , Jones J , Iachan R , Clarke KEN . Lancet Reg Health Am 2023 18 100403 BACKGROUND: Sero-surveillance of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can reveal trends and differences in subgroups and capture undetected or unreported infections that are not included in case-based surveillance systems. METHODS: Cross-sectional, convenience samples of remnant sera from clinical laboratories from 51 U.S. jurisdictions were assayed for infection-induced SARS-CoV-2 antibodies biweekly from October 25, 2020, to July 11, 2021, and monthly from September 6, 2021, to February 26, 2022. Test results were analyzed for trends in infection-induced, nucleocapsid-protein seroprevalence using mixed effects models that adjusted for demographic variables and assay type. FINDINGS: Analyses of 1,469,792 serum specimens revealed U.S. infection-induced SARS-CoV-2 seroprevalence increased from 8.0% (95% confidence interval (CI): 7.9%-8.1%) in November 2020 to 58.2% (CI: 57.4%-58.9%) in February 2022. The U.S. ratio of the change in estimated seroprevalence to the change in reported case prevalence was 2.8 (CI: 2.8-2.9) during winter 2020-2021, 2.3 (CI: 2.0-2.5) during summer 2021, and 3.1 (CI: 3.0-3.3) during winter 2021-2022. Change in seroprevalence to change in case prevalence ratios ranged from 2.6 (CI: 2.3-2.8) to 3.5 (CI: 3.3-3.7) by region in winter 2021-2022. INTERPRETATION: Ratios of the change in seroprevalence to the change in case prevalence suggest a high proportion of infections were not detected by case-based surveillance during periods of increased transmission. The largest increases in the seroprevalence to case prevalence ratios coincided with the spread of the B.1.1.529 (Omicron) variant and with increased accessibility of home testing. Ratios varied by region and season with the highest ratios in the midwestern and southern United States during winter 2021-2022. Our results demonstrate that reported case counts did not fully capture differing underlying infection rates and demonstrate the value of sero-surveillance in understanding the full burden of infection. Levels of infection-induced antibody seroprevalence, particularly spikes during periods of increased transmission, are important to contextualize vaccine effectiveness data as the susceptibility to infection of the U.S. population changes. FUNDING: This work was supported by the Centers for Disease Control and Prevention, Atlanta, Georgia. |
| Pediatric Infection-Induced SARS-CoV-2 Seroprevalence Increases and Seroprevalence by Type of Clinical Care-September 2021-February 2022.
Clarke KEN , Kim Y , Jones J , Lee A , Deng Y , Nycz E , Iachan R , Gundlapalli AV , MacNeil A , Hall A . J Infect Dis 2022 227 (3) 364-370 BACKGROUND AND OBJECTIVES: Trends in estimates of US pediatric SARS-CoV-2 infection-induced seroprevalence from commercial laboratory specimens may overrepresent children with frequent healthcare needs. We examined seroprevalence trends and compared seroprevalence estimates by testing type and diagnostic coding. METHODS: Cross-sectional convenience samples of residual sera between September 2021 and February 2022 from 52 U.S. jurisdictions were assayed for infection-induced SARS-CoV-2 antibodies; monthly seroprevalence estimates were calculated by age group. Multivariate logistic analyses compared seroprevalence estimates for specimens associated with ICD-10 codes and laboratory orders indicating well-child care with estimates for other pediatric specimens. RESULTS: Infection-induced SARS-CoV-2 seroprevalence increased in each age group; from 30% to 68% (1-4 years), 38% to 77% (5-11 years), and 40% to 74% (12-17 years). On multivariate analysis, patients with well-child ICD-10 codes were seropositive more often than other patients aged 1-17 years (adjusted prevalence ratio [aPR] 1.04; 95% CI 1.02-1.07); children aged 9-11 years receiving standard lipid screening were seropositive more often than those receiving other laboratory tests (1.05; 1.02-1.08). CONCLUSIONS: Infection-induced seroprevalence more than doubled among children under 12 between September 2021 and February 2022, and increased 85% in adolescents. Differences in seroprevalence by care type did not substantially impact US pediatric seroprevalence estimates. |
| Ventilation Improvement Strategies Among K-12 Public Schools - The National School COVID-19 Prevention Study, United States, February 14-March 27, 2022.
Pampati S , Rasberry CN , McConnell L , Timpe Z , Lee S , Spencer P , Moore S , Mead KR , Murray CC , Deng X , Iachan R , Tripathi T , Martin SBJr , Barrios LC . MMWR Morb Mortal Wkly Rep 2022 71 (23) 770-775 Effective COVID-19 prevention in kindergarten through grade 12 (K-12) schools requires multicomponent prevention strategies in school buildings and school-based transportation, including improving ventilation (1). Improved ventilation can reduce the concentration of infectious aerosols and duration of potential exposures (2,3), is linked to lower COVID-19 incidence (4), and can offer other health-related benefits (e.g., better measures of respiratory health, such as reduced allergy symptoms) (5). Whereas ambient wind currents effectively dissipate SARS-CoV-2 (the virus that causes COVID-19) outdoors,* ventilation systems provide protective airflow and filtration indoors (6). CDC examined reported ventilation improvement strategies among a nationally representative sample of K-12 public schools in the United States using wave 4 (February 14-March 27, 2022) data from the National School COVID-19 Prevention Study (NSCPS) (420 schools), a web-based survey administered to school-level administrators beginning in summer 2021.(†) The most frequently reported ventilation improvement strategies were lower-cost strategies, including relocating activities outdoors (73.6%), inspecting and validating existing heating, ventilation and air conditioning (HVAC) systems (70.5%), and opening doors (67.3%) or windows (67.2%) when safe to do so. A smaller proportion of schools reported more resource-intensive strategies such as replacing or upgrading HVAC systems (38.5%) or using high-efficiency particulate air (HEPA) filtration systems in classrooms (28.2%) or eating areas (29.8%). Rural and mid-poverty-level schools were less likely to report several resource-intensive strategies. For example, rural schools were less likely to use portable HEPA filtration systems in classrooms (15.6%) than were city (37.7%) and suburban schools (32.9%), and mid-poverty-level schools were less likely than were high-poverty-level schools to have replaced or upgraded HVAC systems (32.4% versus 48.8%). Substantial federal resources to improve ventilation in schools are available.(§) Ensuring their use might reduce SARS-CoV-2 transmission in schools. Focusing support on schools least likely to have resource-intensive ventilation strategies might facilitate equitable implementation of ventilation improvements. |
| Seroprevalence of Infection-Induced SARS-CoV-2 Antibodies - United States, September 2021-February 2022.
Clarke KEN , Jones JM , Deng Y , Nycz E , Lee A , Iachan R , Gundlapalli AV , Hall AJ , MacNeil A . MMWR Morb Mortal Wkly Rep 2022 71 (17) 606-608 In December 2021, the B.1.1.529 (Omicron) variant of SARS-CoV-2, the virus that causes COVID-19, became predominant in the United States. Subsequently, national COVID-19 case rates peaked at their highest recorded levels.* Traditional methods of disease surveillance do not capture all COVID-19 cases because some are asymptomatic, not diagnosed, or not reported; therefore, the proportion of the population with SARS-CoV-2 antibodies (i.e., seroprevalence) can improve understanding of population-level incidence of COVID-19. This report uses data from CDC's national commercial laboratory seroprevalence study and the 2018 American Community Survey to examine U.S. trends in infection-induced SARS-CoV-2 seroprevalence during September 2021-February 2022, by age group. |
| Changes to the sample design and weighting methods of a public health surveillance system to also include persons not receiving HIV medical care
Johnson CH , Beer L , Harding RL , Iachan R , Moyse D , Lee A , Kyle T , Chowdhury PP , Shouse RL . PLoS One 2020 15 (12) e0243351 OBJECTIVES: The Medical Monitoring Project (MMP) is a public health surveillance system that provides representative estimates of the experiences and behaviors of adults with diagnosed HIV in the United States. In 2015, the sample design and frame of MMP changed from a system that only included HIV patients to one that captures the experiences of persons receiving and not receiving HIV care. We describe methods investigated for calculating survey weights, the approach chosen, and the benefits of using a dynamic surveillance registry as a sampling frame. METHODS: MMP samples adults with diagnosed HIV from the National HIV Surveillance System, the HIV case surveillance registry for the United States. In the methodological study presented in this manuscript, we compared methods that account for sample design and nonresponse, including weighting class adjustment vs. propensity weighting and a single-stage nonresponse adjustment vs. sequential adjustments for noncontact and nonresponse. We investigated how best to adjust for non-coverage using surveillance data to post-stratify estimates. RESULTS: After assessing these methods, we chose as our preferred procedure weighting class adjustments and a single-stage nonresponse adjustment. Classes were constructed using variables associated with respondents' characteristics and important survey outcomes, chief among them laboratory results available from surveillance that served as a proxy for medical care. CONCLUSIONS: MMPs weighting procedures reduced sample bias by leveraging auxiliary information on medical care available from the surveillance registry sampling frame. Expanding MMPs population of focus provides important information on characteristics of persons with diagnosed HIV that complement the information provided by the surveillance registry. MMP methods can be applied to other disease registries or population-monitoring systems when more detailed information is needed for a population, with the detailed information obtained efficiently from a representative sample of the population covered by the registry. |
| Estimated SARS-CoV-2 Seroprevalence in the US as of September 2020.
Bajema KL , Wiegand RE , Cuffe K , Patel SV , Iachan R , Lim T , Lee A , Moyse D , Havers FP , Harding L , Fry AM , Hall AJ , Martin K , Biel M , Deng Y , Meyer WA3rd , Mathur M , Kyle T , Gundlapalli AV , Thornburg NJ , Petersen LR , Edens C . JAMA Intern Med 2020 181 (4) 450-460 IMPORTANCE: Case-based surveillance of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection likely underestimates the true prevalence of infections. Large-scale seroprevalence surveys can better estimate infection across many geographic regions. OBJECTIVE: To estimate the prevalence of persons with SARS-CoV-2 antibodies using residual sera from commercial laboratories across the US and assess changes over time. DESIGN, SETTING, AND PARTICIPANTS: This repeated, cross-sectional study conducted across all 50 states, the District of Columbia, and Puerto Rico used a convenience sample of residual serum specimens provided by persons of all ages that were originally submitted for routine screening or clinical management from 2 private clinical commercial laboratories. Samples were obtained during 4 collection periods: July 27 to August 13, August 10 to August 27, August 24 to September 10, and September 7 to September 24, 2020. EXPOSURES: Infection with SARS-CoV-2. MAIN OUTCOMES AND MEASURES: The proportion of persons previously infected with SARS-CoV-2 as measured by the presence of antibodies to SARS-CoV-2 by 1 of 3 chemiluminescent immunoassays. Iterative poststratification was used to adjust seroprevalence estimates to the demographic profile and urbanicity of each jurisdiction. Seroprevalence was estimated by jurisdiction, sex, age group (0-17, 18-49, 50-64, and ≥65 years), and metropolitan/nonmetropolitan status. RESULTS: Of 177 919 serum samples tested, 103 771 (58.3%) were from women, 26 716 (15.0%) from persons 17 years or younger, 47 513 (26.7%) from persons 65 years or older, and 26 290 (14.8%) from individuals living in nonmetropolitan areas. Jurisdiction-level seroprevalence over 4 collection periods ranged from less than 1% to 23%. In 42 of 49 jurisdictions with sufficient samples to estimate seroprevalence across all periods, fewer than 10% of people had detectable SARS-CoV-2 antibodies. Seroprevalence estimates varied between sexes, across age groups, and between metropolitan/nonmetropolitan areas. Changes from period 1 to 4 were less than 7 percentage points in all jurisdictions and varied across sites. CONCLUSIONS AND RELEVANCE: This cross-sectional study found that as of September 2020, most persons in the US did not have serologic evidence of previous SARS-CoV-2 infection, although prevalence varied widely by jurisdiction. Biweekly nationwide testing of commercial clinical laboratory sera can play an important role in helping track the spread of SARS-CoV-2 in the US. |
| Teacher physical education practices and student outcomes in a sample of middle schools participating in the Presidential Youth Fitness Program
Lucas IR , Harris C , Lee S , Wargo J , Barnes SP , Kauh TJ , Iachan R . Prev Chronic Dis 2019 16 E104 Obesity and lack of physical activity among children and adolescents are public health problems in the United States. This Presidential Youth Fitness Program (PYFP) evaluation measured program implementation in 13 middle schools and its effect on physical education practices, student fitness knowledge, and student physical activity and fitness levels. PYFP, a free program with the potential to positively affect student health and fitness outcomes, was designed to improve fitness education practices that are easily integrated into existing physical education programs. We used a 2-group (13 PYFP and 13 comparison schools) quasi-experimental design to collect FitnessGram assessments, accelerometry data, and surveys of students, physical education teachers, and administrators. Although the program was positively associated with student cardiovascular endurance and physical activity gains during the semester, schools underused professional development courses and fitness recognition resources. |
| National weighting of data from the Behavioral Risk Factor Surveillance System (BRFSS)
Iachan R , Pierannunzi C , Healey K , Greenlund KJ , Town M . BMC Med Res Methodol 2016 16 (1) 155 BACKGROUND: The Behavioral Risk Factor Surveillance System (BRFSS) is a network of health-related telephone surveys--conducted by all 50 states, the District of Columbia, and participating US territories-that receive technical assistance from CDC. Data users often aggregate BRFSS state samples for national estimates without accounting for state-level sampling, a practice that could introduce bias because the weighted distributions of the state samples do not always adhere to national demographic distributions. METHODS: This article examines six methods of reweighting, which are then compared with key health indicator estimates from the National Health Interview Survey (NHIS) based on 2013 data. RESULTS: Compared to the usual stacking approach, all of the six new methods reduce the variance of weights and design effect at the national level, and some also reduce the estimated bias. This article also provides a comparison of the methods based on the variances induced by unequal weighting as well as the bias reduction induced by raking at the national level, and recommends a preferred method. CONCLUSIONS: The new method leads to weighted distributions that more accurately reproduce national demographic characteristics. While the empirical results for key estimates were limited to a few health indicators, they also suggest reduction in potential bias and mean squared error. To the extent that survey outcomes are associated with these demographic characteristics, matching the national distributions will reduce bias in estimates of these outcomes at the national level. |
| Design and weighting methods for a nationally representative sample of HIV-infected adults receiving medical care in the United States - Medical Monitoring Project
Iachan R , Johnson C H , Harding R L , Kyle T , Saavedra P , Frazier E L , Beer L , Mattson C L , Skarbinski J . Open AIDS J 2016 10 164-81 BACKGROUND: Health surveys of the general US population are inadequate for monitoring human immunodeficiency virus (HIV) infection because the relatively low prevalence of the disease (<0.5%) leads to small subpopulation sample sizes. OBJECTIVE: To collect a nationally and locally representative probability sample of HIV-infected adults receiving medical care to monitor clinical and behavioral outcomes, supplementing the data in the National HIV Surveillance System. This paper describes the sample design and weighting methods for the Medical Monitoring Project (MMP) and provides estimates of the size and characteristics of this population. METHODS: To develop a method for obtaining valid, representative estimates of the in-care population, we implemented a cross-sectional, three-stage design that sampled 23 jurisdictions, then 691 facilities, then 9,344 HIV patients receiving medical care, using probability-proportional-to-size methods. The data weighting process followed standard methods, accounting for the probabilities of selection at each stage and adjusting for nonresponse and multiplicity. Nonresponse adjustments accounted for differing response at both facility and patient levels. Multiplicity adjustments accounted for visits to more than one HIV care facility. RESULTS: MMP used a multistage stratified probability sampling design that was approximately self-weighting in each of the 23 project areas and nationally. The probability sample represents the estimated 421,186 HIV-infected adults receiving medical care during January through April 2009. Methods were efficient (i.e., induced small, unequal weighting effects and small standard errors for a range of weighted estimates). CONCLUSION: The information collected through MMP allows monitoring trends in clinical and behavioral outcomes and informs resource allocation for treatment and prevention activities. |
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