A deviation bar chart for detecting dengue outbreaks in Puerto Rico.
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OBJECTIVES: A Centers for Disease Control and Prevention deviation bar chart (Statistical Software for Public Health Surveillance) and laboratory-based surveillance data were evaluated for their utility in detecting dengue outbreaks in Puerto Rico. METHODS: A significant increase in dengue incidence was defined as an excess of suspected cases of more than 2 SDs beyond the mean for all 4-week periods from April through June (the period of lowest seasonal incidence), 1989 through 1993. An outbreak was defined as a cumulative annual rate of reported dengue greater than 3 per 1000 population. RESULTS: Retrospective application of the system to 1994 data showed agreement with previous analyses. In 1995 and 1996, 36.4% and 27.3%, respectively, of municipalities with a significant increase in reports for 2 or more consecutive weeks before the first week of September had an outbreak, compared with 9.0% (in 1995, P = .042) and 6.0% (in 1996, P = .054) of towns without a significant increase. The system showed sensitivity near 40%, specificity near 89%, and accuracy in classifying municipalities near 84%. CONCLUSIONS: This method provides a statistically based, visually striking, specific, and timely signal for dengue control efforts. (+info)
What are minimal important changes for asthma measures in a clinical trial?
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In this study, the perceptions of asthmatics to change in their disease was associated with observed changes in clinical asthma measures, in order to identify the threshold where changes in clinical asthma measures are perceivable by patients. The study included 281 asthmatic patients, aged 18-63 yrs, in a randomized, placebo-controlled clinical trial of a leukotriene antagonist. Changes were related in: 1) asthma symptom scores; 2) inhaled beta-agonist use; 3) forced expiratory volume in one second (FEV1); and 4) peak expiratory flow (PEF) to a global question that queried overall change in asthma since starting the study drug. Additional analyses examined differences in the group reporting minimal improvement by treatment (active treatment versus placebo), sex and age groups. The average minimal patient perceivable improvement for each measure was: 1) -0.31 points for the symptom score on a scale of 0-6; 2) -0.81 puffs x day(-1) for inhaled beta-agonist use; 3) 0.23 L for FEV1; and 4) 18.79 L x min(-1) for PEF. In general placebo-treated patients and older patients, who reported minimal improvement, experienced less mean improvement from baseline than active-treated patients and younger patients, who reported minimal improvement. Determining the minimal patient perceivable improvement value for a measure may be helpful to interpret changes. However, interpretation should be carried out cautiously when reporting a single value as a clinically important change. (+info)
Accessing and using hospital activity data.
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Hospital activity data can be accessed from a variety of sources ranging from hospitals to the Department of Health. These data provide valuable and widely used information, but care is needed in their use and interpretation. Hospital activity rates reflect not only the underlying prevalence and severity of disease, individual factors and referral practices, but also variations related to provider-specific factors: the 'provider effect'. This includes completeness in the data, supply of hospital beds, admission policies, hospital access and distance from hospital. The provider effect can be controlled to a certain extent in statistical analyses. Although data quality has improved considerably in the last decade, this should still be investigated where trusts are being compared and in small area studies because missing data may lead to artefactual differences in rates. 'Dump' postcodes, where missing or unknown postcodes are assigned to a local postcode such as that of the hospital, may affect small area analyses and linkage if a proxy patient identifier is constructed that includes postcode. (+info)
Antimicrobial resistance prevalence rates in hospital antibiograms reflect prevalence rates among pathogens associated with hospital-acquired infections.
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To determine whether routine antibiograms (summaries reporting resistance of all tested isolates) reflect resistance rates among pathogens associated with hospital-acquired infections, we compared data collected from 2 different surveillance components in the same 166 intensive care units (ICUs). ICUs reported data during the same months to both the infection-based surveillance and the laboratory-based surveillance. Paired comparisons of the percentage of isolates resistant were made between systems within each ICU. No significant differences existed (P>.05) between the percentage of isolates resistant from the infection-based system and laboratory-based system for all antimicrobial-resistant organisms studied, except methicillin resistance in Staphylococcus species. The mean difference in percentage resistance was higher from the infection-based system than the laboratory-based system for S. aureus (mean difference, +8%, P<.001) and coagulase-negative staphylococci (mean difference, +9%, P<.001). Overall, hospital antibiograms reflected susceptibility patterns among isolates associated with hospital-acquired infections. Hospital antibiograms may underestimate the relative frequency of methicillin resistance among Staphylococcus species when associated with hospital-acquired infections. (+info)
New considerations in analyzing stroke and heart disease mortality trends: the Year 2000 Age Standard and the International Statistical Classification of Diseases and Related Health Problems, 10th Revision.
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BACKGROUND: Monitoring of trends and patterns of stroke mortality will be of utmost importance in the coming decade. Two innovations in vital statistics may complicate this task and must be brought to the attention of both researchers and readers of research reports: the new Year 2000 Age Standard and the International Statistical Classification of Diseases and Related Health Problems, 10th Revision (ICD-10). SUMMARY OF REVIEW: For cerebrovascular diseases, the age-adjusted death rate is 2.4 times higher with the use of the year 2000 standard than with the use of the old 1940 standard. However, if rates for all years are computed with the use of the same age standard, the percent change from 1979 to 1995 is similar according to the 1940 standard (-35.8%) or the year 2000 standard (-34.3%). Another important effect of the change to the year 2000 standard is to reduce black/white differentials in age-adjusted death rates. Major discontinuities are not observed for mortality trends in cerebrovascular disease or heart disease between International Classification of Diseases, Ninth Revision (ICD-9) (1979-1998) and ICD-10 (1999 and following years) classifications. CONCLUSIONS: All data users must exercise caution to specify the age standard used when assessing or presenting age-adjusted rates over time or between groups. The comparability of ICD codes chosen for years before 1999 versus 1999 or following years must be checked to distinguish changes due to coding from true changes in mortality levels. (+info)
Increasing rural-urban gradients in US suicide mortality, 1970-1997.
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OBJECTIVES: This study examined rural-urban gradients in US suicide mortality and the extent to which such gradients varied across time, sex, and age. METHODS: Using a 10-category rural-urban continuum measure and 1970-1997 county mortality data, we estimated rural-urban differentials in suicide mortality over time by multiple regression and Poisson regression models. RESULTS: Significant rural-urban gradients in age-adjusted male suicide mortality were found in each time period, indicating rising suicide rates with increasing levels of rurality. The gradient increased consistently, suggesting widening rural-urban differentials in male suicides over time. When controlled for geographic variation in divorce rate and ethnic composition, rural men, in each age cohort, had about twice the suicide rate of their most urban counterparts. Observed rural-urban differentials for women diminished over time. In 1995 to 1997, the adjusted suicide rates for young and working-age women were 85% and 22% higher, respectively, in rural than in the most urban areas. CONCLUSIONS: The slope of the relationship between rural-urban continuum and suicide mortality varied substantially by time, sex, and age. Widening rural-urban disparities in suicide may reflect differential changes over time in key social integration indicators. (+info)
Commentary: meta-analysis of individual participants' data in genetic epidemiology.
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The authors summarize their experience in the conduct of meta-analysis of individual participants' data (MIPD) with time-to-event analyses in the field of genetic epidemiology. The MIPD offers many advantages compared with a meta-analysis of the published literature. These include standardization of case definitions, outcomes, and covariates; inclusion of updated information; the ability to fully test the assumptions of time-to-event models; better control of confounding; standardization of analyses of genetic loci that are in linkage disequilibrium; evaluation of alternative genetic models and multiple genes; consistent treatment of subpopulations; assessment of sampling bias; and the establishment of an international collaboration with the capability to prospectively update the meta-analyses and synthesize new information on multiple genetic loci and outcomes. The disadvantages of a MIPD compared with a meta-analysis of the published literature are that a much greater commitment of time and resources is required to collect primary data and to coordinate a large collaborative project. An MIPD may collect additional, unpublished data, but it is possible that not all published data may be contributed at the individual level. For questions that justify the required intensive effort, the MIPD method is a useful tool to help clarify the role of candidate genes in complex human diseases. (+info)
A simple model for potential use with a misclassified binary outcome in epidemiology.
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STUDY OBJECTIVE: Error in determination of disease outcome occurs in epidemiology, but such error is not usually corrected for in statistical analysis. A method of correction of risk estimates for misclassification of a binary disease outcome is developed here. METHODS: The method is a simple, closed form correction to the logistic regression estimate. A closed form variance estimate is also developed. SETTING: The method is illustrated in two studies, a cross sectional survey of cervicitis in Iran in 1996-97, as determined by inflammation on cervical smear specimens, and a case-cohort study of benign proliferative epithelial disease of the breast, in Canada 1980-88. MAIN RESULTS: The method provides corrected odds ratio estimates and corrects the spurious precision conferred by misclassification. CONCLUSIONS: The method is easy to apply and potentially useful, although potential failures of the assumptions involved should be borne in mind. It is necessary to give careful consideration to the plausibility or otherwise of the assumptions in the context of the individual study. Correction for misclassification of disease outcome may become more common with the development of readily applicable methods. (+info)