Influence of sampling on estimates of clustering and recent transmission of Mycobacterium tuberculosis derived from DNA fingerprinting techniques.
The availability of DNA fingerprinting techniques for Mycobacterium tuberculosis has led to attempts to estimate the extent of recent transmission in populations, using the assumption that groups of tuberculosis patients with identical isolates ("clusters") are likely to reflect recently acquired infections. It is never possible to include all cases of tuberculosis in a given population in a study, and the proportion of isolates found to be clustered will depend on the completeness of the sampling. Using stochastic simulation models based on real and hypothetical populations, the authors demonstrate the influence of incomplete sampling on the estimates of clustering obtained. The results show that as the sampling fraction increases, the proportion of isolates identified as clustered also increases and the variance of the estimated proportion clustered decreases. Cluster size is also important: the underestimation of clustering for any given sampling fraction is greater, and the variability in the results obtained is larger, for populations with small clusters than for those with the same number of individuals arranged in large clusters. A considerable amount of caution should be used in interpreting the results of studies on clustering of M. tuberculosis isolates, particularly when sampling fractions are small. (+info)
Elevated hepatic lipase activity and low levels of high density lipoprotein in a normotriglyceridemic, nonobese Turkish population.
Low levels of high density lipoprotein cholesterol (HDL-C) are associated with increased risk of coronary heart disease and, in the United States, are often associated with hypertriglyceridemia and obesity. In Turkey, low HDL-C levels are highly prevalent, 53% of men and 26% of women having HDL-C levels <35 mg/dl, in the absence of hypertriglyceridemia and obesity. In this study to investigate the cause of low HDL-C levels in Turks, various factors affecting HDL metabolism were assessed in normotriglyceridemic Turkish men and women living in Istanbul and in non-Turkish men and women living in San Francisco. Turkish men and women had significantly lower HDL-C levels than the San Francisco men and women, as well as markedly lower apolipoprotein A-I levels (25 and 39 mg/dl lower, respectively). In both Turkish and non-Turkish subjects, the mean body mass index was <27 kg/m2, the mean triglyceride level was <120 mg/dl, and the mean total cholesterol was 170-180 mg/dl. The mean hepatic triglyceride lipase activity was 21% and 31% higher in Turkish men and women, respectively, than in non-Turkish men and women, and remained higher even after subjects with a body mass index >50th percentile for men and women in the United States were excluded from the analysis. As no dietary or behavioral factors have been identified in the Turkish population that account for increased hepatic triglyceride lipase activity, the elevation most likely has a genetic basis. high density lipoprotein in a normotriglyceridemic, nonobese Turkish population. (+info)
Efficacy of Haemophilus influenzae type b conjugate vaccines and persistence of disease in disadvantaged populations. The Haemophilus Influenzae Study Group.
OBJECTIVES: The purpose of this study was to evaluate the effectiveness of Haemophilus influenzae type b (Hib) conjugate vaccines among children aged 2 to 18 months and to determine risk factors for invasive Hib disease during a period of declining incidence (1991-1994). METHODS: A prospective population-based case-control study was conducted in a multistate US population of 15.5 million. A laboratory-based active surveillance system was used for case detection. RESULTS: In a multivariate analysis, having a single-parent mother (odds ratio [OR] = 4.3, 95% confidence interval [CI] = 1.2, 14.8) and household crowding (OR = 3.5, 95% CI = 1.03, 11.7) were risk factors for Hib disease independent of vaccination status. After adjustment for these risk factors, the protective efficacy of 2 or more Hib vaccine doses was 86% (95% CI = 16%, 98%). Among undervaccinated subjects, living with a smoker (P = .02) and several indicators of lower socioeconomic status were risk factors for Hib disease. CONCLUSIONS: Hib disease still occurs at low levels in the United States, predominantly in socioeconomically disadvantaged populations. Low immunization coverage may facilitate continuing transmission of Hib. Special efforts to achieve complete and timely immunization in disadvantaged populations are needed. (+info)
Camelot or common sense? The logic behind the UCSF/Stanford merger.
Many academic medical centers (AMCs) throughout the United States have established their own community-based integrated delivery systems by purchasing physician groups and hospitals. Other AMCs have merged with existing nonprofit community-based delivery systems. Still other AMCs have been sold to for-profit firms. The AMCs at Stanford and the University of California, San Francisco (UCSF), chose a different strategy: to merge with each other to respond to the unique characteristics of the Bay Area marketplace. (+info)
Changes across 3 years in self-reported awareness of product warning messages in a Hispanic community.
This study investigated the self-reported awareness of product warning messages among independent random samples of Hispanics in San Francisco surveyed from 1989 through 1992. Messages tested were primarily related to cigarette smoking and the consumption of alcoholic beverages. In general, respondents reported low levels of awareness of product warning messages with the exception of those messages dealing with the consumption of alcohol or cigarettes during pregnancy. Nevertheless, there were increases in awareness across years for the alcohol-related warning messages and for one of the cigarette messages, indicating that continued exposure increases awareness of the message. A notable proportion of the respondents reported being aware of a bogus message implying the presence of socially desirable responses in self-reports of message awareness. Gender, education, age and acculturation level of the respondents also showed effects on reported awareness of specific messages. Continued exposure to product warning messages seems useful in producing health-enhancing behaviors among Hispanics. (+info)
Characterization of antimicrobial resistance in Streptococcus pyogenes isolates from the San Francisco Bay area of northern California.
During 1994 and 1995, 157 isolates of Streptococcus pyogenes from patients with invasive disease were consecutively collected in the San Francisco Bay area to determine the frequency of antimicrobial resistance. Susceptibility testing was performed according to the guidelines of the National Committee for Clinical Laboratory Standards by the disk method and by broth microdilution. For comparison of susceptibility patterns, an additional 149 strains were randomly collected from patients with pharyngitis. For San Francisco County, 32% of the isolates from invasive-disease-related specimens but only 9% of the isolates from throat cultures from the same period were resistant to erythromycin (P = 0.0007). Alameda County and Contra Costa County had rates of resistance of +info)
Use of pulsed-field gel electrophoresis for molecular epidemiologic and population genetic studies of Mycobacterium tuberculosis.
Pulsed-field gel electrophoresis (PFGE) is a powerful molecular biology technique which has provided important insights into the epidemiology and population biology of many pathogens. However, few studies have used PFGE for the molecular epidemiology of Mycobacterium tuberculosis. A laboratory protocol was developed to determine the typeability, stability, and reproducibility of PFGE typing of M. tuberculosis. Formal data-analytical techniques were used to assess the genetic diversity elucidated by PFGE analyses using four separate restriction enzymes and by IS6110 RFLP analyses, as well as to assess the concordance among these typing methods. One hundred epidemiologically characterized clinical isolates of M. tuberculosis were genotyped with four different PFGE enzymes (AseI, DraI, SpeI, and XbaI), as well as by RFLP analysis with IS6110. Identical patterns were found among 34 isolates known to be genetically related, suggesting that the PFGE protocol is robust and reproducible. Among 66 isolates representing population-sampled cases, heterozygosity and information content dependency estimates indicate that all five genotyping systems capture quantitatively similar levels of genetic diversity. Nevertheless, comparisons between PFGE analyses and IS6110 typing reveals that PFGE provided more discrimination among isolates with fewer than five copies of IS6110 and less clustering in isolates with five or more copies. The comparisons confirm the hypothesis that the resolution of IS6110 RFLP genotyping is dependent upon the number of IS6110 elements in the genome of isolates. The general concordance among the results obtained with four independent enzymes suggests that M. tuberculosis is a clonal organism. The availability of a robust genotyping technique largely independent of repetitive elements has implications for the molecular epidemiology of M. tuberculosis. (+info)
Comparison of methods for classifying Hispanic ethnicity in a population-based cancer registry.
The accuracy of ethnic classification can substantially affect ethnic-specific cancer statistics. In the Greater Bay Area Cancer Registry, which is part of the Surveillance, Epidemiology, and End Results (SEER) Program and of the statewide California Cancer Registry, Hispanic ethnicity is determined by medical record review and by matching to surname lists. This study compared these classification methods with self-report. Ethnic self-identification was obtained by surveying 1,154 area residents aged 20-89 years who were diagnosed with cancer in 1990 and were reported to the registry as being Hispanic or White non-Hispanic. Predictive value positive, sensitivity, and relative bias were used to assess the accuracy of Hispanic classification by medical record and surname. Among those persons classified as Hispanic by either or both of these sources, only two-thirds agreed (predictive value positive = 66%), and many self-identified Hispanics were classified incorrectly (sensitivity = 68%). Classification based on either medical record or surname alone had a lower sensitivity (59% and 61%, respectively) but a higher predictive value positive (77% and 70%, respectively). Ethnic classification by medical record alone resulted in an underestimate of Hispanic cancer cases and incidence rates. Bias was reduced when medical records and surnames were used together to classify cancer cases as Hispanic. (+info)