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Stephen Shiboski

Publications and source records attributed to Stephen Shiboski.

14 recordsLinked to original sources
PubMed2006

Audio computer-assisted self-interviewing in reproductive health research: reliability assessment among women in Harare, Zimbabwe.

PURPOSE: Research on the measurement of HIV risk demonstrates that interview mode can affect reporting; however, few studies have applied these findings to assessments of hormonal contraceptive use. This paper examines how audio computer-assisted self-interviewing (ACASI) influenced reports of hormonal contraceptive use and pregnancy among Zimbabwean women. METHODS: Using a prospective, randomized, cross-over design, we compared self-reports obtained with ACASI and face-to-face (FTF) interview among 655 women enrolled in a prospective study on hormonal contraceptive use and HIV acquisition. In addition, self-report data were compared to those collected during clinical exams. RESULTS: Compared to FTF interviews, reports of hormonal contraceptive use were lower in ACASI [odds ratio (OR)=0.6; 95% confidence interval (95% CI)=0.5-0.6], and reports of pregnancy were higher (OR=1.5; 95% CI=1.1-1.9). Both modes of self-report differed from records on contraceptive method disbursement. CONCLUSION: Although ACASI yielded higher reports of several reproductive health behaviors, discrepancies between self-reports and clinical data on method disbursement highlight persistent measurement challenges.

Adult↗
PubMed2006

Covariates of cervical cytokine mRNA expression by real-time PCR in adolescents and young women: effects of Chlamydia trachomatis infection, hormonal contraception, and smoking.

Measurements of mucosal immune parameters in the uterine cervix are potentially influenced by numerous factors, including infections, endogenous and exogenous hormones, semen, and nicotine and its metabolites in cervical mucus. The objective of this study was to examine correlates of immunoregulatory cytokine mRNA expression in cervical cytology samples in a cross-sectional design. Samples, collected at study entry by cervical cytology brush from 368 women aged 13-21 enrolled in a longitudinal study of the natural history of human papillomavirus (HPV) infection, were tested by quantitative RT-PCR for expression of IFN-gamma, IL-4, IL-10, and IL-12. In a multivariate analysis, elevated levels of IFN-gamma, IL-10, and IL-12 were significantly (p < 0.05) associated with several variables, including current C. trachomatis infection, recent intercourse, and current oral contraceptive pill use. Suppressed IL-4 and IL-10 levels were associated with cigarette smoking within the last 24 h. Time since last menstrual period did not affect any of the cytokines; in a substudy of weekly cytokine variability, however, IL-10 showed a non-significant trend toward higher levels around the time of menstruation.

Adolescent↗
PubMed2006

Phenotypic predictors of response to simvastatin therapy among African-Americans and Caucasians: the Cholesterol and Pharmacogenetics (CAP) Study.

Although statins are effective lipid-lowering agents, the phenotypic and demographic predictors of such lowering have been less well examined. We enrolled 944 African-American and white men and women who completed an open-label, 6-week pharmacogenetics trial of 40 mg of simvastatin. The phenotypic and demographic variables were examined as predictors of the change in lipids and lipoproteins using linear regression analysis. On average, treatment with simvastatin lowered low-density lipoprotein (LDL) cholesterol by 54 mg/dl and increased high-density lipoprotein (HDL) cholesterol by 2 mg/dl. Compared with African-Americans, whites had a 3-mg/dl greater LDL reduction and a 1-mg/dl higher HDL elevation, independent of other variables, including baseline lipoprotein levels (p <0.01). Multivariate analyses revealed moderate subgroup differences, with older participants having a larger decrease in LDL cholesterol and apolipoprotein B levels compared with younger participants (p <0.001), women having larger increases in HDL than men (p <0.01), nonsmokers having larger decreases in LDL and triglyceride levels compared with smokers (p <0.05), those with hypertension having smaller decreases in apolipoprotein B than those without hypertension (p <0.05), and those with a larger waist circumference having a diminished lowering of triglycerides in response to treatment with simvastatin (p <0.01). In conclusion, treatment with simvastatin produced favorable lipid and lipoprotein changes among all participants. The magnitude of the lipid and lipoprotein responses, however, differed among participants according to a number of phenotypic and demographic characteristics.

Adult↗
PubMed2006

Sexual bridging socially and over time: a simulation model exploring the relative effects of mixing and concurrency on viral sexually transmitted infection transmission.

BACKGROUND: Sexual partnerships between people at higher and lower risk for sexually transmitted infections (STIs) (i.e., bridging) occur through dissortative mixing and concurrent partnerships, yet the relative effects of these network patterns on population STI spread are poorly understood. GOAL: Using a stochastic model, the authors investigated the impact of mixing and concurrency on the spread of a persistent viral STI. STUDY DESIGN: A total of 1,050 populations were simulated of 1,000 subjects over 400 weeks with varied concurrency levels and mixing patterns. STI prevalence and the average number of secondary transmissions per subject were analyzed with regression. RESULTS: Mixing had a greater impact on prevalence for all groups, whereas concurrency was significant for only the lowest activity group. Mixing patterns moderated the magnitude of concurrency's impact on secondary transmissions. CONCLUSIONS: Through connecting subgroups of differential risk, sexual mixing facilitates dissemination of STIs throughout a population. Concurrency expedites transmission by shortening the time between sexual contacts among infected and susceptible persons, particularly during the highly infectious period.

Computer Simulation↗
PubMed2005

Evaluating change in health-related quality of life in adult rhinitis: responsiveness of the Rhinosinusitis Disability Index.

BACKGROUND: The Rhinosinusitis Disability Index (RSDI) is a validated measure of health-related quality of life (HRQL) in rhinitis. Responsiveness of the RSDI to changes in health status over time has not been described. METHODS: We studied adults with a self-reported physician diagnosis of rhinitis identified through a national telephone survey. HRQL was assessed at baseline and at 24 months using the RSDI. Symptom severity, physical health status (SF-12 PCS), psychological mood (CES-D), and perceived control of symptoms were also assessed at the time of each interview. In addition, we ascertained specific health outcomes attributed to rhinitis, including days of restricted activity, job effectiveness, number of physician visits, and medication costs. RESULTS: Of 109 subjects interviewed at baseline, 69 (63%) were re-interviewed 24 months later. RSDI scores improved by = 0.5 standardized response mean in 13 (19%) subjects and worsened in 17 (25%). Change in the RSDI over time correlated with changes in symptom severity (r = 0.38, p = 0.001), physical health (r = -0.39, p = 0.001), mood (r = 0.37, p = 0.002) and perceived control of symptoms (r = -0.37, p = 0.01). In multivariate analyses adjusted for baseline health status, improvement in RSDI was associated with less restricted activity (p = 0.01), increased job effectiveness (p = 0.03), and decreased medication costs (p = 0.05), but was not associated with change in the number of physician visits from baseline (p = 0.45). CONCLUSION: The RSDI is responsive to changes in health status and predicts rhinitis-specific health outcomes.

Adolescent↗
PubMed2005

Impact of exogenous glucocorticoid use on salivary cortisol measurements among adults with asthma and rhinitis.

The diurnal rhythm of cortisol secretion in chronic disease can reflect the interactions between exogenous and endogenous factors. Exogenous glucocorticoid use may impact salivary cortisol measurements, but this has not been well-studied in ambulatory settings. In this report salivary cortisol levels were used to evaluate aspects of the diurnal rhythm of cortisol secretion within an ambulatory population of patients with asthma and allergic rhinitis. 183 persons with asthma with or without concomitant rhinitis and 34 persons with rhinitis alone were asked to collect at home, two saliva samples, 30 min after awakening and 12h later. The salivary cortisol levels were quantified by enzyme immunoassay. The recent use of glucocorticoids in the study group was determined by interview and direct examination of medications. We report that the median salivary cortisol levels 30 min post-awakening significantly differed by exogenous steroid status: no glucocorticoid use (n = 91), 10.1 nmol/l; nasal gluco-corticoid use alone (n = 25), 11.4 nmol/l; inhaled glucocorticoids (with or without concomitant nasal glucocorticoids; n = 76), 9.0 nmol/l; systemic glucocorticoids (n = 17), 4.0 nmol/l; (P = 0.02). 12-h post-awakening salivary cortisol values among the groups were similar (P = 0.85). The median 30-min post-awakening cortisol differed significantly by type and amount of inhaled steroid used: non-fluticasone users (n = 21), 11.5 nmol/l; lower dose fluticasone (<800 microg per day, n = 35); 9.2 nmol/l; and higher dose fluticasone (> or =800 microg, n=20), 5 nmol/l; (P=0.01). We conclude that in an ambulatory setting, exogenous glucocorticoid use can decrease the 30 min post-awakening but not the 12-h post-awakening salivary cortisol levels, an effect that should be taken into account in assessing the effects of other potential determinants on cortisol secretion.

Administration, Inhalation↗
PubMed2005

Risk factors for estrogen receptor-positive breast cancer.

HYPOTHESIS: Some risk factors associated with breast cancer may be more predictive of estrogen receptor (ER)- positive than ER-negative tumors. DESIGN: Survey of patients enrolled in a study of breast cancer risk factors. SETTING: Community population in a northern California county. PATIENTS: A total of 234 individuals diagnosed as having breast cancer between July 1, 1997, and June 30, 1999, reporting Marin County, California, residence and participating in a questionnaire regarding exposure to breast cancer risk factors. MAIN OUTCOME MEASURE: Diagnosis of ER-positive vs ER-negative breast cancer. RESULTS: Comparison between ER-positive and ER-negative cases showed several factors predictive of ER-positive tumors. In a multivariate model, years of hormone therapy use remained the most significant predictor of ER-positive disease. CONCLUSIONS: Patients diagnosed as having ER-positive breast cancer were more likely to have undergone hormone therapy. The excess of ER-positive breast cancers reported in Marin County could, therefore, in part, be related to hormone therapy.

Breast Neoplasms↗
PubMed2004

Human immunodeficiency virus type 2 DNA vaccine provides partial protection from acute baboon infection.

We determined if the genetic adjuvants, granulocyte-macrophage colony stimulating factor (GM-CSF) and B7-2, could improve the immunogenicity and efficacy of an HIV-2 DNA vaccine. The vaccine consisted of the HIV-2 tat, nef, gag, and env genes synthesized using optimized codons and formulated with cationic liposomes. Baboons (Papio cynocephalus hamadryas) were immunized by the intramuscular, intradermal, and intranasal routes with these expression constructs and challenged with HIV-2(UC2) by the intravaginal route. In the first month after HIV-2 vaginal challenge, the baboons receiving the HIV-2 DNA vaccine with or without the genetic adjuvants had significant reductions in the viral loads in the peripheral blood mononuclear cells (PBMC) (P = 0.028) while the reductions in their plasma viremia were suggestive of a protective effect (P = 0.1). These data demonstrate that partial protection against HIV-2 vaginal challenge, as measured by reduced viral load, can be achieved using only a DNA vaccine formulation.

Adjuvants, Immunologic↗
PubMed2003

Applications of continuous time hidden Markov models to the study of misclassified disease outcomes.

Disease progression in prospective clinical and epidemiological studies is often conceptualized in terms of transitions between disease states. Analysis of data from such studies can be complicated by a number of factors, including the presence of individuals in various prevalent disease states and with unknown prior disease history, interval censored observations of state transitions and misclassified measurements of disease states. We present an approach where the disease states are modelled as the hidden states of a continuous time hidden Markov model using the imperfect measurements of the disease state as observations. Covariate effects on transitions between disease states are incorporated using a generalized regression framework. Parameter estimation and inference are based on maximum likelihood methods and rely on an EM algorithm. In addition, techniques for model assessment are proposed. Applications to two binary disease outcomes are presented: the oral lesion hairy leukoplakia in a cohort of HIV infected men and cervical human papillomavirus (HPV) infection in a cohort of young women. Estimated transition rates and misclassification probabilities for the hairy leukoplakia data agree well with clinical observations on the persistence and diagnosis of this lesion, lending credibility to the interpretation of hidden states as representing the actual disease states. By contrast, interpretation of the results for the HPV data are more problematic, illustrating that successful application of the hidden Markov model may be highly dependent on the degree to which the assumptions of the model are satisfied.

Adolescent↗
PubMed2003

A comprehensive study of the direct and indirect costs of adult asthma.

BACKGROUND: Asthma is a common and costly health condition, but most estimates of its economic effect have relied on secondary sources with limited condition-specific detail. OBJECTIVE: We sought to estimate the magnitude of direct and indirect costs of adult asthma from the perspective of society. METHODS: We used cross-sectional survey data from an ongoing community-based panel study of 401 adults with asthma originally derived from random samples of northern California pulmonologists, allergist-immunologists, and family practitioners to assess health care use for asthma, to assess purchase of items to assist with asthma care, and to measure work and other productivity losses. Unit costs derived from public-use and proprietary data sources were then assigned to the survey items. RESULTS: Total per-person annual costs of asthma averaged $4912 US dollars, with direct and indirect costs accounting for $3180 US dollars (65%) and $1732 US dollars (35%), respectively. The largest components within direct costs were pharmaceuticals ($1605 US dollars [50%]), hospital admissions ($463 US dollars[15%]), and non-emergency department ambulatory visits ($342 US dollars [11%]). Within indirect costs, total cessation of work accounted for $1062 US dollars (61%), and the loss of entire work days among those remaining employed accounted for another $486 US dollars (28%). Total per-person costs were $2646, $4530, and $12,813 US dollars for persons self-reporting mild, moderate, and severe asthma, respectively (P <.0001, 1-way ANOVA). CONCLUSION: Asthma-related costs are substantial and are driven largely by pharmaceuticals and work loss.

Absenteeism↗
PubMed2002

Relationship of CD8(+) T cell noncytotoxic anti-HIV response to CD4(+) T cell number in untreated asymptomatic HIV-infected individuals.

During chronic HIV infection, asymptomatic individuals demonstrate a strong CD8(+) cell noncytotoxic antiviral response (CNAR). With the onset of symptoms or reduction in CD4(+) cell counts, CNAR decreases. Presently, it is recommended that infected individuals receive antiretroviral therapy if CD4(+) cell counts fall below 350 cells/microL. To determine whether CNAR lends support to this recommendation for initiation of antiretroviral treatment, we examined CNAR in 20 healthy, untreated, HIV-infected men exhibiting a range of CD4(+) cell numbers. Our results indicate that the asymptomatic untreated HIV-infected individuals with less than 300 CD4(+) cells/microL had a significantly lower CNAR than those with higher CD4(+) cell counts. These data on CNAR in untreated, healthy, HIV-infected individuals support the current recommendation for when to initiate antiretroviral therapy.

Adult↗
PubMed2002

Incidence of acute urinary tract infection in young women and use of male condoms with and without nonoxynol-9 spermicides.

BACKGROUND: Acute urinary tract infection is one of the most common infections seen in primary care. METHODS: We conducted a nested case-control study among a cohort of 519 women, ages 15-29 years, enrolled in a contraceptive acceptability study to examine whether recent use of male condoms increases urinary tract infection risk. RESULTS: One hundred sixty-five incident urinary tract infections were identified during 12-month follow-up periods in a cohort study that was conducted between 1996 and 1999. After exclusions for urinary tract infection recurrences, pregnancy, antibiotic use, diabetes, diaphragm/cervical cap use, or urinary tract abnormalities, there were 100 cases and 200 controls. Compared with women not using barrier methods (and after adjustment for age, urinary tract infection history, hormonal method use, and frequency of sex) the odds ratio (OR) for any reported use of condoms coated with spermicide (Nonoxynol-9) in the previous 30 days was 2.8 (95% [confidence interval] CI = 1.2-6.5). The OR was 11.5 (95% CI = 2.5-53) for exclusive Nonoxynol-9-coated condom use. The OR for exclusive use of non-Nonoxynol-9-coated condoms was 7.4 (95% CI = 1.6-35). CONCLUSIONS: In this study, use of male condoms was associated with increased urinary tract infection risk; the largest risk was associated with exclusive condom use and use of Nonoxynol-9-coated condoms.

Acute Disease↗
PubMedDate not supplied

Regression of low-grade squamous intra-epithelial lesions in young women.

BACKGROUND: The aim of this study was to assess the probability of low-grade squamous intra-epithelial lesion (LSIL) regression in young women, and to examine the factors associated with this regression. METHODS: In a longitudinal study of human papilloma virus (HPV) infection, female adolescents aged 13-22 years were examined every 4 months by cytology, colposcopy, and HPV DNA status. Both prevalent and incident LSIL cases were included in the analysis, with regression defined as at least three consecutive normal Pap smears. FINDINGS: Median follow-up time from baseline (defined as the time of first LSIL diagnosis) for the 187 women with LSIL was 61 months (IQR 34-80). Median time they had been sexually active at diagnosis was 3.2 years (2.6-6.5). Probability of regression for the entire cohort was 61% (95% CI 53-70) at 12 months and 91% (84-99) at 36 months of follow-up. No associations were found between LSIL regression and HPV status at baseline, sexual behaviour, contraceptive use, substance or cigarette use, incident sexually transmitted infection, or biopsy. Multivariate analysis showed that only HPV status at the current visit was associated with rate of regression, whether infection was caused by one or more viral types (relative hazard=0.3 [95% CI 0.21-0.42], and 0.14 [0.08-0.25], respectively). INTERPRETATION: The high rate of regression recorded in this study lends support to observation by cytology in the management of LSIL in female adolescents. Negative HPV status was associated with regression, suggesting that HPV testing could be helpful in monitoring LSIL.

Adolescent↗