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Biomedical subjects

W C Miller

Publications and source records attributed to W C Miller.

At least 19 recordsLinked to original sources
PubMed2006

Tuberculin reactivity in bacille Calmette-Guérin vaccinated populations: a compilation of international data.

SETTING: The effect of previously administered bacille Calmette-Guérin (BCG) vaccine on subsequent tuberculin skin tests (TSTs) complicates screening for latent tuberculosis infection (LTBI) in foreign-born persons. OBJECTIVE: To determine the usefulness of the TST as a screening test for LTBI in foreign-born persons. DESIGN: A literature search was performed of published studies that compared tuberculin reactivity amongst BCG-vaccinated and non-vaccinated groups. The percentages of positive reactors in the two groups were then used to calculate a prevalence ratio. RESULTS: The prevalence ratio varied with the age of the groups tested and the incidence of TB in their countries of origin. The TST performed poorly in vaccinated persons of all ages from countries of low TB incidence, but was a useful screen for LTBI in vaccinated adults from countries of high and intermediate incidence. The test performed poorly as a screening method for vaccinated children under 2 years of age. Its usefulness in vaccinated children aged 2-14 years varied considerably. CONCLUSIONS: The usefulness of the TST as a screening method for LTBI depends on the age of the patient and the incidence of TB in their country of origin.

Age Factors↗
PubMed2005

Monitoring STI prevalence using telephone surveys and mailed urine specimens: a pilot test.

OBJECTIVES: This pilot test assessed the feasibility of a cost effective population based approach to STI monitoring using automated telephone interviews, urine specimen collection kits sent out and returned by US Postal Service mail, and monetary incentives to motivate participation. METHODS: 100 residents of Baltimore, MD, USA, completed an automated telephone survey and agreed to mail in a urine specimen to be tested for chlamydia and gonorrhoea. Participants were paid dollar 10 for completing the survey and dollar 40 for mailing the specimen. RESULTS: 86% of survey participants mailed in a urine specimen for testing. CONCLUSIONS: Automated telephone surveys linked with testing of mailed-in urine specimens may be a feasible lower cost (relative to household surveys) method of estimating infection prevalences in a population.

Adolescent↗
PubMed2005

Measuring energy expenditure using heart rate to assess the effects of wheelchair tyre pressure.

OBJECTIVE: To investigate the effects of wheelchair tyre pressure on mechanics and energy and explore the use of heart rate as a measurement of energy expenditure. DESIGN: A single factor repeated measures design was used. Four tyre pressures (100, 75, 50, 25 psi) represented a change of workload. Each subject wheeled at a constant self-selected wheeling velocity for 8 min. A total of four trials were completed with a 10-min rest between trials. Oxygen consumption, heart rate and distance travelled were collected during each trial. SUBJECTS: Three women and 11 men with spinal cord injury. The mean age for the whole group was 34.5 years. The range of lesion level was T4-L1. RESULTS: There was a significant increase is energy expenditure when tyres were deflated to 50 psi from 100 psi. The mean correlation between heart rate and oxygen consumption was 0.74 for all subjects. For the subjects with lesions above T6 and T6 and below the correlations were 0.55 and 0.82, respectively. CONCLUSIONS: Tyre pressures below 50% inflation add an additional 25% increase in energy expenditure during wheeling. This could be detected using oxygen consumption or heart rate, as heart rate was shown to have a good correlation with oxygen consumption in the spinal cord injured with lesions below T5. Heart rate does have its limitations and it should only be used to measure within-subject differences.

Adult↗
PubMed2004

Growth patterns reflect response to antiretroviral therapy in HIV-positive infants: potential utility in resource-poor settings.

Laboratory monitoring of HIV-infected children is the current standard of care in the United States to guide the appropriate use of antiretroviral therapy (ART). Although ART is becoming a reality in some developing countries, laboratory monitoring of ART is costly, necessitating creative approaches to monitoring. As an initial step to guide monitoring of HIV progression in low resource settings, we assessed the utility of the physical examination to predict clinical progression of HIV. We conducted a retrospective cohort study of HIV-infected children using data from Pediatric AIDS Clinical Trials Group Protocol 300. We developed a clinical predictive model, and compared the utility of the clinical model to the change in HIV RNA viral load as diagnostic tests of ART failure. The clinical model incorporated treatment regimen, age, and height velocity: a three-level clinical predictive model provided likelihood ratios of 0.3, 3.9, and 14. For decline in RNA the likelihood ratios were 0.2 (> 1 log decline), 1.4, and 3.5 (> log increase). We developed a simple clinical predictive model that was able to predict clinical progression of HIV after initiation of new ART. The clinical model performed similarly to using changes in HIV RNA viral load. These data should be validated internationally and prospectively, because the test subjects were from a resource rich environment and growth patterns in undernourished children may be impacted differently by HIV and its treatment. The model was most pertinent to children 36 months of age or younger, and was conducted in children receiving monotherapy and dual therapy.

Anti-HIV Agents↗
PubMed2004

Spatial analysis and mapping of sexually transmitted diseases to optimise intervention and prevention strategies.

OBJECTIVE: We analysed and mapped the distribution of four reportable sexually transmitted diseases, chlamydial infection/non-gonococcal urethritis (chlamydial infection), gonorrhoea, primary and secondary syphilis (syphilis), and HIV infection, for Wake County, North Carolina, to optimise an intervention. METHODS: We used STD surveillance data reported to Wake County, for the year 2000 to analyse and map STD rates. STD rates were mathematically represented as a spatial random field. We analysed spatial variability by calculating and modelling covariance functions of random field theory. Covariances are useful in assessing spatial patterns of disease locally and at a distance. We combined observed STD rates and appropriate covariance models using a geostatistical method called kriging, to predict STD rates and associated prediction errors for a grid covering Wake County. Final disease estimates were interpolated using a spline with tension and mapped to generate a continuous surface of infection. RESULTS: Lower incidence STDs exhibited larger spatial variability and smaller neighbourhoods of influence than higher incidence STDs. Each reported STD had a clustered spatial distribution with one primary core area of infection. Core areas overlapped for all four STDs. CONCLUSIONS: Spatial heterogeneity within STD suggests that STD specific prevention strategies should not be targeted uniformly across Wake County, but rather to core areas. Overlap of core areas among STDs suggests that intervention and prevention strategies can be combined to target multiple STDs effectively. Geostatistical techniques are objective, population level approaches to spatial analysis and mapping that can be used to visualise disease patterns and identify emerging outbreaks.

Adolescent↗
PubMed2004

Measurement properties of the Frenchay Activities Index among individuals with a lower limb amputation.

OBJECTIVE: To assess the reliability and validity of the original and a modified version of the Frenchay Activities Index (FAI) among individuals with a lower limb amputation. DESIGN: Two week test-retest design. SETTING: South Western Ontario Amputee Program, London, Ontario, Canada. SUBJECTS: Consecutive sample of 84 individuals, primarily men (78.6%), mean age 56.5 years with a unilateral transtibial (71.4%) or transfemoral amputation related to traumatic (59.5%) or vascular causes. INTERVENTIONS: All subjects completed a questionnaire containing the FAI and other scales, the 2-minute walk and timed up and go tests during a regularly scheduled clinic visit. Fifty-five subjects completed a second FAI which was mailed to them two weeks later. Twenty-nine others completed the second FAI upon return for testing related to another project. MAIN MEASURES: FAI, Activity-specific Balance Confidence Scale, Prosthetic Evaluation Questionnaire-Mobility Scale, 2-minute walk, timed up and go and walking device aid use. RESULTS: Relative reliability for the FAI (intraclass correlation coefficient (ICC) = 0.79) and FAI-18 (ICC = 0.78) was acceptable, however bias between measurements was detected. Hypothesized relationships (p < 0.001) between both FAI versions and the Activity-specific Balance Confidence Scale, Prosthetic Evaluation Questionnaire-Mobility Scale, 2-minute walk and timed up and go test were observed. Significant group differences were observed for amputation cause, mobility device use, age and years as an amputee. Neither version distinguished between amputee level or gender groups. CONCLUSIONS: The original and modified FAI are valid and reliable tools for unilateral amputees. Reliability is adequate to detect group but not individual level differences. Additional FAI-18 items did not substantially improve the ability to detect between-amputation-group differences.

Activities of Daily Living↗
PubMed2003

LCR testing for gonorrhoea and chlamydia in population surveys and other screenings of low prevalence populations: coping with decreased positive predictive value.

OBJECTIVE: Nucleic acid amplification tests have facilitated field based STD studies and increased screening activities. However, even with highly specific tests, the positive predictive value (PPV) of such tests may be lower than desirable in low prevalence populations. We estimated PPVs for a single LCR test in a population survey in which positive specimens were retested. METHODS: The Baltimore STD and Behavior Survey (BSBS) was a population based behavioural survey of adults which included collecting urine specimens to assess the prevalence of gonorrhoea and chlamydial infection. Gonorrhoea and chlamydial infection were diagnosed by ligase chain reaction (LCR). Nearly all positive results were retested by LCR. Because of cost considerations, negative results were not confirmed. Predicted curves for the PPV were calculated for a single testing assuming an LCR test sensitivity of 95%, and test specificities in the range 95.0%-99.9%, for disease prevalences between 1% and 10%. Positive specimens were retested to derive empirical estimates of the PPV of a positive result on a single LCR test. RESULTS: 579 participants age 18-35 provided urine specimens. 20 (3.5%) subjects initially tested positive for chlamydial infection, and 39 (6.7%) tested positive for gonococcal infection. If positive results on the repeat LCR are taken as confirmation of a "true" infection, the observed PPV for the first LCR testing was 89.5% for chlamydial infection and 83.3% for gonorrhoea. This is within the range of theoretical PPVs calculated from the assumed sensitivities and specificities of the LCR assays. CONCLUSIONS: Empirical performance of a single LCR testing approximated the theoretically predicted PPV in this field study. This result demonstrates the need to take account of the lower PPVs obtained when such tests are used in field studies or clinical screening of low prevalence populations. Repeat testing of specimens, preferably with a different assay (for example, polymerase chain reaction), and disclosure of the non-trivial potential for false positive test results would seem appropriate in all such studies.

Adolescent↗
PubMed2002

Physiological responses to weight-loss intervention in inactive obese African-American and Caucasian women.

BACKGROUND: The physiological responses of inactive obese premenopausal African-American and Caucasian women to the identical exercise training and behavior modification program were compared. METHODS: Inactive obese (96.1+/- 2.9 kg, BMI=34.8 +/- 0.7 kg/m2, % body fat=46.0 +/- 0.8; mean +/- SEM) premenopausal (36 +/- 2 yrs) African-American (n=10) and Caucasian (n=19) women were included. Resting metabolic rate (RMR), respiratory exchange ratio (RER), and maximal aerobic power (VO2max) were measured by indirect calorimetry, and body composition by plethysmography. Resting and maximal heart rates, blood glucose and lipids, and blood pressure were also measured. Treatment consisted of a 13-week diet and exercise behavior modification program. Group mean comparisons were made with a Student's "t"-test or an ANCOVA, which controlled for individual differences in body mass and lean body mass (LBM). Significance was set at p<0.05. RESULTS: Initially, the groups were not significantly different in height, mass, BMI, age, % body fat, fat mass, LBM, girth measurements, RMR, RER, VO2max, blood pressure, or cholesterol profile. The number of weeks completed, number of exercise sessions completed, total minutes of exercise for the entire intervention, average minutes of daily exercise, and total estimated exercise energy expenditure were all similar between groups. Furthermore, both groups reported similar dietary compliance. Both groups reduced body mass, BMI, LBM, girth measurements, and increased VO2max (mlO2 x kg-1 x min-1) significantly and similarly. CONCLUSIONS: African-American and Caucasian women respond the same physiologically to weight loss intervention. The higher prevalence in obesity for African-American women is not due to a different physiological response to diet and exercise.

Adult↗
PubMed2001

Selection for expression of the gonococcal hemoglobin receptor during menses.

All gonococci encode a hemoglobin (Hgb) receptor, but it is phase variable, and most laboratory and clinical isolates are in the Hgb receptor "off" phase. In the present study, we address the question of whether there is a selective advantage to expressing the Hgb receptor during early phases of the menstrual cycle, when Hgb is readily available from menstrual blood. Inclinical isolates collected from women, Hgb use in vitro (Hgb receptor "on" phase) was associated with a shorter time since the onset of the last menstrual cycle, (P=.031, Wilcoxon rank-sum test). Thus, there may be a selective advantage to expression of the gonococcal Hgb receptor during infection of women in the early phases of their menstrual cycles.

Bacterial Proteins↗
PubMed2001

HIV in body fluids during primary HIV infection: implications for pathogenesis, treatment and public health.

OBJECTIVE: To describe initial viral dissemination to peripheral tissues and infectious body fluids during human primary HIV infection. DESIGN: Observational cohort study. METHODS: Blood plasma, cerebrospinal fluid (CSF), seminal plasma, cervicovaginal lavage fluid and/or saliva were sampled from 17 individuals with primary HIV infection (range of time from symptoms onset to sampling, 8--70 days) and one individual with early infection (168 days). Subjects' HIV-1 RNA levels in each fluid were compared with levels from antiretroviral-naive controls with established HIV infection. For study subjects, correlations were assessed between HIV-1 RNA levels and time from symptoms onset. Responses to antiretroviral therapy with didanosine + stavudine + nevirapine +/- hydroxyurea were assessed in each compartment. RESULTS: HIV-1 RNA levels were highest closest to symptoms onset in blood plasma (18 patients) and saliva (11 patients). CSF HIV-1 RNA levels (five patients) appeared lower closer to symptoms onset, although they were higher overall in primary versus established infection. Shedding into seminal plasma (eight patients) and cervicovaginal fluid (two patients) was established at levels observed in chronic infection within 3--5 weeks of symptoms onset. High-level seminal plasma shedding was associated with coinfection with other sexually transmitted pathogens. Virus replication was suppressed in all compartments by antiretroviral therapy. CONCLUSIONS: Peak level HIV replication is established in blood, oropharyngeal tissues and genital tract, but potentially not in CSF, by the time patients are commonly diagnosed with primary HIV infection. Antiretroviral therapy is unlikely to limit initial virus spread to most tissue compartments, but may control genital tract shedding and central nervous system expansion in primary infection.

Anti-HIV Agents↗
PubMed2001

Evaluation of the BOD POD for estimating percentage body fat in a heterogeneous group of adult humans.

The primary purpose of this investigation was to compare estimations of percentage body fat (%fat) using air displacement plethysmography (ADP) and hydrostatic weighing (HW) in a heterogeneous (age and %fat) sample of the population. Of secondary importance was to determine whether there were differences between the two methods among lean (n = 32), average (n = 34) and overweight (n = 29) subsets of this sample. A total of 95 adults (men 27, women 68) ranging in age from 18-52 years volunteered for this study. Test-retest reliability for %fat ADP (n = 16) was 0.99 with a technical error of 0.75%fat and a coefficient of variation of 3.4%fat. Mean body density using ADP [1.048 (SD 0.016) g.ml-1] was not significantly different when compared to HW [1.049 (SD 0.017) g.ml-1], which corresponded to a non-significant difference in %fat [22.5 (SD 7.3)% ADP compared to 22.0 (SD 7.6)% HW]. Regression analysis provided the equation: %fat HW = 0.9121%fat ADP + 1.5123; r = 0.88, SEE = 3.6, which did not differ significantly from the line of identity. Data for the subsets revealed a significant overestimation of %fat ADP [16.4 (SD 4.8)%] compared to HW [14.1 (SD 3.2)%] (P = 0.001) for lean individuals while no difference was found in the average [21.9 (SD 4.4)%fat ADP compared to 22.0 (SD 3.4)%fat HW] or overweight [29.9 (SD 5.5)%fat ADP compared to 30.8 (SD 4.1)%fat HW] subsets. Measuring %fat by ADP is a highly reliable method and valid when compared to HW for a heterogeneous sample of adults. The ADP method requires little expertise to operate, is quick to perform, and may be more accommodating for certain individuals compared to HW. However, in this study ADP was less valid for lean individuals. Further investigation is warranted to determine the bias of this method for subsets of the population which may be outside the average range of %fat (men 15.4%-22.0%, women 18.4%-28.5%).

Adipose Tissue↗
PubMed2001

The health at any size paradigm for obesity treatment: the scientific evidence.

Traditional weight loss (TWL) treatments have been unsuccessful at reducing the prevalence of obesity in the population. Health-care professionals and consumers have criticized TWL treatments as being detrimental to the obese person's health. Consequently, an alternative approach to obesity treatment, the health at any size (H@AS) paradigm, has been proposed. The H@AS paradigm is based on the philosophy that once diet restrictions and barriers to activity have been removed, the individual will develop healthier eating and activity patterns that lead to a naturally healthy body weight. This paper reviews the philosophical foundation and the scientific data that support and oppose the H@AS paradigm and compares it with that of TWL treatments.

Diet↗
PubMed2001

The prevalence and risk factors of falling and fear of falling among lower extremity amputees.

OBJECTIVE: To estimate the falling experience and fear of falling status and to describe characteristics associated with falling and fear of falling. DESIGN: Population-based consecutive sample survey and chart review. SETTING: Two Canadian, regional, university-affiliated outpatient amputee clinics. PARTICIPANTS: The sample (n = 435; mean age, 62 +/- 15.7 yr) of community-living participants was mostly male (71%), had unilateral (below knee 73%; above knee 27%) amputations primarily for vascular (53% vs 47% nonvascular) reasons. INTERVENTION: Review patient charts and survey questionnaires to determine sociodemographic information (eg, social support), information about the amputation (eg, cause, level, problems), physical health and function (eg, pain, limitations, comorbidity), and psychologic state (depression, adaptation). MAIN OUTCOME MEASURES: Occurrence of a fall in the past 12 months and presence of a fear of falling. RESULTS: Exactly 52.4% subjects reported falling in the past year, whereas 49.2% reported a fear of falling. Logistic regression analyses revealed falling was related to having an above knee amputation (odds ratio [OR] = 2.78; 95% confidence interval [CI] = 1.71-4.51), back (OR = 1.96; 95% CI = 1.08-3.54) and joint (OR = 1.67; 95% CI = 1.01-2.74) pain, and multiple stump and prosthesis problems (OR = 3.09; 95% CI = 1.58-6.04). Having had the amputation > or = 4 years in the past was protective (OR =.53; 95% CI =.29-.89). Factors related to an increase risk of fear of falling included having to concentrate on each step while walking (OR = 4.06; 95% CI = 2.46-6.71) and having a fall in the past 12 months (OR = 1.62; 95% CI = 1.04-2.54), whereas being male (OR = 0.35; 95% CI =.21-.57) and having good to excellent perceived health (OR =.35; 95% CI =.21-.58) were protective. CONCLUSIONS: Falling and fear of falling are pervasive among amputees. Comprehensive and ongoing intervention and education should be considered. Research is required to assess the consequences of falling and fear of falling.

Accidental Falls↗
PubMed2001

The influence of falling, fear of falling, and balance confidence on prosthetic mobility and social activity among individuals with a lower extremity amputation.

OBJECTIVE: To assess in amputee patients the relationship between having fallen in the past 12 months, fear of falling, and balance confidence on mobility capability, mobility performance, and social activity. DESIGN: Population-based survey and chart review. SETTING: Two university-affiliated outpatient amputee programs in southwestern Ontario. PARTICIPANTS: Community-living individuals (n = 435) with a unilateral lower limb amputation. INTERVENTIONS: Patient chart review and a survey questionnaire. MAIN OUTCOME MEASURES: Self-report assessment of prosthetic capability and performance and social activity participation was assessed with the Prosthetic Evaluation Questionnaire mobility subscale, the Houghton Scale, and the Frenchay Activities Index. RESULTS: Falling experiences in the past 12 months were not significantly associated with any outcomes. Fear of falling was important in univariate relationships in all 3 outcomes, but not when balance confidence was included in multivariable modeling. Balance confidence was statistically significant with each of the outcomes and remained significant with inclusion of the covariates. There was statistical interaction (balance confidence x automatism; balance confidence x medication count) in modeling mobility capability and in modeling mobility performance (balance confidence x pain + balance confidence x amputation level). The final models accounted for 70%, 60%, and 55% of the variation in mobility capability, mobility performance, and social activity, respectively. CONCLUSION: Balance confidence was the only factor associated with mobility capability and performance and social activity in the final adjusted models. Clinicians and researchers should consider this variable in the rehabilitation of amputee patients.

Accidental Falls↗
PubMed2001

Lower extremity prosthetic mobility: a comparison of 3 self-report scales.

OBJECTIVE: To assess and compare the reliability and validity of the Houghton Scale, the Prosthetic Profile of the Amputee Locomotor Capabilities Index (PPA-LCI), and the Prosthetic Evaluation Questionnaire (PEQ) mobility subscale, 3 disease-specific self-report measures of functional mobility for lower extremity prosthetic mobility. DESIGN: Four-week test-retest: 1 sample for reliability analyses, 1 sample for validity analyses. SETTING: University-affiliated outpatient amputee clinic, in Ontario, Canada. PARTICIPANTS: Two outpatient amputee samples (sample 1 [n = 55], for reliability analysis; sample 2 [n = 329], for validity analysis). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Test-retest of reliability and convergent validity of the 3 scales. Convergent validity and discriminative ability were also assessed after setting a priori hypotheses for 2 scales of walking performance, balance confidence, and other indicators of ambulatory ability. RESULTS: The reliability of the PPA-LCI (intraclass correlation coefficient [ICC] = .88) was slightly higher than the Houghton Scale (ICC = .85) and the PEQ mobility subscale (ICC = .77). The PPA-LCI was prone to high ceiling effects (40%) that would limit its ability to detect improvement. Evidence for convergent validity, when compared with the 2-Minute Walk Test, Timed Up and Go, and the Activity-Specific Balance Confidence Scale, was supported as hypothesized in all the scales. Each of the scales was able to discriminate between different groups for amputation cause, walking distance, mobility device use, and automatism, with each having varying strength related to relative precision. The Houghton Scale was the only scale able to distinguish between amputation levels. CONCLUSIONS: Reliability and validity of all the scales are acceptable for group level comparison. None of the scales had clearly superior psychometric properties compared with the others. Further research is required to assess responsiveness.

Artificial Limbs↗