Quantitative Bias Analysis of misclassification in case-control studies: an example with Human Papillomavirus and Oropharyngeal Cancer.

OBJECTIVE: Laprise et al. (2019) observed a positive association between oral sex practices and oropharyngeal cancers (OPC) among HPV-negative individuals. Because oral HPV infections are likely to be transmitted through oral sex, these results are counterintuitive. We revisit Laprise et. al's analysis with the objective of estimating the impact of misclassification of HPV infection on the association between oral sex practices and OPC. METHODS: Data were drawn from the Head and Neck Cancer (HeNCe) Life study, a hospital-based case control study of head and neck cancer with frequency-matched controls by age and sex from 4 major referral hospitals in Montreal, Canada. We included only OPC cases (n = 188) and controls (n = 429) and used predictive value weighting, under differential and non-differential scenarios, to evaluate the misclassification. Subsequently, we used logistic regression and 95% confidence intervals to estimate the association between oral sex practice and OPC among HPV-negative individuals. RESULTS: Our results showed that the previously reported association between oral sex practices and OPC among HPV-negative individuals was attenuated or nullified both under differential and non-differential scenarios. CONCLUSION: The association between oral sex practice and OPC could be explained by biases in the data (e.g., HPV mediator misclassification). Our results highlight the need for widespread adoption of Quantitative Bias Analysis in oral health research.

Cost-effectiveness of active case-finding of household contacts of pulmonary tuberculosis patients in a low HIV, tuberculosis-endemic urban area of Lima, Peru.

We compared the cost-effectiveness (CE) of an active case-finding (ACF) programme for household contacts of tuberculosis (TB) cases enrolled in first-line treatment to routine passive case-finding (PCF) within an established national TB programme in Peru. Decision analysis was used to model detection of TB in household contacts through: (1) self-report of symptomatic cases for evaluation (PCF), (2) a provider-initiated ACF programme, (3) addition of an Xpert MTB/RIF diagnostic test for a single sputum sample from household contacts, and (4) all strategies combined. CE was calculated as the incremental cost-effectiveness ratio (ICER) in terms of US dollars per disability-adjusted life years (DALYs) averted. Compared to PCF alone, ACF for household contacts resulted in an ICER of $2155 per DALY averted. The addition of the Xpert MTB/RIF diagnostic test resulted in an ICER of $3275 per DALY averted within a PCF programme and $3399 per DALY averted when an ACF programme was included. Provider-initiated ACF of household contacts in an urban setting of Lima, Peru can be highly cost-effective, even including costs to seek out contacts and perform an Xpert/MTB RIF test. ACF including Xpert MTB/RIF was not cost-effective if TB cases detected had high rates of default from treatment or poor outcomes.

Cervical dilation at time of caesarean delivery in nulliparous women: a population-based cohort study.

OBJECTIVES: Our objective was to describe contemporary practice patterns in the timing of caesarean delivery in relation to cervical dilation, overall and by indication for caesarean. Our secondary objective was to examine how commonly caesarean delivery was performed for labour dystocia at dilations below 4 cm or without the use of oxytocin, overall and between hospitals. DESIGN: Retrospective, population-based cohort study. SETTING: Ontario, Alberta, and British Columbia, Canada, 2008-2012. POPULATION: Nulliparous women in labour who delivered term singletons in cephalic position. METHODS: Histograms were used to examine the distribution of cervical dilation at time of caesarean delivery, overall and by indication for caesarean. Funnel plots were used to illustrate variation in hospital-level rates of caesarean deliveries for labour dystocia that were performed early (<4 cm dilation) or without the use of oxytocin. MAIN OUTCOME MEASURES: Cervical dilation (in centimetres) at time of caesarean delivery. RESULTS: The population-based cohort comprised 392 025 women, of whom 18.8% had a caesarean delivery. Of first-stage caesareans for labour dystocia in women who entered labour spontaneously, 13.6% (95% CI 12.9, 14.2) had dilations <4 cm [hospital-level inter-quartile range (IQR): 6.2% to 20.0%] and 29.5% (95% CI 28.6, 30.4) did not receive oxytocin to treat their dystocia (hospital-level IQR: 22.1-54.6%). CONCLUSIONS: The proportion of caesareans done before 4 cm dilation or without oxytocin varies substantially across hospitals and suggests the need for institutions to review their practices and ensure that management of labour practice guidelines are followed. TWEETABLE ABSTRACT: Many caesareans for labour dystocia are performed early during labour (<4 cm dilation) or without oxytocin.

Place and health in diabetes: the neighbourhood environment and risk of depression in adults with type 2 diabetes.

BACKGROUND: Depression is a common co-illness in people with diabetes. Evidence suggests that the neighbourhood environment impacts the risk of depression, but few studies have investigated this effect in those with diabetes. We examined the effect of a range of neighbourhood characteristics on depression in people with Type 2 diabetes. METHODS: This cohort study used five waves of data from 1298 participants with Type 2 diabetes from the Diabetes Health Study (2008-2013). We assessed depression using the Patient Health Questionnaire. We measured neighbourhood deprivation using census data; density of services using geospatial data; level of greenness using satellite imagery; and perceived neighbourhood characteristics using survey data. The effect of neighbourhood factors on risk of depression was estimated using survival analysis, adjusting for sociodemographic variables. We tested effect modification by age, sex and socio-economic characteristics using interaction terms. RESULTS: More physical activity facilities, cultural services and a greater level of greenness in the neighbourhood were associated with a lower risk of depression in our sample, even after adjusting for confounders. Material deprivation was associated with increased risk of depression, particularly in participants who were older or retired. CONCLUSIONS: Characteristics of neighbourhoods were associated with the risk of depression in people with Type 2 diabetes and there were vulnerable subgroups within this association. Clinicians are encouraged to consider the neighbourhood environment of their patients when assessing the risk of depression. Future intervention research is need for health policy recommendations.

Fetal death and preterm birth associated with maternal influenza vaccination: systematic review.

BACKGROUND: Before 2012, few studies had addressed pregnancy outcomes following maternal influenza vaccination; however, the number of publications on this topic has increased recently. OBJECTIVES: To review comparative studies evaluating fetal death or preterm birth associated with influenza vaccination during pregnancy. SEARCH STRATEGY: We searched bibliographic databases from inception to April 2014. SELECTION CRITERIA: Experimental or observational studies assessing the relationship between influenza vaccination during pregnancy and fetal death or preterm birth. DATA COLLECTION AND ANALYSIS: Two reviewers independently abstracted data from studies meeting the inclusion criteria. MAIN RESULTS: We included one randomised clinical trial and 26 observational studies. Meta-analyses were not considered appropriate because of high clinical and statistical heterogeneity. Three studies of fetal death at any gestational age reported adjusted effect estimates in the range 0.56-0.79, and four of five studies of fetal death at <20 weeks reported adjusted estimates between 0.89 and 1.23, all with confidence intervals including 1.0. Adjusted effect estimates for four of five studies of fetal death at ≥20 weeks ranged from 0.44 to 0.77 (two with confidence intervals not crossing 1.0), whereas a fifth reported a non-significant effect in the opposite direction. Among 19 studies of preterm birth, there was no strong evidence suggesting any increased risk, and meta-regression did not explain the moderate between-study heterogeneity (I(2) = 57%). AUTHORS' CONCLUSIONS: Most studies reported no association between fetal death or preterm birth and influenza vaccination during pregnancy. Although several reported risk reductions, results may be biased by methodological shortcomings of observational studies of influenza vaccine effectiveness.

Ethnicity and gestational diabetes in New York City, 1995-2003.

OBJECTIVE: To characterise the patterns of occurrence of gestational diabetes among a wide range of ethnic groups that reside in New York City. DESIGN: Birth records and hospital discharge data were linked to more accurately assess the risk of gestational diabetes by ethnicity, compare risk in US-born to foreign-born women, and assess time trends. SETTING: New York City. POPULATION: All singleton live births occurring between 1995 and 2003. METHODS: Multivariable binomial regression analysis of ethnicity and gestational diabetes, yielding adjusted risk ratios with non-Hispanic white women as the referent. MAIN OUTCOME MEASURE: Diagnosis of gestational diabetes on birth certificate or in hospital discharge. RESULTS: Adjusted relative risks (aRRs) were modestly elevated for African-Americans and sub-Saharan Africans and somewhat higher (<2.0) for non-Hispanic Caribbeans, Hispanic Caribbeans, Central Americans, and South Americans. The aRR was 4.7 (95% CI = 4.6-4.9) for South Central Asians (with an absolute gestational diabetes risk of 14.3%), 2.8 (95% CI = 2.7-3.0) among South-East Asian and Pacific Islanders, and 2.3 (95% CI = 2.2-2.4) among East Asians. Among South Central Asians, the greatest risks were found for women from Bangladesh (aRR = 7.1, 95% CI = 6.8-7.3). Foreign-born women consistently had higher risk than US-born women. Risk for gestational diabetes increased over time among South Central Asians, some Hispanic groups, and African-Americans. CONCLUSIONS: Risk of gestational diabetes appears to vary markedly among ethnic groups, subject to potential artefacts associated with screening and diagnosis. These differences would have direct implications for health care and may suggest aetiologic hypotheses.

Inequalities in Indigenous Oral Health: Findings from Australia, New Zealand, and Canada

The objective was to compare absolute differences in the prevalence of Indigenous-related inequalities in dental disease experience and self-rated oral health in Australia, Canada, and New Zealand. Data were sourced from national oral health surveys in Australia (2004 to 2006), Canada (2007 to 2009), and New Zealand (2009). Participants were aged ≥18 y. The authors measured age- and sex-adjusted inequalities by estimating absolute prevalence differences and their corresponding 95% confidence intervals (95% CIs). Clinical measures included the prevalence of untreated decayed teeth, missing teeth, and filled teeth; self-reported measures included the prevalence of "fair" or "poor" self-rated oral health. The overall pattern of Indigenous disadvantage was similar across all countries. The summary estimates for the adjusted prevalence differences were as follows: 16.5 (95% CI: 11.1 to 21.9) for decayed teeth (all countries combined), 18.2 (95% CI: 12.5 to 24.0) for missing teeth, 0.8 (95% CI: -1.9 to 3.5) for filled teeth, and 17.5 (95% CI: 11.3 to 23.6) for fair/poor self-rated oral health. The I2 estimates were small for each outcome: 0.0% for decayed, missing, and filled teeth and 11.6% for fair/poor self-rated oral health. Irrespective of country, when compared with their non-Indigenous counterparts, Indigenous persons had more untreated dental caries and missing teeth, fewer teeth that had been restored (with the exception of Canada), and a higher proportion reporting fair/poor self-rated oral health. There were no discernible differences among the 3 countries.

Mortality from coronary heart disease and cardiovascular disease among adult U.S. Hispanics: findings from the National Health Interview Survey (1986 to 1994).

OBJECTIVES: We sought to estimate the coronary heart disease (CHD) and cardiovascular disease (CVD) mortality experience of U.S. Hispanics. BACKGROUND: Limited information is available concerning the mortality from CHD among U.S. Hispanics, the nation's second largest minority group. METHODS: The study used data from the National Health Interview Survey (1986 to 1994), including representative national samples of 246,239 non-Hispanic whites, 38,042 blacks and 14,965 Hispanics who were > or = 45 years old at baseline. Mean follow-up of mortality was 5 years (range 1 to 10). RESULTS: During the follow-up period, 27,702 whites (11%), 4,976 blacks (13%) and 1,061 Hispanics (7%) died. Among men, the age-adjusted total mortality per 100,000 person-years was 3,089 in whites and 2,466 in Hispanics, and among women, it was 1,897 and 1,581 in whites and Hispanics, respectively. The Hispanic/white mortality rate ratio for CHD was 0.77 (95% confidence interval [CI] 0.64 to 0.93) and 0.82 (95% CI 0.66 to 1.01) for men and women, respectively. The rate ratio was 0.79 (95% CI 0.68 to 0.91) and 0.80 (95% CI 0.69 to 0.94), respectively, for mortality from cardiovascular diseases. Given the lower all-cause mortality in Hispanics, the proportion of total deaths due to CHD and CVD was similar between the two populations for the same gender and were, respectively, 29.7% and 44.7% in white men, 28.1% and 44.3% in Hispanic men, 24.9% and 43.2% in white women and 24.1% and 41% in Hispanic women. CONCLUSIONS: These data from a cohort of a large national sample are consistent with vital statistics that show that all-cause, CHD and CVD mortality is approximately 20% lower among adult Hispanics than among whites in the United States.

Prevalence of NIDDM among populations of the African diaspora.

OBJECTIVE: Rates of non-insulin-dependent diabetes mellitus have risen sharply in recent years among blacks in the U.S. and the U.K. Increases in risk have likewise been observed in the island nations of the Caribbean and in urban West Africa. To date, however, no systematic comparison of the geographic variation of NIDDM among black populations has been undertaken. RESEARCH DESIGN AND METHODS: In the course of an international collaborative study on cardiovascular disease, we used a standardized protocol to determine the rates of NIDDM and associated risk factors in populations of the African diaspora. Representative samples were drawn from sites in Nigeria, St. Lucia, Barbados, Jamaica, the United States, and the United Kingdom. A total of 4,823 individuals aged 25-74 years were recruited, all sites combined. RESULTS: In sharp contrast to a prevalence of 2% in Nigeria, age-adjusted prevalences of self-reported NIDDM were 9% in the Caribbean and 11% in the U.S. and the U.K. Mean BMI ranged from 22 kg/m2 among men in West Africa to 31 kg/m2 in women in the U.S. Disease prevalence across sites was essentially collinear with obesity, pointing to site differences in the balance between energy intake and expenditure as the primary determinant of differential NIDDM risk among these populations. CONCLUSIONS: In ethnic groups sharing a common genetic ancestry, these comparative data demonstrate the determining influence of changes in living conditions on the population risk of NIDDM.

Relationship between blood pressure and body mass index in lean populations.

Associations between body mass index (BMI) and blood pressure (BP) have been consistently observed, but remain poorly understood. One unresolved question is whether there is a linear relationship across the entire BMI range. We investigated this question among 11,235 adult men and women from seven low-BMI populations in Africa and the Caribbean. We used kernel smoothing and multivariate linear and spline regression modeling to examine gender differences in the relationship and to test for a threshold. Age-adjusted slopes of BP on BMI were uniformly higher in men than women, with pooled slope ratios of 2.00 and 2.20 for systolic and diastolic BPs, respectively. Men displayed no evidence of age modification or nonlinearity in the relationship, and the age-adjusted slope of systolic BP on BMI was 0.90 (95% confidence interval [CI], 0.76 to 1.04). Women demonstrated both age modification and nonlinearity. For both younger (<45 years) and older (45+ years) women, the optimal change point for a single threshold model was found to be 21 kg/m2. Slopes of systolic BP on BMI above this threshold were positive and significant: 0.68 (95% CI, 0.54 to 0.81) and 0.53 (95% CI, 0.29 to 0.76) for younger and older women, respectively. Slopes below the threshold were essentially zero for both groups of women, and the difference between the slopes above and below the threshold was significant for younger women (P=.019). In summary, we observed a threshold at 21 kg/m2 in the relationship between BMI and BP for women but not for men. This contributes to the effort to identify the mechanisms that underlie this relationship and how they differ by gender.

The natural history of incidental renal artery stenosis in patients with aortoiliac vascular disease.

PURPOSE: To examine the association between incidentally discovered renal artery stenosis and deterioration of renal function as determined by the change in serum creatinine concentration over time. SUBJECTS AND METHODS: We performed a retrospective review of consecutive patients who underwent aortography for aortoiliac vascular disease. Angiograms were reviewed for renal artery stenosis, defined as a narrowing of at least 20% compared with adjacent normal renal artery. For patients with at least 180 days of subsequent follow-up, the change in serum creatinine concentration per year was compared in patients who had or did not have renal artery stenosis. RESULTS: Of the 201 patients, 96 (48%) had some degree of renal artery stenosis in one or both renal arteries, including 53 (26%) who had at least one stenosis > or= 50% and 40 (20%) who had bilateral stenoses. The only clinical predictor of renal artery stenosis was a history of coronary artery disease (odds ratio = 2.0, 95% confidence interval: 1.2 to 3.8, P = 0.001). Among the 174 patients with > or =180 days of follow-up, there was no statistically significant difference (P = 0.88) in the mean change in serum creatinine concentration per year in the 78 patients with renal artery stenosis (0.06+/-0.33 mg/dL per year) as compared with the 96 patients without renal artery stenosis (0.06+/-0.22 mg/dL per year). Grouping the patients by the maximal percentage of stenosis did not reveal any difference in the mean changes in serum creatinine concentration per year. CONCLUSIONS: Although renal artery stenosis is a common incidental finding in patients with atherosclerotic vascular disease, it is an uncommon cause of progressive renal disease.

Lifestyle, education, and prevalence of hypertension in populations of African origin. Results from the International Collaborative Study on Hypertension in Blacks.

Lifestyle Incongruity has been shown to be associated with elevated blood pressure in various developing societies. We sought to test this model in an international collaborative study of hypertension in populations of African origin. Data were available for 4770 men and women, aged 25-74, from Africa, the Caribbean, and the United States. The main effects of lifestyle score (LSS) and education on hypertension prevalence were explored, as well as interactions predicted by the Lifestyle Incongruity model. Significant interactions were observed, but only the U.S. men conformed to the pattern predicted. For this group, adjusted ORs for LSS were 4.45 among low-education and 0.71 among high-education subgroups (risk OR = 0.16, 0.03-0.84 95% CI). The Lifestyle Incongruity model therefore received limited support. The model was designed to describe processes in societies experiencing modernization and opportunities for lifestyle differentiation, conditions that may not have been met in some sites.

Detection and clearance of prostate cells subsequent to ultrasound-guided needle biopsy as determined by multiplex nested reverse transcription polymerase chain reaction assay.

OBJECTIVES: To determine if circulating prostate cells are detectable subsequent to transrectal ultrasound (TRUS)-guided biopsy, and if so, whether cells remain in circulation for up to 4 weeks. METHODS: Blood samples were drawn from 90 patients with elevated serum prostate-specific antigen (PSA) levels and/or abnormal digital rectal examination. Two samples were drawn from all patients immediately prior to TRUS and 30 minutes postbiopsy. Blood samples were also obtained 1 week postbiopsy from 83 patients, and 1 month postbiopsy from 61 patients. Multiplex nested reverse transcription polymerase chain reaction assay (RT-PCR) for PSA and prostate-specific membrane antigen (PSM) was performed on total ribonucleic acid (RNA) from each sample. Results were reported as positive if at least one of the targets was detected. RESULTS: Of 45 patients with biopsy-proven adenocarcinoma, 22 were RT-PCR positive prebiopsy and all remained positive 30 minutes postbiopsy. Of 23 patients with adenocarcinoma who were RT-PCR negative prebiopsy, 5 (22%) converted to positive 30 minutes postbiopsy (P < 0.001). Four of these 5 patients returned to negative after 1 week or 1 month. Of 45 patients without cancer at biopsy, 32 were RT-PCR negative prebiopsy and 6 (19%) converted to positive 30 minutes postbiopsy (P < 0.001). Although four of six available samples were still positive at 1 week, all four samples available 1 month postbiopsy were negative. CONCLUSIONS: Detection of circulating prostate cells subsequent to biopsy occurred in 11 of 55 (20%) previously RT-PCR negative patients, a proportion twice that reported in the literature. We attribute this higher proportion to the simultaneous detection of PSA and PSM mRNA in our multiplex assay. Conversion rates were similar in patients regardless of biopsy result. Testing of serial postbiopsy blood demonstrates clearing of these cells by 4 weeks in most patients.

Hypertension in a black population: prevalence and biosocial determinants of high blood pressure in a group of urban Nigerians.

AIMS: To define the prevalence of hypertension, a major cause of morbidity and mortality in blacks, and related biosocial factors in an urban African population group. METHODS: The setting was that of a civil service population in Ibadan, a major city in Southwestern Nigeria. Nine hundred and ninety-eight civil servants selected by multistage sampling participated in the survey. Biosocial data including smoking history, alcohol use and level of physical activity; anthropometry, blood pressure and plasma glucose measurements were obtained. Diagnosis of hypertension was based on blood pressure of > or =160/95 mm Hg or known hypertensive on treatment. RESULTS: The overall prevalence rate of hypertension was 10.3% (CI, 8.4%, 12.2%), rates of 13.9% and 5.3% were obtained in men and women respectively in spite of a much higher rate of generalised obesity in the latter. Hypertension was associated with higher salary grade level, but there was no relationship found with regular exercise, smoking and alcohol. Obesity (body mass index (BMI) > or =30 kg/m2) was associated with hypertension only in women. A two-sided t-test demonstrated age, waist circumference, waist to hip ratio (WHR) and plasma glucose level as significant variables. In multivariate ANOVA models of systolic blood pressures, age, male sex and BMI were highly significant factors (P < 0.0001) and plasma glucose was also significant (P < 0.016); the same variables (except plasma glucose) were associated with diastolic blood pressures. In logistic regression models the variables which predicted hypertension were WHR, plasma glucose, age, sex and family history of diabetes. CONCLUSIONS: Prevalence of hypertension in the study was comparable to recently reported rates in urban Nigeria and similar populations in Africa. The biosocial determinants of hypertension in the urban black population were age, male gender, higher socio-economic status, BMI, plasma glucose, generalised and central adiposity. Regional fat distribution was a stronger predictor of hypertension than generalised obesity in the population.

The mortality risk associated with hypertension: preliminary results of a prospective study in rural Nigeria.

The contribution of hypertension to adult mortality in Africa has not been well studied. Although cross-sectional surveys have provided data on the prevalence of this condition, the relative risk of death associated with hypertension has not been defined. In the face of high levels of competing mortality from infectious disease among the general population, and the virtual absence of atherosclerotic precursors, estimates of risk derived from industrialised countries may not be generalisable to this setting. We conducted a 2-year prospective study among 1344 mean and women in a rural community in south-western Nigeria. The prevalence of hypertension (140/90 mm Hg) at baseline was 9.3%. In the observational phase, 3.0% of the survey participants died each year. Among the 74 decedents, hypertension was nearly twice as common as among those who survived (14.9% vs 8.4%). In multivariate analysis the risk of death increased over 60% for a 20 mm Hg increase in diastolic blood pressure. The population attributable risk, or the reduction in mortality that would have been observed if hypertension were not present in this community, was estimated as 7%. These findings document an identifiable impact of hypertension on all-cause mortality in rural Africa and demonstrate that programs to evaluate potential treatment options are needed.

Hypertension in Cuba: evidence of a narrow black-white difference.

The Caribbean nation of Cuba is comprised of over 10 million persons who trace their ancestry primarily to Africa and Spain. To date, little data on blood pressure (BP) or hypertension prevalence from Cuba have appeared in English language journals. Because the current government has pursued an active policy of reducing social differentiation on the basis of ethnic origin, Cuba provides an important population laboratory from which to advance the understanding of black-white differences in BP and hypertension. The authors conducted a population-based random sample among adults (aged > 15 years) in the city of Cienfuegos. Overall response rate was 95%, yielding 1633 participants who provided BP readings, self-reported racial group, demographic information, and treatment status. Overall prevalence of hypertension (SBP > or = 140 mm Hg or DBP > or = 90 mm Hg or currently treated) was 44% (46% among blacks and 43% whites; P = 0.19). Excess BP among black subjects was reduced slightly by excluding those under treatment, but attained statistical significance after adjustment for sex and age (P = 0.01). The black-white difference was small, however, relative to that observed in the United States. Racial differences in treatment status and control were also observed. Although there remains a difference in socioeconomic profile between those of African and of European origin in Cuba, this has decreased over recent decades. In the United States, the greater magnitude of social differentiation parallels a greater relative risk of BP elevation among blacks, suggesting that social, economic and psychological factors may play an important role in the observed racial gap in cardiovascular risk.

Tuberculosis exposure risk in emergency medicine residents.

OBJECTIVES: To assess purified protein derivative (PPD) test surveillance and respiratory protection practices of emergency medicine (EM) residents, along with the prevalence of PPD test conversion and the development of active tuberculosis (TB) in EM residents. METHODS: The study instrument was an anonymous, self-reporting, multiple-choice survey administered to U.S. and Canadian EM residents. It was distributed for voluntary completion in conjunction with the American Board of Emergency Medicine's annual in-service examination, which was administered February 25, 1998. RESULTS: A total of 89.3% (n = 2,985) of residents eligible to complete the survey completed at least part of it. The majority of residents are PPD-tested once a year. The prevalence of PPD test conversions in EM residents was between 1.4% (36/2,575) and 2.0% (52/2,575). Of the residents who PPD test-converted, the ED was most often the perceived area of TB source exposure (n = 15). Two residents (0.08%) reported having developed active TB, including chest radiographic findings or clinical infection, which equals a 0.14% (95% CI = 0.005 to 0.31) risk of developing active TB over a three-year residency. Half of all the residents do not routinely wear National Institute for Occupational Safety and Health (NIOSH)-approved particulate filtration respirator (PFR) masks in patient encounters at risk for TB exposure. While more than a third of EM residents have not undergone fit testing for a NIOSH-approved PFR mask, the lack of routine easy availability of such masks is the most common reason they are not routinely worn by EM residents during at-risk encounters for TB transmission. CONCLUSIONS: Most surveillance PPD testing of EM residents is performed at intervals recommended by the CDC. TB control programs at institutions sponsoring EM residencies need to improve both compliance with PFR mask fit testing by EM residents and availability of approved PFR masks in appropriate areas of the ED. Despite poor compliance with personal respiratory protection in ED patient encounters at risk for TB transmission, the risk of an EM resident's developing active TB over a three-year residency is low.

In search of the hypothesis.

Epidemiologic studies of racial differences sorely lack sound and explicit hypotheses. Race is a social convention, not a biological concept. Its careless use in epidemiology demonstrates a failure to generate appropriate hypotheses to study its role in health. Studies of hypertension in blacks illustrate the point. Two underlying pitfalls plague hypothesis generation: directionality involving the null and alternative hypotheses and circularity, where efforts to understand social factors have the effect of emphasizing racial differences. The proper prescription is to identify explicitly the hypotheses of interest, including their origins and implication.

A micro-kininogenase assay for studies of kallikrein in renal micropuncture/microperfusion.

We report the development of a micro-kininogenase assay suitable in studying the dynamics of kallikrein at intranephron segmental level. The detection limit is 119 fg or 2.6 attomoles of kallikrein. Activation of microquantities of kallikrein is possible with the use of Triton X-100. Because of its extremely high sensitivity and reproducibility the assay is likely to also prove useful in physiological studies in which only very small amounts of kallikrein containing samples can be obtained.