Urinary cotinine and parent history (questionnaire) as indicators of passive smoking and predictors of lower respiratory illness in infants.

Studies of the effects of passive smoking on lower respiratory illness (LRI) have relied on questionnaires to measure exposure. We studied the association between two measures of passive smoking and the incidence of acute LRI in infants. We analyzed data from a community-based cohort study of respiratory illness during the first year of life in North Carolina. The incidence of LRI was determined by telephone calls at 2-week intervals. Environmental, demographic, and psychosocial risk factors for LRI were measured during home interviews. Tobacco smoke exposure was measured as the mean number of cigarettes smoked per day in the infant's presence. Smoke absorption by the infants was measured by the urinary cotinine/ creatinine ratio. Of the 485 infants in the study, 325 (67%) had telephone follow-up and at least two home interviews. In bivariate analyses, reported tobacco smoke exposure and urinary cotinine were associated with LRI. Only the association between reported exposure and LRI remained significant after adjusting for confounders, [adjusted incidence of LRI (episodes/child-year) non-exposed: 0.6; < or = 10 cigarettes/day: 0.9 (RR 1.5, 95% CI: 1.1, 2.0); > 10 cigarettes/day: 1.3 (RR 2.2, 95% CI: 1.3, 3.8)]. We conclude that infants reportedly exposed to tobacco smoke have an increased incidence of LRI. There are differences between questionnaire and biochemical measures of passive smoking. Urinary cotinine will not necessarily improve the validity of studies of the relationship of passive smoking to LRI in infants.

Linking clinical and public health approaches to improve access to health care for socially disadvantaged mothers and children. A feasibility study.

OBJECTIVE: To test the feasibility of combining home- and office-based interventions to improve access to health care and health outcomes of Medicaid-eligible mothers and infants. DESIGN: Randomized trial in 2 counties in North Carolina (1 rural, 1 urban). Information on health and developmental outcomes was obtained by face-to-face interviews, medical chart abstractions, hospital medical records, and state data tapes. PARTICIPANTS: Ninety-three Medicaid-eligible first-time pregnant women in their third trimester and their subsequently born infants, who were followed up until they were 6 months old, and 3 pediatric practices and 1 family practice. INTERVENTIONS: Coordinated home visit and office intervention, office intervention, and usual care. Home visits by 3 public health nurses provided parental education and social support and linked families with needed community resources. Women in the office intervention group were encouraged to seek health care for their infants from one of the primary care practices. Participating offices received assistance with Medicaid billing, help developing a system to improve preventive care, and customized patient education materials. RESULTS: Mothers reported that the nurses helped them in areas related to the content of the program. An office system for prevention was developed and implemented in all 4 practices for study patients. Families in the intervention groups were more likely than control families to have had a prenatal visit with a pediatrician (P = .01, chi 2), a primary care office as the regular source of sick care (P = .02, chi 2), and less waiting time (P = .02, Student t test). They were also more likely to recall receiving patient education materials (P = .007, chi 2). CONCLUSIONS: It is feasible to link clinical and public health approaches to improve the quality and effectiveness of care for socially disadvantaged children. Such interventions should be tested in defined populations.

Evaluation of a home-based intervention program to reduce infant passive smoking and lower respiratory illness.

We conducted a randomized controlled trial to determine whether a home-based intervention program could reduce infant passive smoking and lower respiratory illness. The intervention consisted of four nurse home visits during the first 6 months of life, designed to assist families to reduce the infant's exposure to tobacco smoke. Among the 121 infants of smoking mothers who completed the study, there was a significant difference in trend over the year between the intervention and the control groups in the amount of exposure to tobacco smoke; infants in the intervention group were exposed to 5.9 fewer cigarettes per day at 12 months. There was no group difference in infant urine cotinine excretion. The prevalence of persistent lower respiratory symptoms was lower among intervention-group infants of smoking mothers whose head of household had no education beyond high school: intervention group, 14.6%; and controls, 34.0%.

Accuracy of the clinical examination in detecting hypoxemia in infants with respiratory illness.

OBJECTIVES: To evaluate the diagnostic accuracy of the clinical examination in detecting hypoxemia in infants with lower respiratory tract illness. DESIGN: Cross-sectional study. SETTING: Three university pediatric outpatient departments and one private pediatric practice. PATIENTS: Healthy infants less than 1 year of age seen between December and March 1989 and 1990, with symptoms suggesting acute lower respiratory tract illness. MAIN OUTCOME MEASURES: The test characteristics of 27 elements of the clinical examination, as well as the accuracy of the overall examination and the components of the examination in detecting oxygen saturation < 95% measured by pulse oximetry. Reliability of clinical examination findings. RESULTS: None of the 27 clinical findings had sensitivities that would make them useful diagnostic tests for hypoxemia. By combining all the clinical findings, however, we found good diagnostic accuracy (area under the receiver operator characteristic curve 0.90). Three groups of clinical findings--social interactiveness, respiratory effort, and physical appearance--accounted for much of the diagnostic accuracy of the examination. Auscultatory findings contributed little. In these three groups, five clinical findings accounted for almost all the accuracy: attentiveness, consolability, respiratory effort, color, and movement. Together, these findings also had good accuracy (area under the receiver operator characteristic curve 0.95). CONCLUSIONS: A small number of clinical observations may be mostly responsible for the diagnostic value of the clinical examination of infants with symptoms of LRI. Concentrating on a limited group of findings appears to enhance the accuracy of the examination in detecting hypoxemia.

Application of sample survey methods for modelling ratios to incidence densities.

We describe ratio estimation methods for multivariately analysing incidence densities from prospective epidemiologic studies. Commonly used in survey data analysis, these ratio methods require minimal distributional assumptions and take into account the random variability in the at-risk periods. We illustrate their application with data from a study of lower respiratory illness (LRI) in children during the first year of life. One question of interest is whether children with passive exposure to tobacco smoke have a higher rate of LRI, on average, than those with no exposure and in a setting where age of child and season are taken into account. A second question is whether the relationship persists after adjusting for background variables such as family's socioeconomic status, crowding in the home, race, and type of feeding. The basic strategy consists of a two-step process in which we first estimate subgroup-specific incidence densities and their covariance matrix via a first-order Taylor series approximation. These estimates are used to test for differences in marginal rates of LRI between children exposed to tobacco smoke and those not exposed. We then fit a log-linear model to the estimated ratios in order to test for significant covariate effects. The ability to produce direct estimates of adjusted incidence density ratios for risk factors of interest is an important advantage of this approach. For comparison purposes and to address the limitations of the ratio method with respect to the number of covariates that can be controlled simultaneously, we consider survey logistic regression methods for the example data as well as logistic and Poisson regression models fitted via generalized estimating equation methods. Although the analysis strategy is illustrated with illness data from an epidemiologic study, the context of application is broader and includes, for example, data on adverse events from a clinical trial.

Lower respiratory illness in infants and low socioeconomic status.

OBJECTIVES: Infants from families of low socioeconomic status are said to suffer higher rates of lower respiratory illness, but this assertion has not been carefully examined. METHODS: We studied the frequency and determinants of lower respiratory illness in infants of different socioeconomic status (n = 393) by analyzing data from a community-based cohort study of respiratory illness during the first year of life in central North Carolina. RESULTS: The incidence of lower respiratory illness was 1.41 in the low socioeconomic group, 1.26 in the middle group, and 0.67 in the high group. The prevalence of persistent respiratory symptoms was 39% in infants in the low socioeconomic group, 24% in infants in the middle group, and 14% in infants in the high group. The odds of persistent respiratory symptoms in infants of low and middle socioeconomic status were reduced after controlling for environmental risk factors for lower respiratory illness. Enrollment in day care was associated with an increased risk of persistent symptoms among infants of high but not low socioeconomic status. CONCLUSIONS: Infants of low socioeconomic status are at increased risk of persistent respiratory symptoms. This risk can be partly attributed to environmental exposures, most of which could be changed.

Factors associated with pediatricians' participation in Medicaid in North Carolina.

OBJECTIVE: To describe the relative importance of factors influencing pediatricians' participation in Medicaid in North Carolina. DESIGN: Questionnaire survey. SETTING AND PARTICIPANTS: Nonacademic primary care pediatricians in direct patient care at least 50% of the time; 332 (85%) of the 389 eligible pediatricians responded. MAIN OUTCOME MEASURES: Proportion of pediatricians who restricted Medicaid patients' access to their practices. The association between restricting access and the following factors was assessed: Medicaid reimbursement, pediatricians' demographic characteristics, knowledge of the Medicaid program, attitudes toward Medicaid patients and the Medicaid program, and beliefs about whether other physicians were available to care for Medicaid patients. RESULTS: Twenty-nine percent of pediatricians restricted Medicaid patients' access to their practices. The proportion of pediatricians restricting access was 62% in cities, 13% in medium-sized towns, and 12% in small towns (P less than .001), but the proportion of pediatricians in cities who restricted access varied from 87% to 22%. Pediatricians who received a higher proportion of their usual fee were less likely to restrict Medicaid patients' access. The relationship between Medicaid payment and restricted access was substantially weakened after controlling for the following factors: (1) the size of the community, (2) pediatricians' attitudes toward Medicaid payment, (3) their perceptions that they were too busy to care for Medicaid patients, and (4) whether there were other resources for the care of Medicaid patients. At comparable levels of payment, rural pediatricians were about six times less likely than urban pediatricians to restrict access. Pediatricians who knew less about Medicaid reimbursement also restricted access more often. Whether or not they restricted access to new Medicaid patients, pediatricians provided acute, preventive, hospital, and emergency care to the Medicaid patients who were already in their practices. CONCLUSIONS: Existing resources for the care of Medicaid patients, pediatricians' economic dependence on Medicaid, and the local norms of practice may be important factors in pediatricians' decision to participate in Medicaid. Increasing reimbursement will have only modest effects on Medicaid participation. Strategies to improve participation should also address pediatricians' knowledge of the Medicaid program and enlist the support of community physicians.

Passive smoking during the first year of life.

BACKGROUND AND PURPOSE: A description of passive smoking during the first year of life might assist planning preventive efforts. METHODS: Changes in the ecology of passive smoking were investigated in a sample of infants in central North Carolina followed from birth to one year of age. RESULTS: The prevalence of tobacco smoke absorption, indicated by excretion of cotinine, increased from 53 percent to 77 percent (95% CI of difference: 14, 35) during the first year of life. Most infants (92 percent) excreting cotinine at three weeks of age were also excreting it at one year. Moreover, 61 percent of infants not excreting cotinine at age three weeks were excreting it at one year. This increase reflected an increased exposure to household and, particularly, nonhousehold sources of smoke; the proportion of infants exposed to nonhousehold smokers increased from 14 percent to 36 percent. CONCLUSIONS: These findings suggest that prevention of the onset of passive smoking should begin very early.

Natural killer activity in Fischer-344 rat lungs as a method to assess pulmonary immunocompetence: immunosuppression by phosgene inhalation.

Phosgene, also known as carbonyl chloride, carbon oxychloride, and chloroformyl chloride, is a toxic air pollutant and a potential occupational health hazard. Studies were initiated (a) to evaluate the measurement of pulmonary natural killer (NK) activity as a method to assess pulmonary immunocompetence, and (b) to determine whether exposure to phosgene resulted in local pulmonary or systemic immune dysfunction. Fischer-344 male rats were exposed either to filtered air or to 1.0 ppm phosgene gas for four hours. The effect of phosgene on lung NK activity was quantified at different times after acute phosgene exposure. Pulmonary NK activity was measured by mincing lung tissue into small pieces prior to incubation with collagenase. Whole-lung homogenate was assayed for NK activity utilizing a 4 hour 51-Cr-release assay with YAC-1 cells as target cells. Acute phosgene exposure resulted in a suppressed pulmonary NK activity on days 1, 2, and 4 after exposure; however, normal levels of biological activity were observed 7 days after exposure. The suppressed NK activity was not restored after removal of adherent cells from the lung homogenate, thus indicating that the effect of phosgene on NK activity was not due to immunosuppression via mobilization of suppressor alveolar macrophages. Pulmonary immunotoxicity was also observed after exposure at 0.5 ppm, while no adverse effects were observed at 0.1 ppm phosgene. Systemic immunotoxic effects were observed for NK activity in the spleen, but not in the peripheral blood. It is thus important in pulmonary immunotoxicology to evaluate systemic immune functions, since secondary effects--distant to the original interaction--may occur with potentially serious consequences. Cells exhibiting natural killer activity comprise a part of the nonspecific innate immunity that is important in defense against both neoplastic and viral diseases. Any perturbation of this important nonspecific immunological mechanism may result in a compromised host more susceptible to infectious and neoplastic disease.

Immunosuppression of pulmonary natural killer activity by exposure to ozone.

Ozone is an oxidant gas and an ubiquitous oxidant air pollutant with the potential to adversely affect pulmonary immune function with a consequent increase in disease susceptibility. Pulmonary natural killer (NK) activity was measured in order to assess the pulmonary immunotoxicity of continuous ozone exposure. Continuous ozone exposures at 1.0 ppm were performed for 23.5 hours per day for either 1, 5, 7, or 10 consecutive days. Pulmonary immune function was assessed by measuring natural killer (NK) activity from whole-lung homogenates of male Fischer-344 rats. Results of this study indicated that continuous ozone exposure for 1, 5, or 7 days resulted in a significant decrease in pulmonary NK activity. This suppressed pulmonary NK activity returned to control levels after continuous exposure to ozone for 10 days. The suppressed pulmonary NK response was thus attenuated and returned to normal values in the continued presence of ozone gas. This attenuation process is dynamic, complex, and doubtless involves several cell types and/or products of these cells. Pulmonary NK activity was also suppressed at 0.5 ppm ozone, but not at 0.1 ppm ozone, following 23.5 hours of exposure. NK activity is important for defense against viral, bacterial, and neoplastic disease. The depressed NK activity resulting from continuous ozone exposure could therefore result in a compromised ability to defend against pulmonary diseases.

The effect of general anesthesia on canine lymphocyte function.

The in vitro response of canine peripheral blood lymphocytes to mitogenic stimulation was evaluated following general anesthesia for a relatively minor diagnostic procedure. A marked suppression in the blastogenic response to phytohemagglutinin and concanavalin A was observed 4 hours postinduction which persisted through the first 24 hours and was normal by 4 days. A mild suppression to stimulation with pokeweed mitogen was observed at 4 hours postinduction but the response was back to normal by 24 hours. These results suggest general anesthesia has a transient immunosuppressive effect on canine lymphocytes and T cells are more susceptible to the immunosuppressive effect than B cells.

Determination of relative antigen-antibody affinities by quantitative immunoelectrophoresis.

The relative affinities of an antibody population of different antigens or of different antibody populations for one antigen can be determined by quantitative immunoelectrophoresis. Antigen-antibody interactions of greater average affinity result in a greater increase in rocket area as a function of the amount of antigen applied to the wells. This is measured as the slope of the line in plots of rocket area versus antigen amount. Quantitative immunoelectrophoresis of different antigens, which nevertheless have the same affinity for antibody, produces plots with the same slopes. The relative magnitudes of the slopes of these lines reflect the relative average affinities of different antibody populations for an antigen.