Structural equation modeling of the medical outcome study: Short Form 36 (SF-36)

The factorial validity of the SF-36 was evaluated using confirmatory factor analysis (CFA) methods, structural equation modeling (SEM), and multigroup structural equation modeling (MSEM). First, the measurement and structural model of the hypothesized SF-36 was explicated. Second, the model was tested for the validity of a second-order factorial structure, upon evidence of model misfit, determined the best-fitting model, and tested the validity of the best-fitting model on a second random sample from the same population. Third, the best-fitting model was tested for invariance of the factorial structure across race, age, and educational subgroups using MSEM.^ The findings support the second-order factorial structure of the SF-36 as proposed by Ware and Sherbourne (1992). However, the results suggest that: (a) Mental Health and Physical Health covary; (b) general mental health cross-loads onto Physical Health; (c) general health perception loads onto Mental Health instead of Physical Health; (d) many of the error terms are correlated; and (e) the physical function scale is not reliable across these two samples. This hierarchical factor pattern was replicated across both samples of health care workers, suggesting that the post hoc model fitting was not data specific. Subgroup analysis suggests that the physical function scale is not reliable across the "age" or "education" subgroups and that the general mental health scale path from Mental Health is not reliable across the "white/nonwhite" or "education" subgroups.^ The importance of this study is in the use of SEM and MSEM in evaluating sample data from the use of the SF-36. These methods are uniquely suited to the analysis of latent variable structures and are widely used in other fields. The use of latent variable models for self reported outcome measures has become widespread, and should now be applied to medical outcomes research. Invariance testing is superior to mean scores or summary scores when evaluating differences between groups. From a practical, as well as, psychometric perspective, it seems imperative that construct validity research related to the SF-36 establish whether this same hierarchical structure and invariance holds for other populations.^ This project is presented as three articles to be submitted for publication. ^

Risk factors associated with first symptomatic infection of {\it Cryptosporidium parvum\/} in an infant population in Bilbeis, Egypt

Diarrhea disease is a leading cause of morbidity and mortality, especially in children in developing countries. An estimate of the global mortality caused by diarrhea among children under five years of age was 3.3 million deaths per year. Cryptosporidium parvum was first identified in 1907, but it was not until 1970 that this organism was recognized as a cause of diarrhea in calves. Then it was as late as 1976 that the first reported case of human Cryptosporidiosis occurred. This study was conducted to ascertain the risk factors of first symptomatic infection with Cryptosporidium parvum in a cohort of infants in a rural area of Egypt. The cohort was followed from birth through the first year of life. Univariate and multivariate analyses of data demonstrated that infants greater than six months of age had a two-fold risk of infection compared with infants less than six months of age (RR = 2.17; 95% C.I. = 1.01-4.82). When stratified, male infants greater than six months of age were four times more likely to become infected than male infants less than six months of age. Among female infants, there was no difference in risk between infants greater than six months of age and infants less than six months of age. Female infants less than six months of age were twice more likely to become infected than male infants less than six months of age. The reverse occurred for infants greater than six months of age, i.e., male infants greater than six months of age had twice the risk of infection compared to females of the same age group. Further analysis of the data revealed an increased risk of Cryptosporidiosis infection in infants who were attended in childbirth by traditional childbirth attendants compared to infants who were attended by modern childbirth attendants (nurses, trained midwives, physicians) (RR = 4. 18; 95% C.I. = 1.05-36.06). The final risk factor of significance was the number of people residing in the household. Infants in households which housed more than seven persons had an almost two-fold risk of infection compared with infants in homes with fewer than seven persons. Other risk factors which suggested increased risk were lack of education among the mothers, absence of latrines and faucets in the homes, and mud used as building material for walls and floors in the homes. ^

The angiotensin-converting enzyme insertion/deletion polymorphism and its associations with carotid artery wall thickness and coronary heart disease: The atherosclerosis risk in communities study

Coronary heart disease (CHD) is the leading cause of death in the United States. Recently, renin-angiotensin system (RAS) was found associated with atherosclerosis formation, with angiotensin II inducing vascular smooth muscle cell growth and migration, platelet activation and aggregation, and stimulation of plasminogen activator inhibitor-1. Angiotensin II is converted from angiotensin I by angiotensin I-converting enzyme (ACE) and this enzyme is mainly genetically determined. The ACE gene has been assigned to chromosome 17q23 and an insertion/deletion (I/D)polymorphism has been characterized by the presence/absence of a 287 bp fragment in intron 16 of the gene. The two alleles form three genotypes, namely, DD, ID and II and the DD genotype has been linked to higher plasma ACE levels and cell ACE activity.^ In this study, the association between the ACE I/D polymorphism and carotid artery wall thickness measured by B-mode ultrasound was investigated in a biracial sample, and the association between the gene and incident CHD was investigated in whites and if the gene-CHD association in whites, if any, was due to the gene effect on atherosclerosis. The study participants are from the prospective Atherosclerosis Risk in Communities (ARIC) Study, including adults aged 45 to 65 years. The present dissertation used a matched case-control design for studying the associations of the ACE gene with carotid artery atherosclerosis and an unmatched case-control design for the association of the gene with CHD. A significant recessive effect of the D allele on carotid artery thickness was found in blacks (OR = 3.06, 95% C.I: 1.11-8.47, DD vs. ID and II) adjusting for age, gender, cigarette smoking, LDL-cholesterol and diabetes. No similar associations were found in whites. The ACE I/D polymorphism is significantly associated with coronary heart disease in whites, and while stratifying data by carotid artery wall thickness, the significant associations were only observed in thin-walled subgroups. Assuming a recessive effect of the D allele, odds ratio was 2.84 (95% C.I:1.17-6.90, DD vs. ID and II) and it was 2.30 (95% C.I:1.22-4.35, DD vs. ID vs. II) assuming a codominant effect of the D allele. No significant associations were observed while comparing thick-walled CHD cases with thin-walled controls. Following conclusions could be drawn: (1) The ACE I/D polymorphism is unlikely to confer appreciable increase in the risk of carotid atherosclerosis in US whites, but may increases the risk of carotid atherosclerosis in blacks. (2) ACE I/D polymorphism is a genetic risk factor for incident CHD in US whites and this effect is separate from the chronic process of atherosclerosis development. Finally, the associations observed here are not causal, since the I/D polymorphism is in an intron, where no ACE proteins are encoded. ^

HIV-related malignancies: A community-based study using a linkage of cancer registry and HIV registry data

Background. Increased incidence of cancer is documented in immunosuppressed transplant patients. Likewise, as survival increases for persons infected with the Human Immunodeficiency Virus (HIV), we expect their incidence of cancer to increase. The objective of this study was to examine the current gender specific spectrum of cancer in an HIV infected cohort (especially malignancies not currently associated with Acquired Immunodeficiency Syndrome (AIDS)) in relation to the general population.^ Methods. Cancer incidence data was collected for residents of Harris County, Texas who were diagnosed with a malignancy between 1975 and 1994. This data was linked to HIV/AIDS registry data to identify malignancies in an HIV infected cohort of 14,986 persons. A standardized incidence ratio (SIR) analysis was used to compare incidence of cancer in this cohort to that in the general population. Risk factors such as mode of HIV infection, age, race and gender, were evaluated for contribution to the development of cancer within the HIV cohort, using Cox regression techniques.^ Findings. Of those in the HIV infected cohort, 2289 persons (15%) were identified as having one or more malignancies. The linkage identified 29.5% of these malignancies (males 28.7% females 60.9%). HIV infected men and women had incidences of cancer that were 16.7 (16.1, 17.3) and 2.9 (2.3, 3.7) times that expected for the general population of Harris County, Texas, adjusting for age. Significant SIR's were observed for the AIDS-defining malignancies of Kaposi's sarcoma, non-Hodgkin's lymphoma, primary lymphoma of the brain and cancer of the cervix. Additionally, significant SIR's for non-melanotic skin cancer in males, 6.9 (4.8, 9.5) and colon cancer in females, 4.0 (1.1, 10.2) were detected. Among the HIV infected cohort, race/ethnicity of White (relative risk 2.4 with 95% confidence intervals 2.0, 2.8) or Spanish Surname, 2.2 (1.9, 2.7) and an infection route of male to male sex, with, 3.0 (1.9, 4.9) or without, 3.4 (2.1, 5.5) intravenous drug use, increased the risk of having a diagnosis of an incident cancer.^ Interpretation. There appears to be an increased risk of developing cancer if infected with the HIV. In addition to the malignancies routinely associated with HIV infection, there appears to be an increased risk of being diagnosed with non-melanotic skin cancer in males and colon cancer in females. ^

A quality of life subscale for terminally ill cancer patients

A subscale was developed to assess the quality of life of cancer patients with a life expectancy of six months or less. Phase I of this study identified the major concerns of 74 terminally ill cancer patients (19 with breast cancer, 19 with lung cancer, 18 with colorectal cancer, 9 with renal cell cancer, 9 with prostate cancer), 39 family caregivers, and 20 health care professionals. Patients interviewed were being treated at the University of Texas M. D. Anderson Cancer Center or at the Hospice at the Texas Medical Center in Houston. In Phase II, 120 patients (30 with breast cancer, 30 with lung cancer, 30 with colorectal cancer, 15 with prostate cancer, and 15 with renal cell cancer) rated the importance of these concerns for quality of life. Items retained for the subscale were rated as "extremely important" or "very important" by at least 60% of the sample and were reported as being applicable by at least two-thirds of the sample. The 61 concerns that were identified were formatted as a questionnaire for Phase III. In Phase III, 356 patients (89 with breast cancer, 88 with lung cancer, 88 with colorectal cancer, 44 with prostate cancer, and 47 with renal cell cancer) were interviewed to determine the subscale's reliability and sensitivity to change in clinical status. Both factor analysis and item response theory supported the inclusion of the same 35 items for the subscale. Internal consistency reliability was moderate to high for the subscale's domains: spiritual (0.87), existential (0.76), medical care (0.68), symptoms (0.67), social/family (0.66), and emotional (0.61). Test-retest correlation coefficients also were high for the domains: social/family (0.86), emotional (0.83), medical care (0.83), spiritual (0.75), existential (0.75), and symptoms (0.81).^ In addition, concurrent validity was supported by the high correlation between the subscale's symptom domain and symptom items from the European Organization for Research and Treatment of Cancer (EORTC) scale (r = 0.74). Patients' functional status was assessed with the Eastern Cooperative Oncology Group (ECOG) Performance status rating. When ECOG categories were compared to subscale domains, patients who scored lower in functional status had lower scores in the spiritual, existential, social/family, and emotional domains. Patients who scored lower in physical well-being had higher scores in the symptom domain. Patient scores in the medical care domain were similar for each ECOG category. The results of this study support the subscale's use in assessing quality of life and the outcomes of palliative treatment for cancer patients in their last six months of life. ^

A study of the impact of cigarette advertising on adolescent susceptibility to smoking among 5th-, 8th-, and 12th-grade students in Hempstead and Hitchcock Independent School Districts

This study assessed the impact of cigarette advertising on adolescent susceptibility to smoking in the Hempstead and Hitchcock Independent School Districts. A convenience sample of 217 youths, 10-19 years of age was recruited in the study. Students completed both a paper-and-pencil and a computer-aided questionnaire in April 1996. Adolescents were defined as susceptible to smoking if they could not definitely rule out the possibility of future smoking. For the analysis, an index was devised: a 5-point index of an individual's receptivity to cigarette advertising. The index is determined by the number of positive responses to five survey items (recognizing cigarette brand logos, recognizing cigarette advertisement's pictures, recognizing cigarette brand slogans, evaluating adolescent attitudes toward cigarette advertising, and the degree to which adolescents were exposed to cigarette advertisements). Using logistic regression, we assessed the independent importance of the index in predicting susceptibility to smoking and ever smoking after adjusting for sociodemographic variables, perceived school performance and family composition. Of students surveyed, 54.4% of students appeared to have started the smoking uptake process as measured by susceptibility to smoking. Camel was recognized by the majority of students (88%), followed by Marlboro (41.5%) and Newport (40.1%). The pattern for recognition of the cigarette advertisements was the same as the pattern of market for cigarette. Advertisement featuring the cartoon character Joe Camel was significantly more appealing to adolescents than were advertisements with human models, with animal models, and with text only (p $<$ 0.001). Text only advertisement was significantly less appealing than other types of advertisements. The cigarette advertisement with White models (Marlboro) had significantly higher appeal to White students than to African-American students (p $<$ 0.001). The cigarette advertisement featuring African-American models (Virginia Slims) was significantly more appealing to African-American students than other ethnic groups (p $<$ 0.001). Receptivity to cigarette advertising was to be an important concurrent predictor of past smoking experience and intention to smoke in the future. Adolescents who scored in the fourth quartile of the Index of Receptivity to Cigarette Advertising were 7.54 (95% confidence interval (CI) = 1.92-29.56) times as likely to be susceptible to smoking, and were 4.56 (95% CI = 1.55-13.38) times as likely to have tried smoking, as those who scored in the first quartile of the Index. The findings confirmed the hypothesis that cigarette advertising may be a strong current influence in encouraging adolescents to initiate the smoking uptake process than sociodemographic variables, perceived school performance and family composition. ^

An evaluation of a community-based program for homeless adults with mental disorders and comorbid alcohol drug and mental disorders

Limited research has been conducted evaluating programs that are designed to improve the outcomes of homeless adults with mental disorders and comorbid alcohol, drug and mental disorders. This study conducted such an evaluation in a community-based day treatment setting with clients of the Harris County Mental Health and Mental Retardation Authority's Bristow Clinic. The study population included all clients who received treatment at the clinic for a minimum of six months between January 1, 1995 and August 31, 1996. An electronic database was used to identify clients and to track their program involvement. A profile was developed of the study participants and their level of program involvement included an examination of the amount of time spent in clinical, social and other interventions, the type of interventions encountered and the number of interventions encountered. Results were analyzed to determine whether social, demographic and mental history affected levels of program involvement and the effects of the levels of program involvement on housing status and psychiatric functioning status.^ A total of 101 clients met the inclusion criteria. Of the 101 clients, 96 had a mental disorder, and five had comorbidity. Due to the limited numbers of participants with comorbidity, only those with mental disorders were included in the analysis. The study found the Bristow Clinic population to be primarily single, Black, male, between the ages of 31 and 40 years, and with a gross family income of less than $4,000. There were more persons residing on the streets at entry and at six months following treatment than in any other residential setting. The most prevalent psychiatric diagnoses were depressive disorders and schizophrenia. The Global Assessment of Functioning (GAF) scale which was used to determine the degree of psychiatric functioning revealed a modal GAF score of 31--40 at entry and following six months in treatment. The study found that the majority of clients spent less than 17 hours in treatment, had less than 51 encounters and had clinical, social, and other encounters. In regard to social and demographic factors and levels of program involvement, there were statistically significant associations between gender and ethnicity and the types of interventions encountered as well as the number of interventions encountered. There was also a statistically significant difference between the amount of time spent in clinical interventions and gender. Relative to outcomes measured, the study found female gender to be the only background variable that was significantly associated with improved housing status and the female gender and previous MHMRA involvement to be statistically associated with improvement in GAF score. The total time in other (not clinical or social) interventions and the total number of encounters with other interventions were also significantly associated with improvement in housing outcome. The analysis of previous services and levels of program involvement revealed significant associations between time spent in social and clinical interventions and previous hospitalizations and previous MHMRA involvement.^ Major limitations of this study include the small sample size which may have resulted in very little power to detect differences and the lack of generalizability of findings due to site locations used in the study. Despite these limitations, the study makes an important contribution to the literature by documenting the levels of program involvement and the social and demographic factors necessary to produce outcomes of improved housing status and psychiatric functioning status. ^

Incidence, etiology and risk factors of neonatal seizures Harris County, Texas, 1992--1994

This study was conducted to determine the incidence and etiology of neonatal seizures, and evaluate risk factors for this condition in Harris County, Texas, between 1992 and 1994. Potential cases were ascertained from four sources: discharge diagnoses at local hospitals, birth certificates, death certificates, and a clinical study of neonatal seizures conducted concurrent with this study at a large tertiary care center in Houston, Texas. The neonatal period was defined as the first 28 days of life for term infants, and up to 44 weeks gestation for preterm infants.^ There were 207 cases of neonatal seizures ascertained among 116,048 live births, yielding and incidence of 1.8 per 1000. Half of the seizures occurred by the third day of life, 70% within the first week, and 93% within the first 28 days of life. Among 48 preterm infants with seizures 15 had their initial seizure after the 28th day of life. About 25% of all seizures occurred after discharge from the hospital of birth.^ Idiopathic seizures occurred most frequently (0.5/1000 births), followed by seizures attributed to perinatal hypoxia/ischemia (0.4/1000 births), intracranial hemorrhage (0.2/1000 births), infection of the central nervous system (0.2/1000 births), and metabolic abnormalities (0.1/1000 births).^ Risk factors were evaluated based on birth certificate information, using univariate and multivariate analysis (logistic regression). Factors considered included birth weight, gender, ethnicity, place of birth, mother's age, method of delivery, parity, multiple birth and, among term infants, small birth weight for gestational age (SGA). Among preterm infants, very low birth weight (VLBW, $<$1500 grams) was the strongest risk factor, followed by birth in private/university hospitals with a Level III nursery compared with hospitals with a Level II nursery (RR = 2.9), and male sex (RR = 1.8). The effect of very low birth weight varied according to ethnicity. Compared to preterm infants weighing 2000-2999 grams, non-white VLBW infants were 12.0 times as likely to have seizures; whereas white VLBW infants were 2.5 times as likely. Among term infants, significant risk factors included SGA (RR = 1.8), birth in Level III nursery private/university hospitals versus hospitals with Level II nursery (RR = 2.0), and birth by cesarean section (RR = 2.2). ^

Birth defects among surviving children under seven years of age in Tianjin, China

Birth defects are a leading cause of infant mortality in the developed countries. They are also of increasing concern in many developing countries, such as China. However, prevalence and causes of birth defects in China are inadequately understood.^ The purpose of the present study was to estimated prevalence of birth defects in surviving children under seven years of age in Tianjin, China and investigate determinants of birth defects in the study area.^ The present study took place in Tianjin, China in 1986, involving 22,081 surviving children under seven years of age. Children with birth defects were ascertained through physical examinations by physicians during household visits and ascertainment of birth defects was verified through multiple sources. Of 22,081 surviving children, 524 had birth defects (23.7 per 1,000). The study noted a striking discrepancy in the prevalence of birth defects between urban and rural area. The prevalence of birth defects was 16.3 per 1,000 in the urban and 33.2 per 1,000 in the rural area.^ Using cases of birth defects ascertained from surviving children, a case-control study was carried out. The study observed that first-trimester maternal flu was associated with increased risk of both major and minor birth defects in children after controlling for other maternal factors (adjusted odds ratio (OR) = 8.7, 95% confidence interval (CI) = 4.3-17.3; OR = 3.6, 95% CI = 1.7-7.5). This association could be biased by different reporting of exposure between mothers of children with birth defects and mothers of children without defects. This study indicated that maternal flu was also associated with congenital heart defects and polydactyly after controlling for other maternal factors (adjusted OR = 32.3, 95% CI = 13.3-78.3; adjusted OR = 5.5, 95% CI = 1.1-27.7). The associations remained when affected controls (children with similar birth defects other than congenital heart defects or polydactyly) were used (adjusted OR = 4.3, 95% CI = 1.2-15.3; OR = 1.4, 95% CI = 1.4-7.9). A weak association between first-trimester vaginal bleeding and selected groups of birth defects was found in this study, but the association may be confounded by other factors. Maternal smoking during pregnancy was modestly associated with cleft lip with or without cleft palate (OR = 1.4, 95% = 0.4-4.9), but the association may be due to chance. Some major limitations in this study warrant caution in interpretation of the findings, especially the causal relation. ^

Psychiatric severity and behavior change in alcoholism

Individuals who are diagnosed with a chronic mental illness and an alcohol use disorder comprise a high risk population that challenges the mental health care system. Effective treatment for the dually diagnosed, who are characterized by heterogeneity in their psychiatric diagnoses, their substance use patterns, and their current degree of dysfunction, presents a challenge. Several integrated treatment models have been developed that attempt to concurrently treat patients' psychiatric and substance abuse problems. At this point in the development of these "dual diagnosis" programs, treatment planning is hindered by a lack of knowledge about the relation of psychiatric severity to the process of recovery from alcohol abuse and dependence.^ The present study sought to advance the field's understanding of the relation between psychiatric severity and the process of behavior change through an examination of the relation between dimensions of psychiatric severity and Prochaska and DiClemente's Transtheoretical Model (TTM) constructs. The TTM, which focuses on identifying the processes of change that appear to underlie the modification of addictive behaviors, provides a way of conceptualizing and measuring specific elements relevant to the desired behavior change. Knowledge of the relation between these constructs and psychiatric severity will enable treatment planners to develop dual diagnosis programs which target clients' needs with a much higher level of specificity.^ One hundred-thirty two alcohol dependent patients in a dual diagnosis treatment program were assessed on psychiatric severity (defined as number of symptoms and level of distress resulting from symptoms) and the Transtheoretical Model constructs. The constructs include stages and processes of change for alcohol use, alcohol decisional balance, and alcohol abstinence self-efficacy. Results indicate that the TTM variable of "temptation to drink" is most strongly related to psychiatric severity: the more psychiatric distress a person is experiencing, the more he or she is tempted to drink. The "cons" of drinking were also related to psychiatric severity, indicating that participants who were experiencing more psychiatric distress also endorsed as important a higher number of the negative aspects of drinking.^ Additional aims of this investigation were to determine whether participants' scores on the Transtheoretical Model variables were associated with their: (a) severity of drinking, defined as frequency, quantity and consequences of use, (b) previous psychiatric and substance abuse treatment episodes, and (c) functional impairment. Associations were found among these variables and each of the key constructs of the Transtheoretical Model. Each association is explored in detail and implications for treatment programming are discussed. ^

Evaluation of androgenicity, abdominal adiposity, blood pressure and types of ovulatory patterns in a sample of women with menstrual irregularities

Objective: To determine the prevalence of and the relationships between the degree and source of hyperandrogenemia, ovulatory patterns and cardiovascular disease risk indicators (blood pressure, indices or amount of obesity and fat distribution) in women with menstrual irregularities seen at endocrinologists' clinic. Design: A cross-sectional study design. Participants: A sample of 159 women with menstrual irregularities, aged 15-44, seen at endocrinologists' clinic. Main Outcome Measures: androgen levels, body mass index (BMI), waist-hip ratio (WHR), systolic and diastolic blood pressure (SBP & DBP), source of androgens, ovulatory activity. Results: The prevalence of hyperandrogenemia was 54.7% in this study sample. As expected, women with acne or hirsutism had an odds ratio 12.5 (95%CI = 5.2-25.5) times and 36 (95%CI = 12.9-99.5) times more likely to have hyperandrogenemia than those without acne or hirsutism. The main findings of this study were the following: Hyperandrogenemic women were more likely to have oligomenorrheic cycles (OR = 3.8, 95%CI = 1.5-9.9), anovulatory cycles (OR = 6.6, 95%CI = 2.8-15.4), general obesity (BMI $\ge$ 27) (OR = 6.8, 95%CI = 2.2-27.2) and central obesity (WHR $\ge$ 127) (OR = 14.5, 95%CI = 6.1-38.7) than euandrogenemic women. Hyperandrogenemic women with non-suppressible androgens had a higher mean BMI (29.3 $\pm$ 8.9) than those with suppressible androgens (27.9 $\pm$ 7.9); the converse was true for abdominal adiposity (WHR). Hyperandrogenemic women had a 2.4 odds ratio (95%CI = 1.0-6.2) for an elevated SBP and a 2.7 odds ratio (95%CI = 0.8-8.8) for elevated DBP. When age differences were accounted for, this relationship was strengthened and further strengthened when sources of androgens were controlled. When the differences in BMI were controlled, the odds ratio for elevated SBP in hyperandrogenemic women increased to 8.8 (95%CI = 1.1-69.9). When the age, the source of androgens, the amount of obesity and the type of obesity were controlled, hyperandrogenemic women had 13.5 (95%CI = 1.1-158.9) odds ratio for elevated SBP. Conclusions: In this study population, the presence of menstrual irregularities are highly predictive for the presence of elevated androgens. Women with elevated androgens have a high risk for obesity, more specifically for central obesity. The androgenemic status is an independent predictor of blood pressure elevation. It is probable that in the general population, the presence of menstrual irregularities are predictive of hyperandrogenemia. There is a great need for a population study of the prevalence of hyperandrogenemia and for longitudinal studies in hyperandrogenemic women (adrenarche to menopause) to investigate the evolution of these relationships. ^

Left ventricular growth from age 8 to 18 and its anthropometric determinants: Longitudinal results from Project Heartbeat!

Left ventricular mass (LVM) is a strong predictor of cardiovascular disease (CVD) in adults. However, normal growth of LVM in healthy children is not well understood, and previous results on independent effects of body size and body fatness on LVM have been inconsistent. The purpose of this study was (1) to establish the normal growth curve of LVM from age 8 to age 18, and evaluate the determinants of change in LVM with age, and (2) to assess the independent effects of body size and body fatness on LVM.^ In Project HeartBeat!, 678 healthy children aged 8, 11 and 14 years at baseline were enrolled and examined at 4-monthly intervals for up to 4 years. A synthetic cohort with continuous observations from age 8 to 18 years was constructed. A total of 4608 LVM measurements was made from M-mode echocardiography. The multilevel linear model was used for analysis.^ Sex-specific trajectories of normal growth of LVM from age 8 to 18 was displayed. On average, LVM was 15 g higher in males than females. Average LVM increased linearly in males from 78 g at age 8 to 145 g at age 18. For females, the trajectory was curvilinear, nearly constant after age 14. No significant racial differences were found. After adjustment for the effects of body size and body fatness, average LVM decreased slightly from age 8 to 18, and sex differences in changes of LVM remained constant.^ The impact of body size on LVM was examined by adding to a basic LVM-sex-age model one of 9 body size indicators. The impact of body fatness was tested by further introducing into each of the 9 LVM models (with one or another of the body size indicators) one of 4 body fatness indicators, yielding 36 models with different body size and body fatness combinations. The results indicated that effects of body size on LVM can be distinguished between fat-free body mass and fat body mass, both being independent, positive predictors. The former is the stronger determinant. When a non-fat-free body size indicator is used as predictor, the estimated residual effect of body fatness on LVM becomes negative. ^

Patterns of alcohol and illicit substance use in the United States and Mexico. Substantive and methodologic issues in the cross-national analysis of alcohol and drug use data

This research examines prevalence of alcohol and illicit substance use in the United States and Mexico and associated socio-demographic characteristics. The sources of data for this study are public domain data from the U.S. National Household Survey of Drug Abuse, 1988 (n = 8814), and the Mexican National Survey of Addictions, 1988 (n = 12,579). In addition, this study discusses methodologic issues in cross-cultural and cross-national comparison of behavioral and epidemiologic data from population-based samples. The extent to which patterns of substance abuse vary among subgroups of the U.S. and Mexican populations is assessed, as well as the comparability and equivalence of measures of alcohol and drug use in these national samples.^ The prevalence of alcohol use was somewhat similar in the two countries for all three measures of use: lifetime, past year and past year heavy use, (85.0%, 68.1%, 39.6% and 72.6%, 47.7% and 45.8% for the U.S. and Mexico respectively). The use of illegal substances varied widely between countries, with U.S. respondents reporting significantly higher levels of use than their Mexican counterparts. For example, reported use of any illicit substance in lifetime and past year was 34.2%, 11.6 for the U.S., and 3.3% and 0.6% for Mexico. Despite these differences in prevalence, two demographic characteristics, gender and age, were important correlates of use in both countries. Men in both countries were more likely to report use of alcohol and illicit substances than women. Generally speaking, a greater proportion of respondents in both countries 18 years of age or older reported use of alcohol for all three measures than younger respondents; and a greater proportion of respondents between the ages of 18 and 34 years reported use of illicit substances during lifetime and past year than any other age group.^ Additional substantive research investigating population-based samples and at-risk subgroups is needed to understand the underlying mechanisms of these associations. Further development of cross-culturally meaningful survey methods is warranted to validate comparisons of substance use across countries and societies. ^

Cost-benefit analysis: The ``gold standard'' re-examined

The dissertation reviews the recommendations of the Panel on Cost Effectiveness in Health and Medicine (Panel) convened by the US Public Health Service in 1993 in four areas: aggregation of costs and benefits, methods of estimating resources used, definition of population impacted and perspective used in cost benefit analysis. Financial data from a clinical trial was used to test whether different approaches in each of the above four areas would change the net benefit resulting from a cost benefit analysis. Differences in aggregation of cost and benefit resulted in the same net benefit, but not the same cost/benefit ratios. Differences in resource use estimation methods, population subgroups definitions and perspectives all produced different net benefits. Difference in perspective resulted in different and often opposing decisions as to whether the proposed intervention from the clinical trial should be implemented. ^

Surveillance of antimicrobial resistance of Streptococcus pneumoniae and Haemophilus influenzae in children with pneumonia

In order to identify optimal therapy for children with bacterial pneumonia, Pakistan's ARI Program, in collaboration with the National Institute of Health (NIH), Islamabad, undertook a national surveillance of antimicrobial resistance in S. pneumoniae and H. influenzae. The project was carried out at selected urban and peripheral sites in 6 different regions of Pakistan, in 1991–92. Nasopharyngeal (NP) specimens and blood cultures were obtained from children with pneumonia diagnosed in the outpatient clinic of participating facilities. Organisms were isolated by local hospital laboratories and sent to NIH for confirmation, serotyping and antimicrobial susceptibility testing. Following were the aims of the study (i) to determine the antimicrobial resistance patterns of S. pneumoniae and H. influenzae in children aged 2–59 months; (ii) to determine the ability of selected laboratories to identify and effectively transport isolates of S. pneumoniae and H. influenzae cultured from nasopharyngeal and blood specimens; (iii) to validate the comparability of resistance patterns for nasopharyngeal and blood isolates of S. pneumoniae and H. influenzae from children with pneumonia; and (iv) to examine the effect of drug resistance and laboratory error on the cost of effectively treating children with ARI. ^ A total of 1293 children with ARI were included in the study: 969 (75%) from urban areas and 324 (25%) from rural parts of the country. Of 1293, there were 786 (61%) male and 507 (39%) female children. The resistance rate of S. pneumoniae to various antibiotics among the urban children with ARI was: TMP/SMX (62%); chloramphenicol (23%); penicillin (5%); tetracycline (16%); and ampicillin/amoxicillin (0%). The rates of resistance of H. influenzae were higher than S. pneumoniae: TMP/SMX (85%); chloramphenicol (62%); penicillin (59%); ampicillin/amoxicillin (46%); and tetracycline (100%). There were similar rates of resistance to each antimicrobial agent among isolates from the rural children. ^ Of a total 614 specimens that were tested for antimicrobial susceptibility, 432 (70.4%) were resistant to TMP/SMX and 93 (15.2%) were resistant to antimicrobial agents other than TMP/SMX viz. ampicillin/amoxicillin, chloramphenicol, penicillin, and tetracycline. ^ The sensitivity and positive predictive value of peripheral laboratories for H. influenzae were 99% and 65%, respectively. Similarly, the sensitivity and positive predictive value of peripheral laboratory tests compared to gold standard i.e. NIH laboratory, for S. pneumoniae were 99% and 54%, respectively. ^ The sensitivity and positive predictive value of nasopharyngeal specimens compared to blood cultures (gold standard), isolated by the peripheral laboratories, for H. influenzae were 88% and 11%, and for S. pneumoniae 92% and 39%, respectively. (Abstract shortened by UMI.)^