Blood lead levels among children aged 1 to 5 years in Wuxi City, China.

The objective of this study was to determine mean blood lead levels and prevalence of elevated blood lead levels among 1- to 5-year-old children in Wuxi City, China. By use of a representative cross-sectional survey that included measurements of capillary blood lead, 1117 children aged 1-5 years were examined from October through December, 1997. The geometric mean blood lead level for children 1-5 years of age in Wuxi City was 8.2 microg/dL (0.40 micromol/L); 27.3% had blood lead levels >or=10 microg/dL and 1.0% had blood lead levels >or=20 microg/dL. Blood lead levels were significantly higher for males and for those living in industrial areas, particularly the Beitang, Mashan, and Xinqu districts. Residence in these districts and in the Jiaoqu industrialized district also increased the likelihood of an elevated blood lead level, with odds ratios ranging from 2.59 to 4.53. In conclusion, blood lead levels among Wuxi City children are high enough to be of concern, particularly in industrial areas. Further studies are needed to better define the extent of lead exposure among children in China. In addition, national standards for blood lead collection and measurement methods should be applied in China.

Delta-aminolevulinic acid dehydratase genotype and lead toxicity: a HuGE review.

The ALAD gene (chromosome 9q34) codes for delta-aminolevulinic acid dehydratase (ALAD) (E.C. 4.2.1.24). ALAD catalyzes the second step of heme synthesis and is polymorphic. The ALAD G177C polymorphism yields two codominant alleles, ALAD-1 and ALAD-2, and it has been implicated in susceptibility to lead toxicity. Genotype frequencies vary by geography and race. The rarer ALAD-2 allele has been associated with high blood lead levels and has been thought to increase the risk of lead toxicity by generating a protein that binds lead more tightly than the ALAD-1 protein. Other evidence suggests that ALAD-2 may confer resistance to the harmful effects of lead by sequestering lead, making it unavailable for pathophysiologic participation. Recent studies have shown that individuals who are homozygous for the ALAD-1 allele have higher cortical bone lead levels; this implies that they may have a greater body lead burden and may be at higher risk of the long-term effects of lead. Individuals exposed to lead in occupational settings have been the most frequent subjects of study. Genotype selection bias may limit inferences from these studies. No firm evidence exists for an association between ALAD genotype and susceptibility to lead toxicity at background exposure levels; therefore, population testing for the ALAD polymorphism is not justified.

Use of geographic information system technology to aid Health Department decision making about childhood lead poisoning prevention activities.

The Centers for Disease Control and Prevention recommend that local public health agencies use local data to identify children at risk for lead exposure to ensure that they receive preventive services. The objective of this study was to demonstrate the usefulness of a geographic information system (GIS) in identifying children at risk for lead exposure. We conducted a descriptive study, using GIS technology, of the blood lead (BPb) levels and residential location of at-risk children screened for lead exposure. "At-risk children" were defined as those children living in housing built before 1950 or in an area with a high proportion of older housing. The study was conducted in Jefferson County, Kentucky, USA. Participants were the cohort of children born in 1995 and screened from 1996 through 1997, and children younger than age 7 years who were screened from 1994 through 1998. Outcome measures were the BPb level and residential location (address or target zone) of at-risk children screened from 1996 through 1997, and the number and location of homes where more than one child had been poisoned by lead from 1994 through 1998. The proportion of children screened who live within zones targeted for universal screening varied from 48% to 53%, while only 50% of the at-risk children in the entire county were screened. Between 1994 and 1998, 79 homes housed 35% of the 524 children with lead poisoning. These housing units were prioritized for lead-hazard remediation. Significant numbers of at-risk children throughout the county were not being tested for lead exposure, even in prioritized areas. GIS can be very useful to health departments in planning lead exposure screening strategies and measuring program performance.

Elevated blood lead levels and blood lead screening among US children aged one to five years: 1988-1994.

OBJECTIVES: To estimate the proportion of children 1 to 5 years of age who received blood lead testing during 1988-1994 and to assess whether predictors of testing coincided with predictors of elevated blood lead levels. DESIGN: Cross-sectional analysis of data from the Third National Health and Nutrition Examination Survey. Participants. US children 1 to 5 years of age. Outcome Measures. Prevalence of blood lead testing and elevated blood lead levels among children 1 to 5 years of age and odds ratios for factors predicting blood lead testing and elevated blood lead levels. RESULTS: Overall, 6.3% had elevated blood lead levels and 10.2% had undergone previous blood lead tests. Being of minority race/ethnicity, living in an older home, residing in the Northeast or Midwest regions of the United States, being on Medicaid, having a head of household with <12 years of education, and having a history of anemia were significant factors in both models. Additional independent risk factors for an elevated blood lead level included being sampled in phase 1 of the survey, being 1 to 2 years of age, not having a regular doctor, and being sampled during the summer months. Additional independent correlates of a previous blood lead test included having moved less than twice in one's lifetime, having a female head of household, and having parents whose home language was English. Of an estimated 564 000 children 1 to 5 years of age who had elevated blood lead levels and no previous screening test in 1993, 62% were receiving Medicaid, 40% lived in homes built before 1946, and 34% were black, non-Hispanic. CONCLUSIONS: Lead screening was more frequent among children with risk factors for lead exposure. However, among children with elevated blood lead levels, only one third had been tested previously. In 1993 an estimated 564 000 children 1 to 5 years of age had elevated blood lead levels but were never screened. Physicians should screen Medicaid-eligible children and should follow state or local health department recommendations about identifying and screening other at-risk children. In areas where no health department guidelines exist, physicians should screen all children or screen based on known risk factors.

Exposure of the U.S. population to lead, 1991-1994.

Blood lead measurements were obtained on 13,642 persons aged 1 year and older who participated in Phase 2 of the Third National Health and Nutrition Examination Survey (NHANES III) from 1991 through 1994. NHANES III is a national representative survey of the civilian, noninstitutionalized U.S. population. The overall mean blood lead level for the U.S. population aged 1 year and older was 2.3 microgram/dl, with 2.2% of the population having levels >=10 microgram/dl, the level of health concern for children. Among U.S. children aged 1-5 years, the mean blood lead level was 2.7 microgram/dl, and 890,000 of these children (4.4%) had elevated blood lead levels. Sociodemographic factors associated with higher blood lead levels in children were non-Hispanic black race/ethnicity, low income, and residence in older housing. The prevalence of elevated blood lead levels was 21.9% among non-Hispanic black children living in homes built before 1946 and 16.4% among children in low-income families who lived in homes built before 1946. Blood lead levels continue to decline in the U.S. population, but 890,000 children still have elevated levels. Public health efforts have been successful in removing lead from population-wide sources such as gasoline and lead-soldered food and drink cans, but new efforts must address the difficult problem of leaded paint, especially in older houses, as well as lead in dust and soil. Lead poisoning prevention programs should target high-risk persons, such as children who live in old homes, children of minority groups, and children living in families with low income.

The decline in US teen pregnancy rates, 1990-1995.

OBJECTIVES: Estimate pregnancy, abortion, and birth rates for 1990 to 1995 for all teens, sexually experienced teens, and sexually active teens. DESISN: Retrospective analysis of national data on pregnancies, abortions, and births. Participants. US women aged 15 to 19 years. OUTCOME MEASURES: Annual pregnancy, abortion, and birth rates for 1990 to 1995 for women aged 15 to 19 years, with and without adjustments for sexual experience (ever had intercourse), and sexual activity (had intercourse within last 3 months). RESULTS: Approximately 40% of women aged 15 to 19 years were sexually active in 1995. Teen pregnancy rates were constant from 1990 to 1991. From 1991 to 1995, the annual pregnancy rate for women aged 15 to 19 years decreased by 13% to 83.6 per 1000. The percentage of teen pregnancies that ended in induced abortions decreased yearly; thus, the abortion rate decreased more than the birth rate (21% vs 9%). From 1988 to 1995, the proportion of sexually experienced teens decreased nonsignificantly. CONCLUSIONS: After a 9% rise from 1985 to 1990, teen pregnancy rates reached a turning point in 1991 and are now declining. Physicians should counsel their adolescent patients about responsible sexual behavior, including abstinence and proper use of regular and emergency contraception.

Comparison of two question sequences for assessing pregnancy intentions.

Unintended pregnancies can have serious health, social, and economic consequences. Such pregnancies may be unwanted (a baby is not wanted at any time) or mistimed, yet wanted (a baby is wanted eventually). Intended pregnancies are those conceived when desired. Reproductive health survey respondents' understanding of these concepts and validity of survey results may be affected by question order and wording. Using a randomized crossover design, National Survey of Family Growth (NSFG) and Demographic and Health Survey (DHS) intendedness questions were asked in a 1993 survey of Arizona women aged 18-44 years. Of 2,352 ever-pregnant respondents, 25% gave discordant responses to DHS and NSFG questions about the most recent pregnancy. Age, marital status, household income, education, parity, time since pregnancy, and outcome of pregnancy were significantly predictive of discordant responses. DHS and NSFG questions yielded similar prevalence estimates of intendedness and wantedness; but young, unmarried respondents gave more "mistimed" responses on whichever question was asked later. Classifying pregnancies as intended, mistimed, or unwanted may be a problem for women who have not decided on lifetime reproductive preferences. Approaches to improving survey validity include addressing ambivalence, clarifying the definition of "unwanted," and, for young, unmarried women, not attempting to classify unintended pregnancies as mistimed or unwanted.

The use of condoms with other contraceptive methods among young men and women.

In a nationally representative sample of sexually experienced youths aged 14-22, 37% of young women and 52% of young men said the condom was the primary method used to prevent pregnancy at last intercourse; an additional 8% and 7%, respectively, said they used a condom at last intercourse; much of this represents dual use [corrected]. Condom use at last intercourse was reported by 25% of young men whose partner was using the pill. Significant independent predictors of condom use with the pill among men included younger age, black race, engaging in fewer nonsexual risk behaviors and having received instruction about HIV in school. Among young women, 21% of those relying on the pill reported also using a condom at last intercourse. For women, independent predictors of dual use included younger age, black race, older age at first sex, fewer nonsexual risk behaviors, having no partners in the previous three months and having talked to parents or other adult relatives about HIV.

PIP: The prevalence of combined use of condoms and non-barrier contraceptive methods for the purpose of dual protection against pregnancy and sexually transmitted diseases (STDs) was investigated in data from the 1992-93 US Youth Risk Behavior Survey. In this nationally representative sample of 4260 sexually active youth 14-22 years of age, 37% of females and 52% of males reported reliance on the condom at last intercourse as the primary method to prevent pregnancy. An additional 8% of females and 7% of males had used a condom for noncontraceptive purposes. Condom use at most recent intercourse was reported by 25% of males whose sexual partner was using oral contraceptives (OCs) and 21% of OC users. Black women had the highest and Hispanic women the lowest rate of dual condom/OC use. Other significant independent predictors of combined condom/OC use were--among males--younger age, engaging in fewer nonsexual risk behaviors (e.g., seatbelt non-use), and instruction about HIV in school and--among females--younger age, older age at first intercourse, fewer nonsexual risk behaviors, no sexual partners in the previous 3 months, and discussions with parents or other adults about HIV. These findings suggest that, for the majority of young people, the condom is primarily viewed as a means of preventing pregnancy and that prevention of HIV and other STDs is not a separate goal. Counseling and education should clearly define the efficacy of current methods of protection against STDs and pregnancy and clarify the distinct risk factors for these two outcomes.

Electron-beam CT: use of a calibration phantom to reduce variability in calcium quantitation.

PURPOSE: To measure scanner and patient variation in computed tomographic (CT) numbers for electron-beam CT and to determine the ability of calibration phantoms to reduce variability in calcium quantitation. MATERIALS AND METHODS: Two calibration phantoms were imaged to ensure longitudinal homogeneity and to determine the short-term intrascanner variation in CT numbers. Each phantom set was imaged twice a day for 14 weeks to determine intra- and interscanner variation. Data from examinations of 167 patients that included the phantom were analyzed to determine the intra- and interpatient variation in CT numbers of objects with known calcium concentrations. RESULTS: The calibration reduced scanner variations by approximately 25%. The calcium concentration associated with a CT number of 130 HU varied from 77.1 to 136.4 mg/cm3 and was dependent on patient girth, sex, smoking history, and image level. CONCLUSION: Scanner and patient variations in CT numbers in electron-beam CT can be reduced with a calibration phantom. In vitro and in vivo estimates of calcium concentration had a precision of 2% and 7%, respectively.

Quantification of coronary artery calcium by electron beam computed tomography for determination of severity of angiographic coronary artery disease in younger patients.

OBJECTIVES: This study attempted to 1) evaluate five quantitative measures of coronary artery calcium and determine which best agreed with coronary artery disease severity at angiography; and 2) determine optimal quantity cutpoints to distinguish among no, mild and significant disease. BACKGROUND: Coronary artery calcium identified noninvasively by electron beam computed tomography is a sensitive marker for atherosclerosis. Quantitative assessments of calcium could distinguish among patients with no, mild and significant disease in clinical, screening and research settings. METHODS: One hundred sixty patients, 23 to 59 years old, underwent coronary angiography and electron beam computed tomography. Coronary artery calcium was defined as dense (> 130 Hounsfield units) foci > or = 2 mm2 on the tomogram. Regression and receiver operating characteristic analyses were used to evaluate five quantitative measures of calcium as predictors of the largest stenosis in the coronary arteries and to identify optimal cutpoints for distinguishing among disease categories. No disease was defined as no stenosis, mild disease as 10% to 49% diameter stenosis in one or more major branches and significant disease as > or = 50% diameter stenosis in one or more major branches. RESULTS: All measures evaluated performed well. With calcific area as the quantitative measure, the best cutpoint for discriminating between patients with and without disease was the presence of calcium: sensitivity 81%, specificity 86% and overall accuracy 83%. The best cutpoint for discriminating between patients with and without significant disease was 18 mm2: sensitivity 86%, specificity 81% and accuracy 83%. CONCLUSIONS: Because the ranges of calcium quantity overlapped across disease categories, no cutpoints would distinguish among categories with absolute certainty. However, selected cutpoints could rule out disease in most healthy subjects and identify most patients with significant disease.

Quantity of coronary artery calcium detected by electron beam computed tomography in asymptomatic subjects and angiographically studied patients.

OBJECTIVE: To determine the prevalence and quantity of coronary artery calcium (CAC) in asymptomatic subjects from the general population, to identify asymptomatic subjects without risk factors for coronary artery disease (CAD) with CAC scores in the top quartile of the distribution, and to compare CAC scores in patients who underwent angiography with percentiles in asymptomatic subjects of the same age and sex. DESIGN: We studied two samples from Rochester, Minnesota, which consisted of 772 asymptomatic subjects from the general population and 145 patients who underwent angiography, all of whom were 20 to 59 years of age. METHODS: Asymptomatic subjects were classified on the basis of their CAD risk profile. All subjects in both study samples underwent electron beam computed tomography. Age- and sex-specific calcium score percentiles were calculated in the asymptomatic sample. RESULTS: CAC prevalence in the asymptomatic subjects was lower in female than in male subjects and increased with advancing age. Of the asymptomatic sample, 8% had a low-risk profile with calcium scores in the top quartile of the distribution. More patients than expected in the angiography sample had calcium scores above the 50th through 95th score percentiles. CONCLUSION: The quantity of CAC was substantially increased in patients who underwent angiography. Subjects with large amounts of CAC but without known CAD risk factors may be a valuable subset of the population to investigate for previously unidentified CAD risk factors.

Small lesions in the heart identified at electron beam CT: calcification or noise?

PURPOSE: To identify a minimum definition of coronary artery calcification (CAC) at electron beam computed tomography (CT) that would give repeatable results and be accurate as a marker for coronary artery disease. MATERIALS AND METHODS: Hyperattenuating (> 130 HU) foci 0.69-3.09 mm2 in area were evaluated for 256 subjects who underwent two sequential electron beam CT examinations to determine the percentage of hyperattenuating foci seen on a first examination that were seen again on a second examination. Accuracies of varying minimum definitions of CAC were determined in 160 subjects who underwent electron beam CT and coronary arteriography. RESULTS: Hyperattenuating foci more than 2 mm2 in area were seen again at a second examination in more than 50% of cases (P < .0001). At this minimum definition of CAC, the sensitivity and specificity for identifying any angiographically defined coronary artery disease were 82% and 85%, respectively. CONCLUSION: The 2-mm2-area definition of CAC was reliable and provided an accurate indication of coronary artery disease.

Detection of heart calcification with electron beam CT: interobserver and intraobserver reliability for scoring quantification.

PURPOSE: To assess interobserver and intraobserver reliability of three quantitative measures of coronary artery calcium burden: calcium "score," number of calcified lesions, and calcified area. MATERIALS AND METHODS: Electron beam computed tomographic (CT) scanning was used in a series of 25 patients to detect coronary artery calcification. Scan results were reviewed for quality by a radiologist, then scored by two radiologic technologists and by another radiologist. RESULTS: Many interobserver and intraobserver disagreements were noted on a lesion-by-lesion basis. Since most disagreements involved very small lesions, however, their impact was negligible for all three measures of calcium burden. CONCLUSION: It is not useful for more than one observer to independently score a single CT examination obtained to detect cardiac calcification, even when the arteries are heavily calcified.

Coronary artery calcification detected with ultrafast CT as an indication of coronary artery disease.

To assess the relationship of coronary artery calcification to angiographically detectable disease, the authors evaluated 100 patients less than 60 years of age who underwent clinically indicated coronary angiography and ultrafast computed tomography (CT). The ultrafast CT technique consisted of 3-mm-thick contiguous sections and a 100-msec acquisition time. All patients with clinically significant disease at angiography (defined as at least one stenosis with a diameter narrowing of at least 50%) had some coronary artery calcification present at ultrafast CT (100% sensitivity in this population). The absence of calcification at ultrafast CT had a 100% negative predictive value for clinically significant coronary artery disease. Specificity and positive predictive value were 47% and 62%, respectively. Sensitivity and specificity of ultrafast CT in the detection of patients with angiographically detectable disease were 94% and 72%, respectively. Ultrafast CT of the heart is an anatomically based, noninvasive test with high sensitivity for the detection of coronary artery calcification. Ultrafast CT may be beneficial in the screening of selected populations for the presence of atherosclerotic coronary disease.