Population-based Prevalence Estimates Research Articles

Prevalence of cerebral palsy: Autism and Developmental Disabilities Monitoring Network, three sites, United States, 2004

Background Cerebral palsy (CP) is the most common cause of motor disability in children and an important public health issue in the United States. The Autism and Developmental Disabilities Monitoring (ADDM) Network is a multisite program funded by the Centers for Disease Control and Prevention to determine trends in the prevalence of children with developmental disabilities, including CP, in the United States. This report describes population-based estimates of CP prevalence among 8-year-old children in three sites in the United States. Methods The ADDM Network conducted surveillance of CP among 8-year-old children living in north central Alabama, metropolitan Atlanta, and south central Wisconsin in 2004 (N = 68,272). This multisite collaboration involved the retrospective collection, linking, and analysis of data from multiple service providers and the population census estimates. Results The average prevalence of CP in 2004 across the three sites was 3.3 per 1,000 (95% confidence interval, 2.9−3.8). The prevalence was significantly higher in boys than in girls overall (male/female ratio, 1.4:1). The most common subtype across all three sites was spastic CP, ranging from 85% in Georgia to 89% in Alabama and Wisconsin. Conclusions Ongoing, systematic, population-based surveillance in different areas of the United States is needed to describe and monitor CP prevalence. In addition, enhancing the surveillance system to include information about functional abilities is needed to better understand the public health impact of CP and strategies for improving quality of life and participation in activities at home and in the community.

Prevalence of Asthma in a General Population Cohort of Farm Children: Comparison of Estimates Based on Parental Report and Medical Record Review

ABSTRACT Methods of ascertaining and defining asthma in epidemiologic research vary, and the extent of agreement between such measures is not clearly understood. Within a broader investigation of early-life farm exposures and risk of childhood asthma and other atopic conditions, the authors sought to generate and compare population-based estimates of asthma prevalence among farm children using several definitions, based on both parental report and medical chart review. The Marshfield Epidemiologic Study Area (MESA) is a geographically defined, population-based cohort that receives nearly all health care from Marshfield Clinic and affiliated institutions. The region includes about 2200 farms, and over 9500 children aged 5 to 17 years who were born in the region served as the study population. A stratified random sample of 1000 overselecting for likely farm resident children was drawn. Parents of 553 children completed the survey and gave permission to review medical records. Informative records were available for 531 (96%). A weighted analysis provided estimates for the full study population. Asthma ascertainment included parental reports of past asthma diagnosis, history of wheezing, and asthma medication use, as well as documentation of asthma diagnoses and medication use in the medical chart. Prevalence of asthma among farm children using a broad composite definition was 24.8%. Prevalence based on parental reports of a specific asthma diagnosis was 11.2%, whereas medical chart documentation of a past asthma diagnosis was found for 10.1% of farm children. Seventy-one percent of parental reports were validated in the charts, and 80% of chart-confirmed diagnoses were reported by the parent. Basing asthma prevalence for farm children on a history of asthma medication use gave a higher estimate than did history of a diagnosis. Of farm children, 19.2% reported wheezing or respiratory whistling, with 8.1% occurring in the past year. Observational research on asthma can be substantially influenced by ascertainment methods and case definitions. Although prevalence estimates based on a past asthma diagnosis were quantitatively similar for parental reports and chart confirmation, agreement on specific cases between the two sources was less than expected. Care should be taken to clearly describe asthma case definitions when reporting results of observational asthma research.

Sexual risk behaviours and HIV seroprevalence among male sex workers who have sex with men and non-sex workers in Campinas, Brazil

Objectives:To compare population-based prevalence estimates of sexual risk behaviours and HIV seroprevalence of male sex workers who have sex with men (MSM) and those not engaged in sex work in...

Prevalence in the United States of selected candidate gene variants: Third National Health and Nutrition Examination Survey, 1991-1994.

Population-based allele frequencies and genotype prevalence are important for measuring the contribution of genetic variation to human disease susceptibility, progression, and outcomes. Population-based prevalence estimates also provide the basis for epidemiologic studies of gene–disease associations, for estimating population attributable risk, and for informing health policy and clinical and public health practice. However, such prevalence estimates for genotypes important to public health remain undetermined for the major racial and ethnic groups in the US population. DNA was collected from 7,159 participants aged 12 years or older in Phase 2 (1991–1994) of the Third National Health and Nutrition Examination Survey (NHANES III). Certain age and minority groups were oversampled in this weighted, population-based US survey. Estimates of allele frequency and genotype prevalence for 90 variants in 50 genes chosen for their potential public health significance were calculated by age, sex, and race/ethnicity among non-Hispanic whites, non-Hispanic blacks, and Mexican Americans. These nationally representative data on allele frequency and genotype prevalence provide a valuable resource for future epidemiologic studies in public health in the United States.

Bayesian melding for estimating uncertainty in national HIV prevalence estimates

Objective:To construct confidence intervals for HIV prevalence in countries with generalised epidemics.Methods:In the Bayesian melding approach, a sample of country-specific epidemic curves describing HIV prevalence over time is derived based...

Prevalence of HNF1A (MODY3) mutations in a Norwegian population (the HUNT2 Study)

Previous reports have indicated that maturity-onset diabetes of the young (MODY) caused by hepatocyte nuclear factor 1A (HNF1A) mutations (MODY3) is the most common MODY subtype in Northern Europe, but population-based prevalence estimates are lacking. We sought to determine the prevalence of HNF1A-MODY in diabetic subjects of a defined Norwegian population (the HUNT2 Study). Of the 1972 diabetic HUNT2 subjects, we identified a subgroup of 43 suspected MODY cases based on information on family history, disease onset and anti-glutamic acid decarboxylase autoantibody status. These cases were considered a discovery group for HNF1A mutations and underwent full DNA sequencing. Subsequently, the entire cohort of diabetic HUNT2 subjects was screened for three selected HNF1A mutations. Possible founder effects were examined using the Norwegian MODY Registry. Three subjects from the discovery group harboured HNF1A mutations. Two subjects had the previously described R229Q mutation, one had a novel S6N alteration, whereas the HNF1A hot-spot mutation P291fsinsC was not identified. Genotyping the cohort of diabetic HUNT2 subjects identified five additional R229Q-positive subjects. Microsatellite analysis performed for all R229Q-positive probands of the Norwegian MODY Registry and those found in the HUNT2 population revealed that 17 of 18 (94%) had genotypes consistent with a common haplotype. Clinical MODY criteria were fulfilled in 2.2% of diabetic HUNT2 subjects. The minimum prevalence of HNF1A-MODY among diabetic HUNT2 subjects was 0.4%. Because of founder effects, registry-based prevalence studies probably need to be very large and they should also include prospectively collected phenotypes and extensive mutation screening to establish the true prevalence of MODY.

Prevalence of Cognitive Impairment without Dementia in the United States

Cognitive impairment without dementia is associated with increased risk for disability, increased health care costs, and progression to dementia. There are no population-based prevalence estimates of this condition in the United States. To estimate the prevalence of cognitive impairment without dementia in the United States and determine longitudinal cognitive and mortality outcomes. Longitudinal study from July 2001 to March 2005. In-home assessment for cognitive impairment. Participants in ADAMS (Aging, Demographics, and Memory Study) who were age 71 years or older drawn from the nationally representative HRS (Health and Retirement Study). Of 1770 selected individuals, 856 completed initial assessment, and of 241 selected individuals, 180 completed 16- to 18-month follow-up assessment. Assessments, including neuropsychological testing, neurologic examination, and clinical and medical history, were used to assign a diagnosis of normal cognition, cognitive impairment without dementia, or dementia. National prevalence rates were estimated by using a population-weighted sample. In 2002, an estimated 5.4 million people (22.2%) in the United States age 71 years or older had cognitive impairment without dementia. Prominent subtypes included prodromal Alzheimer disease (8.2%) and cerebrovascular disease (5.7%). Among participants who completed follow-up assessments, 11.7% with cognitive impairment without dementia progressed to dementia annually, whereas those with subtypes of prodromal Alzheimer disease and stroke progressed at annual rates of 17% to 20%. The annual death rate was 8% among those with cognitive impairment without dementia and almost 15% among those with cognitive impairment due to medical conditions. Only 56% of the nondeceased target sample completed the initial assessment. Population sampling weights were derived to adjust for at least some of the potential bias due to nonresponse and attrition. Cognitive impairment without dementia is more prevalent in the United States than dementia, and its subtypes vary in prevalence and outcomes.

Population and antenatal-based HIV prevalence estimates in a high contracepting female population in rural South Africa

BackgroundTo present and compare population-based and antenatal-care (ANC) sentinel surveillance HIV prevalence estimates among women in a rural South African population where both provision of ANC services and family planning is prevalent and fertility is declining. With a need, in such settings, to understand how to appropriately adjust ANC sentinel surveillance estimates to represent HIV prevalence in general populations, and with evidence of possible biases inherent to both surveillance systems, we explore differences between the two systems. There is particular emphasis on unrepresentative selection of ANC clinics and unrepresentative testing in the population.MethodsHIV sero-prevalence amongst blood samples collected from women consenting to test during the 2005 annual longitudinal population-based serological survey was compared to anonymous unlinked HIV sero-prevalence amongst women attending antenatal care (ANC) first visits in six clinics (January to May 2005). Both surveillance systems were conducted as part of the Africa Centre Demographic Information System.ResultsPopulation-based HIV prevalence estimates for all women (25.2%) and pregnant women (23.7%) were significantly lower than that for ANC attendees (37.7%). A large proportion of women attending urban or peri-urban clinics would be predicted to be resident within rural areas. Although overall estimates remained significantly different, presenting and standardising estimates by age and location (clinic for ANC-based estimates and individual-residence for population-based estimates) made some group-specific estimates from the two surveillance systems more predictive of one another.ConclusionIt is likely that where ANC coverage and contraceptive use is widespread and fertility is low, population-based surveillance under-estimates HIV prevalence due to unrepresentative testing by age, residence and also probably by HIV status, and that ANC sentinel surveillance over-estimates prevalence due to selection bias in terms of age of sexual debut and contraceptive use. The results presented highlight the importance of accounting for unrepresentative testing, particularly by individual residence and age, through system design and statistical analyses.

Clinical risk factors for fracture in postmenopausal Canadian women: A population-based prevalence study

Clinical risk factor assessment can be used to enhance fracture risk estimation based upon bone densitometry alone. Population- and age-specific risk factor prevalence data are required for the construction of these risk models. Our objective was to derive population-based prevalence estimates of specific clinical risk factors for postmenopausal women resident in the Province of Manitoba, Canada. A random sample of 40,300 women age 50 or older identified from the provincial health plan was mailed a validated self-report risk factor survey. The response rate was 8747 (21.7%) with a final study population of 8027 women after exclusions. The individual prevalence for each clinical risk factor ranged from 5.8% for hyperthyroidism to 33.0% for a fall in the preceding 12 months. Most point prevalence estimates were similar to other large cohort studies, though the prevalences of inactivity and poor mobility were higher than expected while height at age 25 and the prevalence of any fracture after age 50 were lower than expected. Most of the respondents (86.9%) had at least one non-age clinical risk factor, 60.6% had two or more, and 33.5% had three or more. Age affected risk factor prevalence, and older age was associated with a higher rate of multiple risk factors. The availability of age-specific risk factor prevalence rates in this population may allow for more accurate fracture risk modeling.

Global burden of COPD: systematic review and meta-analysis

The aim of this study was to quantify the global prevalence of chronic obstructive pulmonary disease (COPD) by means of a systematic review and random effects meta-analysis. PubMed was searched for population-based prevalence estimates published during the period 1990-2004. Articles were included if they: 1) provided total population or sex-specific estimates for COPD, chronic bronchitis and/or emphysema; and 2) gave method details sufficiently clearly to establish the sampling strategy, approach to diagnosis and diagnostic criteria. Of 67 accepted articles, 62 unique entries yielded 101 overall prevalence estimates from 28 different counties. The pooled prevalence of COPD was 7.6% from 37 studies, of chronic bronchitis alone (38 studies) was 6.4% and of emphysema alone (eight studies) was 1.8%. The pooled prevalence from 26 spirometric estimates was 8.9%. The most common spirometric definitions used were those of the Global Initiative for Chronic Obstructive Lung Disease (13 estimates). There was significant heterogeneity, which was incompletely explained by subgroup analysis (e.g. age and smoking status). The prevalence of physiologically defined chronic obstructive pulmonary disease in adults aged > or =40 yrs is approximately 9-10%. There are important regional gaps, and methodological differences hinder interpretation of the available data. The efforts of the Global Initiative for Chronic Obstructive Lung Disease and similar groups should help to standardise chronic obstructive pulmonary disease prevalence measurement.

Improved National Prevalence Estimates for 18 Selected Major Birth Defects--United States, 1999-2001

Continuing efforts are needed to improve surveillance for birth defects, which are the leading cause of infant mortality in the United States. Although state and local surveillance data indicate that approximately 3% of births are affected by any of 45 birth defects, no national estimates based on population-based birth defects surveillance have been available for specific types of birth defects other than neural tube defects (spina bifida and anencephaly). This report describes estimates of national prevalence and number of affected births in the United States each year during 1999-2001 for 18 selected major birth defects. The findings indicated that 10 of the 18 defects affected more than 1,000 infants each year in the United States. The conditions with the highest prevalence included orofacial clefts, which affect approximately 6,800 infants annually, and Down syndrome, which affects approximately 5,500 infants annually. Population-based national prevalence estimates of birth defects can help determine resource needs for basic and public health research and assist in planning for the health-care and educational needs of the U.S. population.

The Prevalence of Trichomoniasis in Young Adults in the United States

The prevalence of trichomoniasis in the general population of the United States is unknown. This study provides the first population-based prevalence estimates of trichomoniasis among young adults in the United States. The National Longitudinal Study of Adolescent Health (Add Health) is an ongoing prospective cohort study. In a cross-sectional analysis of Wave III of Add Health (N = 12,449), we determined the prevalence of trichomoniasis using a polymerase chain reaction assay. The estimated overall prevalence of trichomoniasis in U.S. young adults was 2.3% (95% confidence interval [CI], 1.8-2.7%). The prevalence was slightly higher among women (2.8%; 95% CI, 2.2-3.6%) than men (1.7%; 95% CI, 1.3-2.2%). The prevalence increased with age and varied by region, with the south having the highest prevalence (2.8%; 95% CI, 2.2-3.5%). The prevalence was highest among black women (10.5%; 95% CI, 8.3-13.3%) and lowest among white women (1.1%; 95% CI, 0.8-1.6%). Among men, the prevalence was highest among Native Americans (4.1%; 95% CI, 0.4-29.3%) and blacks (3.3%; 95% CI, 2.2-4.9%), and lowest among white men (1.3%; 95% CI, 0.9-1.8%). Trichomoniasis is moderately prevalent among the general U.S. population of young adults and disturbingly high among certain racial/ethnic groups.

Hepatitis C Virus Infection, Linxian, China1

Bloodborne viruses may have spread in rural China during the past 25 years, but population-based prevalence estimates are lacking. We examined the frequency of hepatitis C virus (HCV) and HIV type 1 (HIV-1) among residents of Linxian, a rural community in Henan Province. In 2000, blood was collected from participants (> or = 55 years of age) who had enrolled in a population-based nutritional intervention trial in 1985. We randomly selected 500 participants for HCV testing and 200 participants for HIV-1 testing. For HCV, 48 (9.6%) of 500 participants were positive by enzyme immunoassay and recombinant immunoblot assay (95% confidence interval, 7.0%-12.2%), and prevalence was lowest in the most geographically isolated participants. Among the HCV-infected participants, 42 had a specimen available from 1985, of which 16 (38.1%) were positive for HCV. For HIV-1, 0/200 participants were positive. We conclude that HCV is now a common infection among older adults in Linxian, China.

Epidemiologie des beruflich bedingten Handekzems

Occupational skin diseases constitute about 30% of all occupational diseases worldwide and also in Germany. Thereby, occupational skin diseases take the leading position of all occupational diseases. About 90% of occupational skin diseases are eczemas which are usually located on the hands. According to estimates of the registers for occupational skin diseases in Northern Bavaria and the Saarland, Germany, which have been effective since 1990 and 1999, the incidence of occupational skin diseases is 6.7 and 6.8 per 10,000 full-time workers and year. Other incidence estimates from Western industrialized countries range between 5 and 19 cases per 10.000 full-time workers and year. Population-based estimates for a 1-year prevalence of hand dermatitis, which rely on an assessment by questionnaire, range between 6.7% in Germany and 8.9% in Norway. Studies, which included a skin examination for outcome assessment, e.g. revealed a point prevalence of 0.5% for cases which should be seen by a physician in a sample of 20,749 US citizens or a 1-year prevalence of 10.6% for a sample of 16,587 subjects from Sweden. According to a cross-sectional study from Denmark, school children in the age of 12 - 16 years exhibited hand eczema in 3.2% at the time of investigation and reported a 1-year prevalence of 7.3%. For the latter, the predominance of female gender was confirmed (10.1% vs. 4.6%). Epidemiological studies on occupational hand dermatitis are for several methodological reasons hardly comparable. This is due to different sample sizes and selection criteria, the use of different measures of frequency and outcome assessment including the fact that no generally accepted and validated diagnostic criteria exist. Population-based as well as studies in different occupational groups revealed a higher prevalence in women. Larger studies in food- and metal-processing industries as well as in hairdressing apprentices showed a marked increase in eczema prevalence during the 3-year period of apprenticeship. For example, prevalence of hand dermatitis increased in apprentices of food industry from East-Thuringia from 17.5% to 27.5%, in hairdressing apprentices from Northwest Germany from 12.9% to 23.9% and in apprentices of metal industry from 0 to 23%, i.e. from 8.6% to 14.1%. The latter study was performed in apprentices of the car industry and allowed to distinguish the increase in hand eczema between metalworkers (9,2% to 15.3%), blue-collar workers (8.8% to 14.1%), and white-collar workers (4.6% to 6.9%). The Prevention of Occupational Skin Disease in Hairdressers Study (POSH) clearly demonstrated that the prevalence estimates largly depend on the chosen outcome definition. For various definitions of hand eczema the prevalence at the end of apprenticeship varied between 2.7% and 23.9%. A high 3-year prevalence of 20.7% was also observed in German office workers and an expected high 1-year prevalence of 46% was reported for female cleaners from Denmark. The overall high and during apprenticeship further increasing prevalence of occupational hand dermatitis calls for intense and specific measures of prevention.

Hepatitis C virus infection in the general population: A community-based study in West Bengal, India

Limited information is available about the prevalence and genotype distribution of hepatitis C virus (HCV) in the general population of India. A community-based epidemiologic study was carried out in a district in West Bengal, India. By a 1:3 sampling method, 3,579 individuals were preselected from 10,737 inhabitants of 9 villages of the district, of whom 2,973 (83.1%) agreed to participate. Twenty-six subjects (0.87%) were HCV antibody positive. The prevalence increased from 0.31% in subjects <10 years of age to 1.85% in those ≥60 years. No difference in prevalence between men and women was observed. Serum alanine aminotransferase (ALT) levels were elevated in 30.8% (8 of 26) of anti-HCV-positive subjects compared with 3.2% (94 of 2,947) anti-HCV-negative subjects ( P < .001). HCV RNA was detectable in 80.8% (95% CI, 65.6%-95.91%) of the anti-HCV-positive subjects by reverse transcription-primed polymerase chain reaction (RT-PCR). The participants were HCV types 1b in 2 (9.5%), 3a in 8 (38.1%), 3b in 6 (28.6%), and unclassified in 5 (23.8%). Nucleotide sequencing and phylogenetic analysis assigned the unclassified type to genotype 3e. In conclusion, this study provides general population-based estimates of HCV prevalence, including genotypes, from a South Asian country. Although the prevalence of HCV infection in this population was lower than that reported from industrialized countries of the west, the total reservoir of infection is significant and calls for public health measures, including health education to limit the magnitude of the problem.(H epatology 2003;37:802-809.)

Multistate analysis of factors associated with intimate partner violence

Background: Reports on prevalence estimates and risk factors of intimate partner violence (IPV) are limited in that they (1) focus on specific subgroup populations that are not representative of all women or (2) involve long questionnaires that are not useful as surveillance tools. Objectives: To report prevalence estimates and identify demographic and lifestyle factors associated with IPV in a large population-based sample of U.S. women using surveillance data. Methods: Behavioral Risk Factor Surveillance System (BRFSS) data from eight U.S. states were analyzed individually and as a pooled sample (N=18,415). Multivariate logistic regression models were used to examine associations between IPV and the factors of interest. Results: Factors consistently associated with IPV across the majority of states and in the pooled analysis included young age (pooled adjusted odds ratio [aOR], 3.07), single marital status (pooled aOR, 2.89), divorced/separated marital status (pooled aOR, 4.67), and annual household income <$25,000 (pooled aOR, 1.89). In addition, lack of health insurance, receipt of Medicaid, cigarette smoking, presence of children in the home, self-reported fair/poor health, and frequent mental distress were associated with IPV after adjustment for covariates. Conclusions: This study provides population-based estimates of IPV prevalence and factors associated with IPV using surveillance data. By pooling BRFSS data from individual states, the resulting large sample has adequate power to detect significant associations and has increased precision in the estimates of IPV risk. In addition, this study identifies high-risk populations to target for education and intervention programs and demonstrates the need for improved IPV surveillance.

Mental health services for youths in foster care and disabled youths.

This study assessed whether mental health services for youths differ with respect to medical assistance aid category. Computerized claims for 15,507 youths with Medicaid insurance in a populous county of a mid-Atlantic state were used to establish population-based prevalence estimates of mental disorders and psychotherapeutic treatments during 1996. An analysis of service claims revealed that the prevalence of mental disorders among youths enrolled in foster care (57%) was twice that of youths receiving Supplemental Security Income (SSI; 26%) and nearly 15 times that of other youths receiving other types of aid (4%). Rates of mental health service use were pronounced among foster care youths aged 6 to 14 years. Attention deficit/hyperactivity disorder, depression, and developmental disorders were the most prevalent disorders. Stimulants, antidepressants, and anticonvulsants were the most prevalent medications. Youths enrolled in foster care and youths receiving SSI use far more mental health services than do youths in other aid categories. Additional research should evaluate the complexity and outcomes of mental health services for youths in foster care.

Subgroup-specific effects of questionnaire wording on population-based estimates of mammography prevalence

This study investigated whether an apparent downturn in prevalence rates of mammography use reported in the 1992 Behavioral Risk Factor Surveillance System (BRFSS) questionnaire resulted from a change in questionnaire wording. In a pretest-posttest design (1990-1991 vs 1992), piecewise linear regression analyses were based on monthly prevalence estimates of mammography use among female BRFSS respondents 40 years or older. Self-reported mammography use was lower by 3.5 percentage points (95% confidence interval [CI] = 1.5, 5.5) overall--and lower by 13.6 percentage points (95% CI = 2.6, 24.6) among Black women with less than a high school education--when predicted from 1992 data than when predicted from 1990-1991 data. A change in questionnaire wording in the BRFSS caused demographic-specific effects in population-based estimates of mammography use.

The prevalence of CMA/CMPI in young children: the validity of parentally perceived reactions in a population-based study.

The present study aimed to estimate the prevalence of adverse reactions to milk, as population-based prevalence estimates based on objective diagnostic procedures are rare. Children with parentally reported reactions to milk were selected for further examination from a population-based cohort of 2721 children. At the age of 2(1/2) years, they underwent a stepwise diagnostic procedure that included diet trials at home, skin prick tests, and open and double-blind, placebo-controlled food challenges. A sample of children with symptoms not attributed to milk was selected for assessment of unrecognized reactions. The estimated point prevalence of cow's milk allergy and cow's milk protein intolerance (CMA/CMPI) in children with parentally perceived reactions at the age of 2(1/2) years was estimated to be 1.1% (CI 0.8-1.6). However, this was an underestimate, as unrecognized reactions were detected. Most reactions were not IgE-mediated. The positive predictive value of a parentally perceived reaction depended on the number of times it had been reported and was good for reactions reported three times (at 12, 18, and 24 months of age). The present study confirms previous findings that parents overestimate milk as a cause of symptoms in their children; however, it also indicates that unrecognized reactions may be a problem as well.

The prevalence of allergy to egg: a population-based study in young children.

The aim of the present study was to estimate the prevalence of adverse reactions to egg, as population-based prevalence estimates based on objective diagnostic procedures are lacking. The parents of 2721 children in a population-based birth cohort completed questionnaires on the occurrence of any reaction to food at 12, 18, and 24 months of age. Children with parentally reported reactions to eggs at the age of 2 years were selected for further examination. A stepwise diagnostic procedure was developed that included diet trials at home, skin prick tests, and open and double-blind, placebo-controlled food challenges. The mean age of the children at the time of the examination was 2.5 years (CI 2.5-2.6). A sample of children without perceived reactions to egg was also selected for assessment of unrecognized reactions. The estimated point prevalence of allergy to egg in children aged 2(1/2) years was 1.6% (CI 1.3-2.0%), with an upper estimate of the cumulative incidence by this age calculated roughly at 2.6% (CI 1.6-3.6). Almost all reactions were IgE mediated. In general, two-thirds of the parentally perceived reactions were verified. However, the positive predictive value of a parentally perceived reaction depended on the number of times it had been reported, and increased from 50% to 100%, for reactions reported one and three times, respectively. Unrecognized reactions were infrequent. This study confirms that allergy to egg is frequent in a child population.