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Objectives: A computerised model of the Swedish two county trial of mammographic screening was built to explore the applicability of deterministic group modelling for health policy analysis and to examine trade offs between screening interval and population coverage on breast cancer mortality., Methods: Powersim system dynamics modelling software running on a PC was used. Model inputs were published data on the populations and screening regimens used in the trial, a Swedish female population life table, incidence of breast cancer in Sweden, 95% confidence intervals (95% CIs) for mean sojourn time and screening sensitivity, and survival after diagnosis., Results: The model's output--cumulative mortality from breast cancer--agreed closely with trial results. This was robust to uncertainties in key input variables. Furthermore, with hypothetical screening regimes that had a fixed total number of mammograms over a fixed period a positive association was found between more even distribution of mammograms among a population and reduction in breast cancer mortality. For example, screening 50% of a hypothetical population annually produced a 33% reduction in breast cancer mortality, whereas screening 100% of the population every 2 years produced a 48% reduction., Conclusions: Deterministic group simulation modelling can be used to build reliable, evidence based quantitative models for policy analysis. This opens health policy simulation modelling to epidemiological researchers and will assist them in identifying important information needs--such as breast cancer survival according to sojourn time (the time between cancer being detectable by screening and becoming symptomatic). Scenarios examining reductions in mortality for a given number of mammograms showed that the more equitable the distribution of screening mammograms, the greater the reduction in deaths from breast cancer.

The purpose of this study was to determine the iron status of preschool children in Sydney. We assessed 678 children aged 9 to 62 months living in 32 randomly selected census collection districts in central and southern Sydney for iron status using plasma ferritin; of these 678 children, 542 had zinc protoporphyrin tests, red cell indices and haemoglobin tests. Risk factors for iron deficiency were assessed by an administered questionnaire. Overall, the prevalence of iron depletion was 10.5 per cent, iron deficiency 2.8 per cent and iron deficiency anaemia 1.1 per cent. The 24-to-35-month age group (176 children) had the highest prevalence of iron deficiency anaemia of 3.0 per cent although iron depletion (18.7 per cent) and iron deficiency (5.4 per cent) were highest among the 9-to-23-month age group (182 children). Low iron status was related to age of under 24 months (odds ratio (OR) 2.86,95 per cent confidence interval (CI) 1.72 to 4.76). After adjustment for this age effect, the consumption of red meat fewer than four times a week was significantly associated with iron depletion (OR 2.27, CI 1.25 to 4.17) and there was a tendency for children who were being given a vitamin supplement to be less likely to be iron depleted (OR 4.00, CI 0.95 to 16.67). Iron deficiency and iron deficiency anaemia do not represent a major public health problem in preschool children in Sydney. However, for children in the age range of 12 to 36 months there is scope for interventions to further reduce the prevalence of iron deficiency anaemia.

A cross-sectional survey of 2044 Year I children enrolled in 24 primary schools was performed to determine the prevalence of tuberculosis (TB) infection. Of the 2044 children, 1458 (71 per cent) were Mantoux-tested and 1452 Mantoux reactions were read. Of the total, 6.5 per cent were Mantoux-positive; 17.8 per cent of overseas-born children and 2.8 per cent of Australian-born children were Mantoux-positive (relative risk for overseas-born 6.9, 95 per cent confidence interval 4.2 to 9.6). In the areas of Sydney where the study was conducted, there is a high prevalence of TB infection (non-contagious) among overseas-born children in the five- to seven-year age group. This indicates that there may be a large pool of infected children, a proportion of whom are at risk of developing active (contagious) adult-type TB in the future. These data, with other published data on TB infection rates in other age groups, can contribute to the estimation of the size of the infected pool in Australia to allow rational decisions regarding control of TB in Australia, including the possibility of introducing Mantoux screening and preventive therapy programs for high-risk groups.

1. The receptive fields and physiological properties of the sensitive cutaneous mechanoreceptive neurones in the leech Limnobdella australis were found to be very similar to those previously described in Hirudo medicinalis. 2. Following separation from the central nervous system (C.N.S.), the distal dendrite stump and cutaneous receptive field remained unchanged for at least 160 days. 3. There was little spreading of receptive fields into regions of skin isolated from the C.N.S. for at least 184 days. 4. Cutting one dendrite of a mechanoreceptive neurone which has two major dendrites produced little change in the receptive field of the intact dendrite. 5. Abnormalities were found in most of the receptive fields of operated leeches, irrespective of the site of operation. These abnormalities were not seen in normal leeches.

To measure the quality of vital status data in a retrospective cohort study of mortality among former servicemen of the Vietnam Conflict era, test subjects of independently determined vital status were included among study subjects during vital status ascertainment procedures. This allowed for differentiation between vital status "unknown" and incorrect assignment of vital status, and enabled measurement of the quality of both live and deceased vital status data. Four parameters based on sensitivity and specificity were used to express the quality of vital status data. The deceased specificity rate was 100 per cent, the deceased sensitivity rate was 95.7 per cent, the live specificity rate was 98.5 per cent, and the live sensitivity rate was 95.4 per cent. Using models of misclassification, the estimated death rate was found to be most sensitive to changes in the deceased specificity rate, indicating that emphasis should be given to minimizing incorrect ascertainment of truly alive subjects as deceased when developing vital status ascertainment procedures.