Biomedical subjects

C E Swanson

Publications and source records attributed to C E Swanson.

25 records · Page 2Linked to original sources

PubMed1990

Predicting the course of AIDS in Australia.

There have been urgent demands for knowledge about the epidemic of the acquired immunodeficiency syndrome (AIDS) in Australia. Accurate predictions are important for efficient allocation and planning of limited health-care resources. Ideal data for this purpose would be reliable knowledge of the past and present incidence of human immunodeficiency virus (HIV) infection. However, since the incidence of the infection is unknown predictions can only be based on historical data of the incidence of AIDS. In this article, we show the limitations of such predictions by examining a broad range of mathematical models that successfully track the observed data (1187 cases diagnosed to December 31, 1988). In addition, we describe a simple method for prediction in subgroups where the numbers of cases observed so far are small. Four models representing different forms of departure from the simple exponential model provide the best fits to the Australian AIDS data. Regional variability and a possible effect resulting from the introduction of zidovudine were incorporated into the models. Significant regional variability in the course of the epidemic was observed between New South Wales, Victoria and the rest of the country. For Australia as a whole, the doubling time changed from less than one year before mid 1987 to more than two years after this time. Model fits were improved by fitting the models to just the four years of data from 1985. The models give comparable predictions for the first year (1989) of around 600 new cases. However, by 1993 the predictions vary considerably, ranging from 500 to 2300 new cases. It is predicted that between 3100 and 6700 cases are likely to be diagnosed in Australia between 1989 and 1993. The results from the subgroup prediction demonstrate that when the observed number of cases is small, then the range of predictions for a future time interval is very wide. For reliable long-term predictions that are necessary for public health planning, basic information on the past and present incidence of HIV infection is urgently needed.

Acquired Immunodeficiency Syndrome↗

PubMed1990

Effect of zidovudine on survival of patients with AIDS in Australia.

Since the first case of AIDS in Australia was diagnosed in December 1982, there have been substantial improvements in the treatment of AIDS-related conditions. In particular, zidovudine was widely introduced into clinical practice in Australia in June 1987. In order to evaluate its effect, we compared the survival of patients diagnosed before and after July 31, 1987 using data available in early 1989. Survival distributions were compared by means of Kaplan-Meier curves and by fitting exponential survival models incorporating a special feature of the data. Before August 1, 1987 the overall distribution of survival times for patients with AIDS in Australia is well described by an exponential distribution with a mean of 1.04 years. The corresponding median survival time for this period was 8.8 months. For patients diagnosed with AIDS after July 31, 1987 the median survival time had not been attained by December 31, 1988. However, the estimated mean survival time increased to 2.7 years. Survival times were found to be remarkably stable over the different regions of Australia. We have shown that substantial improvements in survival of patients diagnosed with AIDS in Australia are associated with the widespread availability of zidovudine from mid 1987. To the best of our knowledge this study is the first of its kind to show a major shift in the distribution of survival associated with the introduction of antiviral therapy.

Acquired Immunodeficiency Syndrome↗

PubMed1990

Development of AIDS in a cohort of HIV-seropositive homosexual men in Australia.

The Sydney AIDS Prospective Study is a cohort study of 1057 homosexual men enrolled between February 1984 and January 1985. By June 30, 1989, 111 (26.8%) of the 414 men who were seropositive for antibodies to human immunodeficiency virus (HIV) at enrollment had developed the acquired immunodeficiency syndrome (AIDS). On univariate analysis the following baseline factors were significantly associated with subsequent development of AIDS: splenomegaly; a lymphocyte count less than 1500 x 10(6)/L; a percentage of CD4+ cells less than 20% of the total lymphocyte count; an absolute number of CD4+ cells less than 200 x 10(6)/L; and a CD4+: CD8+ ratio less than 1.00. In a proportional hazards model the following factors retained significance: a lymphocyte count less than 1500 x 10(6)/L; an absolute number of CD4+ cells less than 200 x 10(6)/L; and a CD4+: CD8+ ratio less than 1.00. A CD4+ cell count less than 200 x 10(6)/L carried the greatest relative risk (3.99) for the development of AIDS. This study has confirmed that the appreciable rates of progression to AIDS demonstrated in overseas cohorts of HIV-infected persons also apply in the Australian context. A number of laboratory variables was found to be predictive for the subsequent development of AIDS. As we were not able to determine accurately whether subjects were receiving antiretroviral treatment or prophylaxis for opportunistic infections the observed rates in this study should be seen as minimum estimates. These findings have important implications for HIV-infected persons and for public health planning, and emphasise the need for regular clinical monitoring and T-cell subset enumeration in HIV-infected persons.

Acquired Immunodeficiency Syndrome↗

PubMed1990

Factors influencing outcome of treatment with zidovudine of patients with AIDS in Australia. The Australian Zidovudine Study Group.

In a multicentre study of zidovudine therapy in Australia commencing in June 1987, 308 homosexual or bisexual men with AIDS started on zidovudine by 30 June 1988. Using follow-up data collected through 31 December 1988, the outcome of the first 18 months of zidovudine therapy in these patients has been analysed in terms of efficacy, expressed as survival and as time to development of a new AIDS-defining condition, and in terms of safety, expressed as toxicity. Median survival from time of diagnosis of AIDS was 124 weeks, significantly longer (P less than 0.001, logrank statistic) than the median survival of 44 weeks in historical controls representing AIDS patients prior to the availability of zidovudine therapy. Median survival time from starting zidovudine has not been reached in these patients, while 172 (56%) developed new AIDS-defining conditions, with median time to progression of 48 weeks. Anaemia requiring transfusion was experienced by 155 patients (50%). Significant differences (P less than 0.01, logrank statistic) in survival were found in favour of patients who commenced zidovudine therapy (Dx-zidovudine time) within 12 weeks of diagnosis and had baseline Karnofsky scores greater than or equal to 80, haemoglobin greater than or equal to 11 g/dl, CD4+ cell counts greater than or equal to 50 x 10(6)/l. Therapy-related significant differences (P less than 0.01, logrank statistic) in survival were found in favour of patients with no weight loss and who received the full zidovudine dose (1.2g) during the first 52 weeks of therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Acquired Immunodeficiency Syndrome↗

PubMed1990

Definition of two distinct types of AIDS-associated non-Hodgkin lymphoma.

Non-Hodgkin lymphoma (NHL) in a human immunodeficiency virus (HIV)-infected person is an AIDS-defining condition. There is both an increased incidence of NHL and a poorer prognosis for the disease in these HIV-infected persons, compared with patients who spontaneously develop NHL. A series of 41 consecutive patients with HIV-associated NHL treated at St Vincent's Hospital, Sydney, between 1984 and September 1989 was assessed. Of these, 36 had NHL proven on biopsy and NHL was diagnosed clinically in the other five. On histologic examination 11 had high-grade malignant lymphoma, small non-cleaved cell (SNCC) type, similar to Burkitt lymphoma, 18 had high-grade lymphoma large cell immunoblastic (LCI) type, and seven could not be classified due to inadequate material for assessment. The clinical features of these two groups were compared. Those patients with LCI had advanced CD4+ immunodeficiency and poor survival (median = 6 weeks). The other group with SNCC had better preserved immune function, and longer survival (median = 18 weeks). Three patients had survived longer than 3 years all of whom had SNCC lymphoma as their first AIDS-defining illness. The clinical features and prognostic factors demonstrated in this study document heterogeneity of NHL in HIV-infected patients and should be used as a guide to treatment of these patients, by reserving more intensive treatment for those persons with better prognostic features.

Acquired Immunodeficiency Syndrome↗

PubMed1989

Survival of patients with the acquired immunodeficiency syndrome in Australia.

The duration of survival of all persons with the acquired immunodeficiency syndrome (AIDS) in Australia who were diagnosed to July 31, 1987 was analysed by means of standard Kaplan-Meier methods in order to construct survival curves, and by log-rank tests which were used to assess the significance of differences among the curves. The median duration of survival was 10.4 months. Significant (P less than 0.001) differences in the survival curves were found between men and women (median survival, 11.4 and 3.8 months, respectively) by the log-rank test. Patients who were aged 20-49 years at diagnosis had a longer (P less than 0.001) median survival (11.4 months) than did those who were older than 60 years of age (2.7 months) and those who were aged less than 20 years (0.5 months) at diagnosis. Those patients who were infected by way of blood transfusions had a shorter (P less than 0.001) median survival (1.6 months) than did those who were infected through homosexual activity (11.4 months). Median survival time, which was stratified by the disease stage at presentation, varied from 12.4 months in those patients with Kaposi's sarcoma alone to 7.0 months in those patients with lymphoma (P = 0.01). The median survival time for those patients who presented solely with Kaposi's sarcoma was shorter than was that which has been reported from other developed countries. Multivariate analysis of all male cases by means of the proportional-hazards model indicated that the presentation of cases at an age that was greater than 50 years (relative risk, 2.36; 95% confidence interval [CI], 1.63-3.42) was associated independently with a reduced survival time, while the presentation of cases solely with Kaposi's sarcoma (relative risk, 0.67; 95% Cl, 0.49-0.92) was associated independently with an increased survival time. When all cases were included in this analysis, these same predictors of survival were significant; in addition, cases of AIDS as a result of the receipt of a blood transfusion were associated independently with a reduced survival time.

Acquired Immunodeficiency Syndrome↗

PubMedDate not supplied

Nutritional growth retardation is associated with defective lung growth in cystic fibrosis: a preventable determinant of progressive pulmonary dysfunction.

Evidence for a relationship between nutritional growth retardation in cystic fibrosis (CF) and progressive pulmonary dysfunction was evaluated by a prospective longitudinal study of changes in nutritional growth parameters, in relation to changes in pulmonary function data, in 61 moderately affected CF patients, aged 5-17 yr, during the equilibrated phase of lung growth. Age, sex, initial and serial weight and height Z scores, body cell mass (BCM) by total-body potassium (TBK) analysis, and changes in forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC), excluding data during pulmonary exacerbations, were analyzed by multiple regression analyses. The only significant predictor of change in FVC (best-fit model) was change in BCM, expressed as TBK (g/yr), TBK for age (percentage predicted), and TBK for height (percentage predicted) (p < 0.01). Standard anthropometric variables were not predictive. No reliable predictive model emerged for changes in FEV1. Relative decline in TBK for age was strongly predictive of decline in FVC (percentage predicted) accounting for 23% of this change. Patients with normal growth of the BCM had significantly less decline in FVC than those with retarded growth of the BCM (a fall of 2.5 vs. 6.8%/yr, p < 0.01). Impaired growth of the metabolically active BCM appears to be associated with progressive lung dysfunction in CF, possibly mediated by impaired lung growth. Achieving optimal nutrition and growth may minimize the progressive decline in pulmonary function commonly seen in this disease.

Adolescent↗