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Biomedical subjects

L Emmett

Publications and source records attributed to L Emmett.

At least 19 recordsLinked to original sources
PubMed2006

Modelling the effectiveness of chlamydia screening in England.

BACKGROUND: Several developed countries have initiated chlamydia screening programmes. Screening for a sexually transmitted infection has both direct individual and indirect population-wide effects. Mathematical models can incorporate these non-linear effects and estimate the likely impact of different screening programmes and identify areas where more data are needed. METHODS: A stochastic, individual based dynamic network model, parameterised from UK screening studies and data on sexual behaviour and chlamydia epidemiology, was used to investigate the likely impact of opportunistic screening on chlamydia prevalence. Three main strategies were considered for <25 year olds: (1) annual offer to women; (2) annual offer to women or if changed partner within last 6 months; (3) annual offer to men and women. Sensitivity analyses were performed for key screening parameters including uptake rate, targeted age range, percentage of partners notified, and screening interval. RESULTS: Under strategy 1, continuous opportunistic screening of women <25 years of age is expected to reduce the population prevalence by over 50% after 5 years. Prevalence is also expected to decrease in unscreened older women and in men. For all three strategies screening those aged over 25 results in small additional reductions in prevalence. Including men led to a faster and greater reduction in overall prevalence, but involved approximately twice as many tests as strategy 1 and 10% more than strategy 2. The frequency of attendance at healthcare sites limits the number of opportunities to screen and the effect of changing the screening interval. CONCLUSIONS: The model suggests that continuous opportunistic screening at high uptake rates could significantly reduced chlamydia prevalence within a few years. Opportunistic programmes depend on regular attendance at healthcare providers, but there is a lack of high quality data on patterns of attendance. Inequalities in coverage may result in a less efficient and less equitable outcome.

Adolescent↗
PubMed2002

A community study of health promotion in rural West Africa: details of a household survey and population census.

BACKGROUND: Hypertension is an important problem in sub-Saharan Africa. The low use of processed food in this area makes a population approach to reducing salt intake feasible. AIM: To create an age-sex register for 12 villages in Ghana as the first stage of a community study of the effect of dietary salt reduction on blood pressure and urinary sodium excretion in West African villagers. DESIGN: Household survey and population census. METHODS: Over three months, village maps were sketched and a complete list of total number of households, adults (with age and gender) and children in each village was obtained. RESULTS: The six semi-urban villages were larger than the six rural villages (10368 vs. 6597 inhabitants) and almost half the total population was under 16. CONCLUSIONS: Accurate census data are important in the design, implementation and interpretation of community studies and intervention trials. We outline the methods by which census data can be collected in rural and semi-urban sub-Saharan African villages, and emphasize the importance of painstaking, thorough work in the collection of such data.

Adolescent↗
PubMed2001

SPET of a computerised model of diffuse lung disease.

Emphysema is a common and debilitating disease that is the commonest cause of end-stage respiratory failure. Treatment is either by lung transplantation or by lung volume reduction surgery (LVRS) that improves the biomechanics of respiration. Patient selection for LVRS hinges on the demonstration of heterogeneous disease, predominantly involving the upper lobes, as a good surgical outcome is most likely in these patients. We used a virtual model of lung scintigraphy to compare planar with tomographic scintigraphy for the detection of diffuse lung disease. Lesions of the magnitude of the lung acinus, as well as larger and smaller lesions, were distributed throughout the lungs in volumes from 2% to 50%. Single-photon emission tomography does not add incremental value to planar images for the detection of diffuse lung disease.

Adult↗
PubMed2001

Acute and chronic rejection.

The major histocompatibility complex molecules are the primary antigens responsible for causing graft rejection, and T-cell recognition of alloantigens is the cardinal event initiating cellular rejection. Current concepts suggest that direct allorecognition mediates acute rejection, whereas indirect allorecognition mediates chronic rejection. In biopsy tissue of rejecting human renal allografts, several cytotoxic T-lymphocyte molecules are upregulated. The net result of cytokine release and the acquisition of cell surface receptors is the emergence of antigen-specific and graft-destructive T cells. Acute rejection is more frequent in children than in adults. By the end of the first year posttransplantation, 45% of living donor recipients and 60% of cadaver donor recipients will have an episode of rejection. In recent years, with improved immunosuppressive therapy, the incidence of acute rejection is decreasing at a rate of about 8% each year, however, chronic rejection graft loss has increased to 41% of all graft losses in the last 2 years. The mechanisms leading to chronic rejection and attempts to reduce acute rejections should provide a better half-life to children postrenal transplantation.

Acute Disease↗
PubMed2001

The 12th Annual Report of the North American Pediatric Renal Transplant Cooperative Study: renal transplantation from 1987 through 1998.

The North American Pediatric Renal Transplant Cooperative Study (NAPRTCS) presents an annual report for all transplants registered from January 1987 onwards. In this report we reviewed 6,534 renal transplants recorded for 5,958 patients who had entered the study by January 1999, and attempted to identify changes in practice patterns that had led to improved graft survival. There has been a steady decline in cadaver source transplants nationally and our accrual for 1996 and 1997 reflected this trend. There has also been a decrease in the number of infants and young children receiving a transplant in recent years. From a peak of 23.3% in the 1987-91 cohort, the current report shows that children under 6 yr of age now account for only 20.4% of all transplants. Changing disease patterns and rates of progression of disease have decreased the percentage of Caucasian children in the transplant registry, from 68.5% in the first 5 yr to 62.9% in the most recent cohort. Changing practice patterns have markedly reduced the use of cadaver donor (CD) kidneys (recovered from donors younger than 10 yr of age) from 35% in 1991 to 22% in the current report. Acute rejection patterns are identical for CD and living donor (LD) grafts for the first 2 weeks post-transplant. The comparative percentages on days 30 and 45 are 36% and 44% for CD, and 26% and 32% for LD recipients respectively. By the end of the first year post-transplant, 45% of LD and 60% CD recipients have had an acute rejection. There has been a marked improvement in our ability to reverse the initial episode of rejection; in 1987, 52% were completely reversed in LD recipients, and in 1997 61% were reversed. Rejection percentages continued to be lower in patients maintained on cyclosporin A (CsA) doses of > 6.4 mg/kg. One-, 3-, and 5-yr graft survival probabilities were 91%, 85%, and 80%, respectively, for LD recipients, and 83%, 73%, and 65% for CD recipients. Comparative 1- and 3-yr figures from 1987 to 1991 were 88% and 81% for LD and 74% and 63% for CD recipients. When short-term graft survival (1 yr) results were compared, a significant improvement was demonstrated from 71.7% in 1987/88 to 92.6% in 1998/1999 for CD transplants. Hence, changing practice patterns have gradually brought the short-term graft survival of CD transplants very close to that of LD transplants. The continuing decrease in the incidence of acute rejections in more recent years should translate into a further delay in the onset of chronic rejection, thus improving graft longevity.

Adolescent↗
PubMed2000

Continuing improvement in cadaver donor graft survival in North American children: the 1998 annual report of the North American Pediatric Renal Transplant Cooperative Study (NAPRTCS).

This report of the North American Pediatric Renal Transplant Cooperative Study (NAPRTCS) covers the years 1987-1997, and analyses data on 3,133 cadaver donor (CD) transplants performed in 2,736 patients. There has been a steady decline in the number of CD transplants in children since 1996. Kidneys recovered from donors under 10 years of age accounted for 35% of all transplants in 1987, whereas by 1996 they comprised less than 20%. Caucasian children received 54% of CD transplants, whereas African-American children received 21%. Children under 6 years of age received 17% of CD transplants. Approximately half (46%) of the patients were induced with a T-cell antibody, and at 7 years post-transplant triple therapy is used in 70% of those with a functioning graft. Cyclosporin A is the primary immunosuppressant, with 92% of the patients being maintained on it at 5 years post-transplant. Among patients receiving a transplant in 1997, 11% were initiated with another calcineurin inhibitor, tacrolimus. At 15 days post-transplant 20% of the patients have had a rejection episode and by day 45, 46% have had an acute rejection. The probability of developing a rejection within the first year was reduced from 71% in 1987-1988 to 47% in 1995-1996.

Adolescent↗
PubMed2000

A decade of living donor transplantation in North American children: the 1998 annual report of the North American Pediatric Renal Transplant Cooperative Study (NAPRTCS).

This report of the North American Pediatric Renal Transplant Cooperative Study (NAPRTCS) covers the years 1987-1997, and analyzes data on 2,904 living donor (LD) transplants performed in 2,779 patients. Since 1991, approximately 300 LD transplants have been performed each year at the participating centers of the NAPRTCS. Caucasian children account for 72% of all LD recipients while African-American children constitute only 11%. There has been a gradual decline in the number of transplants performed in children under the age of 6 years from a peak of 30% in 1987, to 21% in 1997. Preoperative calcineurin inhibitor therapy has dropped from 71% in 1987 to 38% in 1997. Through 1996, at six months post-transplant 97% of recipients were receiving prednisone, 88% were maintained on cyclosporin A, and 79% were receiving azathioprine. Of patients transplanted in 1997, 47% are maintained on mycophenolate and 10% are maintained on tacrolimus. By day 15, 20% of index transplant patients have had an acute rejection and by the end of the first year 47% have had a rejection episode. Among patients transplanted in 1995-1996, 40% had a rejection in the first year. Nine per cent of rejection episodes are irreversible in children under 2 years of age and 5% of the episodes are irreversible in 25-year-old children. Estimated graft survival probability at 1 year is 91%, at 3 years it is 84% and at 5 years it is 78.5%. Rejection accounts for 33% of graft loss and recurrence constitutes another 10%. Influential prognostic variables for graft survival are race (African-American vs. others, relative risk (RR) = 2.0, p < 0.001), > 5 random transfusions (RR = 1.6, p < 0.001, T cell induction therapy (RR = 0.78, p = 0.01), and later year of entry (1989-1990 vs. 1994-1995, RR = 0.95, p = 0.04). Patient survival at 1 and 3 years was 97% and 96.5%, respectively, however, the 3-year patient survival of children under 2 years was 89%. The mean height deficit baseline (n=2,677) was -1.86, at 1 year post-transplant (n=1,459) it was -1.80, and at 5 years post-transplant (n=592) it was -2,06. This report, devoted specifically to LD pediatric transplants, raises the issues regarding the use of immunosuppression such as preoperative calcineurin inhibitors and T-cell antibodies. Studies to address the high incidence of chronic rejection and recurrence of original disease are necessary. Additional areas of concern are the high infant mortality and continued growth retardation post-transplantation.

Adolescent↗
PubMed1999

Steady improvement in short-term graft survival of pediatric renal transplants: the NAPRTCS experience.

This report of pediatric renal transplantation covers the years 1987-1998. Since its inception in 1987, the NAPRTCS has collected data on 6,038 transplants performed in 5,516 patients provided by 73 renal centers across the country. FSGS, together with developmental lesions of dysplasia and obstructive uropathy, account for 40% of all transplants. There has been a steady increase in the use of LD donors among children with 54% of all transplants in 1996 and 1997 being live-related. About 72% of LD transplants are performed in Caucasian children, with African-American children unfortunately receiving a disproportionate percentage of CD kidneys. There has been a steady decline in the use of CD kidneys recovered from young individuals and a gradual decline in the number of transplants performed in young recipients (< 6 years old). Graft survival for LD recipients was 91%, 84% and 79% at one, 3 and 5 years, respectively, and the comparative figures for CD recipients were 81%, 72% and 64%, respectively. Acute and chronic rejections account for most of the graft losses, with chronic rejection accounting for more than 30%. There has been a steady improvement in one-year graft survival of CD recipients with the 1997-1998 cohort exhibiting an improvement of 16% over the 1987-1988 cohort. This improvement has been brought about by eliminating the use of infant donor kidneys, reducing the number of random transfusions and increasing the maintenance dose of cyclosporine. Posttransplant growth continues to be poor, with catch-up growth being exhibited only in children under age 6.

Adolescent↗
PubMed1997

Pediatric renal transplantation--the NAPRTCS experience.

The NAPRTCS has enrolled 4,329 children who have received an index renal transplant since 1987. Seventy-three percent of the transplant recipients were children above 6 years of age. In the age group below 6 years rejection episodes are not more frequent, however the first acute rejection episode is frequently irreversible leading to graft failure. Many of the renal disorders that lead to ESRD and transplantation in adults, such as diabetes and hypertension, are less often observed in the pediatric population. Developmental disorders, such as renal dysplasia and obstructive uropathy, are frequent diagnostic entities, and the most common glomerular disorder leading to transplantation in children is focal segmental glomerulosclerosis. In an attempt to overcome dialysis-associated growth retardation many pediatric renal centers resort to preemptive transplantation, thus 24% of the children receiving a transplant have never undergone dialysis. Graft survival in these children is similar to that observed in children receiving maintenance dialysis, however accelerated growth is not noted. Catch-up growth, defined as gain of 1 SDS, is observed in 47% of children below the age of 6 years and in only 22% of children over the age of 6 years. Infants (below 2 years) have a higher mortality rate following transplantation compared to older children. Long-term (5-year) graft survival for children receiving a cadaver donor graft is 60%, and for living donor kidney recipients the graft survival is 76%. Due to changes in practice patterns, such as a judicious use of cadaver donors, increased use of prophylactic T-cell antibody, and better maintenance immunosuppression, cadaver donor graft survival has improved each year since 1987. The cohorts of children with a cadaver donor transplant in the years 1991 and 1992 have a 2-year graft survival which is 10% better than that observed in the earlier years.

Adolescent↗