James B. Semmens

A decade of data linkage in Western Australia: strategic design, applications and benefits of the WA data linkage system

OBJECTIVES The report describes the strategic design, steps to full implementation and outcomes achieved by the Western Australian Data Linkage System (WADLS), instigated in 1995 to link up to 40 years of data from over 30 collections for an historical population of 3.7 million. Staged development has seen its expansion, initially from a linkage key to local health data sets, to encompass links to national and local health and welfare data sets, genealogical links and spatial references for mapping applications. APPLICATIONS The WADLS has supported over 400 studies with over 250 journal publications and 35 graduate research degrees. Applications have occurred in health services utilisation and outcomes, aetiologic research, disease surveillance and needs analysis, and in methodologic research. BENEFITS Longitudinal studies have become cheaper and more complete; deletion of duplicate records and correction of data artifacts have enhanced the quality of information assets; data linkage has conserved patient privacy; community machinery necessary for organised responses to health and social problems has been exercised; and the commercial return on research infrastructure investment has exceeded 1000%. Most importantly, there have been unbiased contributions to medical knowledge and identifiable advances in population health arising from the research.

Pregnancy after breast cancer: population based study.

Objectives To identify women who survived breast cancer and subsequently conceived and to determine the rate of pregnancy (proportion), management, outcome of the cancer, and outcome of the first subsequent pregnancy. Design Population based descriptive study with cases identified from the Western Australian data linkage system and validated by review of medical charts. Supplementary data obtained from hospital and clinician records. Setting Western Australia, 1982-2003. Participants Women aged <45 with a diagnosis of breast cancer who subsequently conceived. Main outcome measures Pregnancy outcome and rate, survival, time from diagnosis to pregnancy. Results Sixty two (54%) women with a diagnosis of breast cancer who subsequently conceived did so less than two years after their diagnosis: 29 of them had an abortion, 27 had a live birth, and six miscarried. Within a proportional hazards regression model subsequent pregnancy was associated with improved overall survival (hazard ratio 0.59, 95% confidence interval 0.37 to 0.95). When the model was stratified by time from diagnosis subsequent pregnancy was associated with improved overall survival in women who waited at least 24 months to conceive (0.48, 0.27 to 0.83) and a non-significant protective effect was seen for women who waited at least six months to become pregnant. Conclusions Our study does not support the current medical advice given to premenopausal women with a diagnosis of with breast cancer to wait two years before attempting to conceive. This recommendation may be valid for women who are receiving treatment or have systemic disease at diagnosis, but for women with localised disease early conception, six months after completing their treatment, is unlikely to reduce survival.

Fenestration in Endovascular Grafts for Aortic Aneurysm Repair: New Horizons for Preserving Blood Flow in Branch Vessels

PURPOSE To describe techniques for deploying fenestrated stent-grafts that use partial graft deployment and guided tracking of the fenestration to the arterial orifice. TECHNIQUE Fenestrations have been added to custom-made tube grafts and commercially manufactured Zenith stent-graft systems to preserve perfusion of aortic side branches. Partial device deployment, orientation markers on the endograft, and intraoperative angiography enable maneuvering of the fenestration over the orifice of the target vessel with the aid of guiding catheters. Placement of a Palmaz stent overlapping the fenestration and vessel orifice secures the junction. Two variations of fenestration have preserved blood flow in renal arteries during endovascular repair of abdominal aortic aneurysms (AAAs); similar techniques have maintained flow to the celiac axis in a thoracic aortic aneurysm. CONCLUSIONS Accurate placement of a fenestration over the orifice of a target vessel is feasible, but long-term maintenance of position is dependent on secure graft fixation. This capability brings us a step closer to overcoming the problem of inadequate necks in infra-renal AAAs, especially when the neck is foreshortened by asymmetry of the renal origins. It may also pave the way for the eventual replacement of the entire aorta with an endoluminal graft.

Outcomes of Fenestrated Endografts in the Treatment of Abdominal Aortic Aneurysm in Western Australia (1997-2004)

Purpose: To describe a 7-year experience with abdominal aortic aneurysm (AAA) repair using fenestrated Zenith endovascular endografts. Methods: Six endovascular surgeons from 7 medical centers in Perth, Western Australia, contributed data to this retrospective study of 58 AAA patients (51 men; mean age 75.5±8.5 years, range 60–94) treated with fenestrated endografts. Fenestrations were applied to 116 target vessels; more than half of patients had ≥2 target vessels. The results were based on satisfactory deployment of the stent-graft and fenestrations (technical success), technical success and no complications (procedural success), and aneurysm exclusion with no endoleak, rupture, unresolved complications, or dialysis (treatment success). Results: Technical success was 82.8% for patients (90.5% for target vessels), procedural success was 74.1%, and treatment success was 94.8%. There were no cases of conversion or rupture. The 30-day mortality rate was 3.4% (n=2). Over a mean follow-up of 1.4±1.2 years, 10 (17.2%) patients experienced loss of a target vessel (9.5% of target vessels). Factors associated with target vessel loss were no stent, >60° neck angulation, multiple renal vessels, and vessel diameter ≤4 mm. Four (6.9%) patients developed renal impairment, but none required dialysis. Fourteen (24.1%) patients had a secondary intervention. Unresolved endoleaks persisted in 1 (1.7%) patient. Conclusion: Fenestrated endografts extend the treatment options for infrarenal AAAs with necks unsuitable for standard endovascular repair. This early data show a trend toward higher mortality of selected patients with fenestrated endografts than for standard stent-graft repair, but the mortality rate is comparable to open repair. Target vessel occlusion predominantly results from pre-existing disease or the lack of a stent. The lessons learned from this experience contributed toward guidelines for users of fenestrated endografts.

Relationship of plasma HDL-Cholesterol to testosterone, estradiol, and sex-hormone-binding globulin levels in men and women

The significance of sex hormone levels in determining variation in high-density lipoprotein cholesterol (HDL-C) concentrations was studied in healthy Seventh Day Adventists (vegetarians) and Mormons. These groups were selected to avoid the confounding effects of alcohol consumption and cigarette smoking on HDL-C concentrations. Multivariate analysis showed that testosterone has a strong negative association with HDL-C in men (t = 3.99, P less than 0.001) and women (t = 2.04, P less than 0.05) when controlled for other variables including the concentration of sex-hormone-binding globulin (SHBG). Sex-hormone-binding globulin showed an independent positive association with HDL-C in men (P less than 0.001) and women (P less than 0.001). We postulate that the sex hormones affect HDL-C levels by regulating the activities of two important enzymes involved in the production and catabolism of HDL, namely, lipoprotein lipase and hepatic endothelial lipase. Other factors contributing independently to variation in HDL-C levels in this study were, in men, age and triglyceride, and in women, apoprotein-HDL, triglyceride, systolic blood pressure, heart rate, body mass index, and triceps skinfold thickness. Plasma estradiol concentrations were not significantly associated in either sex.

Long term relative survival after surgery for abdominal aortic aneurysm in Western Australia: population based study

Abstract Objective: To determine the long term relative survival of all patients who had surgery for abdominal aortic aneurysm in Western Australia during 1985-94. Design:Population based study. Setting:Western Australia. Subjects: All patients who had had surgery for abdominal aortic aneurysm in Western Australia during 1985-94. Main outcome measures: Morbidity and mortality data of patients admitted and surgically treated for abdominal aortic aneurysm in Western Australia during 1985-94. Elective, ruptured, and acute non-ruptured cases were analysed separately. Independent analyses for sex and patients aged 80 years or more were also undertaken. Postoperative (>30 days) relative survival was assessed against age and sex matched controls. Results: Overall, 1475 (1257 men, 218 women) cases were identified. The crude five year survival after elective surgery, including deaths within 30 days of surgery, was 79% for both men and women. When compared with a matched population the five year relative survival after elective surgery was 94.9% (95% confidence interval 89.9% to 99.9%) for men but only 88.0% (76.3% to 99.7%) for women. The five year relative survival of those aged 80 years and over was good: 116.6% (89.1% to 144.0%) compared with 92.4% (87.7% to 97.0%) for those under 80 years of age (men and women combined). Cardiovascular disease caused 57.8% of the 341 deaths after 30 days. Conclusion: In a condition such as abdominal aortic aneurysm, which occurs in elderly patients, relative survival is more clinically meaningful than crude survival. The five year relative survival in cases of elective and ruptured abdominal aortic aneurysm was better in men than in women. This is probably because of greater comorbidity in women with abdominal aortic aneurysm and this deserves more attention in the future. The long term survival outcome in octogenarians supports surgery in selected cases.

Analytical modeling and numerical simulation of forces in an endoluminal graft.

Purpose: To utilize mathematical analysis and computational fluid dynamics (CFD) to investigate the forces acting within the pressurized aorta and upon a stent-graft and how these forces may affect the ongoing performance of the stent-graft. Methods: Analytical force balance analysis and CFD simulations using the Fluent code were used to mimic blood flow through a bifurcated stent-graft in a person at rest. Steadystate blood flow was assumed in which the inlet pressure approximated the mean blood pressure (100 mm Hg) and the blood flow velocity was an approximation of the peak systolic flow rate (0.6 m/s). Two sizes of endoluminal grafts were analyzed: the larger graft had an inlet diameter of 3 cm and outlet diameters of 1 cm; the smaller graft diameters measured 2.4 cm proximally and 1.2 cm distally. The endografts were studied in 2 configurations: with the limbs straight and with one bent. Results: For the larger graft model, the normal peak blood flow induced a downward force of 7 to 9 N on the bifurcated grafts. Bending one of the limbs of the graft produced a sideways force of 1.3 N. For the smaller endograft, the downward force was in the range of 3.1 to 5.1 N and the sideways force on a curved limb was ∼1.5 N. The magnitude of the forces given by the analytical formulae and the CFD results agreed to within 2 significant figures. Conclusions: These results suggest that the downward force on a bifurcated stent-graft, which may exceed the force required to dislodge it when relying on radial attachment alone, is determined mostly by the proximal graft diameter. Curvature of the graft limbs creates an additional sideways force that works to displace the distal limbs of the graft from the iliac arteries.

Prostate cancer: socio-economic, geographical and private-health insurance effects on care and survival.

To examine the effects of demographic, geographical and socio‐economic factors, and the influence of private health insurance, on patterns of prostate cancer care and 3‐year survival in Western Australia (WA).

Falling rates of hospitalization and mortality from abdominal aortic aneurysms in Australia

BACKGROUND Studies of the population trends for abdominal aortic aneurysms (AAAs) in the period 1970 to 2000 all indicated that the incidence of AAAs was increasing. It is not known whether this increase has continued. We hypothesized that the incidence of AAAs has begun to fall in Australia. METHODS Age-standardized national trends in mortality from AAAs were estimated for the period 1999 to 2006, and hospital separations (deaths or discharges) for AAAs were estimated for the period 1999 to 2008. Poisson regression models were constructed to estimate the relative change over time. RESULTS The age-standardized mortality rate from AAAs fell by an average of 6.0% (95% confidence interval [CI], 4.7-7.3) per annum in men and 2.9% (95% CI, 1.0-4.7) in women. After adjusting for age, hospital separations for men decreased by an average of 2.3% (95% CI, 1.4-2.7) per annum for nonruptured AAAs, and 5.9% (95% CI, 5.0-6.6) for ruptured AAAs and for women decreased by an average of 2.2% (95% CI, 1.4-3.0) per annum for nonruptured AAAs, and 5.1% (95% CI, 3.7-6.5) for ruptured AAAs. Ruptured, compared with nonruptured, AAAs were proportionally more common in women compared with men. The age-specific trends in separations from hospital were all downward apart from nonruptured AAAs in individuals aged 80 years and over. CONCLUSIONS The rates of separation from hospital and mortality for AAAs in Australia have fallen since 1999. This suggests a true fall in incidence of AAAs. Although the reasons for this are unknown, it has implications for policy decisions about screening.

Trends in cataract surgery and postoperative endophthalmitis in Western Australia (1980−1998): the Endophthalmitis Population Study of Western Australia

Objectives: Postoperative endophthalmitis results from an intraocular infection and usually occurs following cataract surgery. It has significant morbidity and causes severe visual impairment or blindness of the eye. The aim of this study was to assess the trends in the incidence rates of cataract surgery and postoperative endophthalmitis in Western Australia for the period 1980−1998.