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G McDonald

Publications and source records attributed to G McDonald.

At least 19 recordsLinked to original sources
PubMed2003

Marker-assisted estimation of quantitative genetic parameters in rainbow trout, Oncorhynchus mykiss.

Estimation of quantitative genetic parameters conventionally requires known pedigree structure. However, several methods have recently been developed to circumvent this requirement by inferring relationship structure from molecular marker data. Here, two such marker-assisted methodologies were used and compared in an aquaculture population of rainbow trout (Oncorhynchus mykiss). Firstly a regression-based model employing estimates of pairwise relatedness was applied, and secondly a Markov Chain Monte Carlo (MCMC) procedure was employed to reconstruct full-sibships and hence an explicit pedigree. While both methods were effective in detecting significant components of genetic variance and covariance for size and spawning time traits, the regression model resulted in estimates that were quantitatively unreliable, having both significant bias and low precision. This result can be largely attributed to poor performance of the pairwise relatedness estimator. In contrast, genetic parameters estimated from the reconstructed pedigree showed close agreement with ideal values obtained from the true pedigree. Although not significantly biased, parameters based on the reconstructed pedigree were underestimated relative to ideal values. This was due to the complex structure of the true pedigree in which high numbers of half-sibling relationships resulted in inaccurate partitioning of full-sibships, and additional unrecognized relatedness between families.

Animals↗
PubMed2003

The potential contribution of the Queensland wet tropics region natural resource plan to river improvement and water quality.

This paper reports on work in progress on the new Wet Tropics Regional Natural Resource Management Plan and its potential to deliver river management and water quality outcomes. The plan is being prepared in accordance with the guidelines of the Nation Action Plan for Salinity and Water Quality/Natural Heritage Trust (NAP/NHT2). In particular the paper discusses the technical basis for priorities, target setting and implementation and the most effective instruments for achieving river improvement and water quality outcomes in the region.

Conservation of Natural Resources↗
PubMed2001

Prenatal diagnosis for women aged 37 years and over: to have or not to have.

Forty percent of pregnant women aged 37 years and over do not have prenatal diagnosis despite being eligible for a free test. The present study aimed to determine how often, and which, untested women were making a choice about this, how many declined an offer and why. A questionnaire was given to untested women, aged 37 years and over, at no less than 24 weeks gestation. A total of 375 (81.5%) women declined, 72 (16%) were not offered a test and 13 presented too late antenatally. There was a three-fold increased likelihood (OR 3.10 95% CI 1.44, 6.65) of no offer for urban non-English speaking background women, compared with the reference group (metropolitan, English speaking). Unpartnered women were also significantly less likely to receive an offer (OR 3.18, 95% CI 1.19, 8.46). Risk to the baby was the main reason for declining. When offered non-invasive prenatal screening, most decliners of prenatal diagnosis accepted, even those who declined because they were opposed to abortion. We estimate that overall 33% of older pregnant women were being offered and declining amniocentesis and/or chorion villus sampling (CVS). Only 6% were not offered a test, but this small proportion is over-represented by minority groups who must be given equal opportunity to make this choice.

Adult↗
PubMed2001

Risk factors for intermediate-term survival after coronary artery bypass grafting.

BACKGROUND: Risk factors for short-term mortality after coronary artery bypass grafting are well established, but little is known about risk factors for intermediate-term mortality. METHODS: We analyzed the outcomes of 11,815 patients undergoing coronary artery bypass grafting in one of the 43 cardiac surgery programs of the Department of Veteran Affairs. Risk factors for intermediate- and short-term mortality were determined using Cox proportional hazards regression models. Effects of risk factors during these two periods were explicitly compared. RESULTS: We found important differences in mortality risk-factor sets between the intermediate- and short-term periods after coronary artery bypass grafting. The majority of predictors of intermediate-term mortality were noncardiac-related variables, whereas the majority of predictors of short-term mortality were cardiac-related variables. Impaired functional status, chronic obstructive pulmonary disease, and renal dysfunction had greater effects in the intermediate-term period. Previous heart operation, angina class III or IV, previous myocardial infarction, and preoperative use of an intraaortic balloon pump had greater effects in the short-term period. CONCLUSIONS: The risk factors for intermediate-term mortality identified in this study can augment preoperative risk assessment and counseling of patients. Clinicians should be aware of the importance of noncardiac-related variables as predictors of mortality in the intermediate-term period after coronary artery bypass grafting.

Aged↗
PubMed2001

Comparison of surgical outcomes between teaching and nonteaching hospitals in the Department of Veterans Affairs.

OBJECTIVE: To determine whether the investment in postgraduate education and training places patients at risk for worse outcomes and higher costs than if medical and surgical care was delivered in nonteaching settings. SUMMARY BACKGROUND DATA: The Veterans Health Administration (VA) plays a major role in the training of medical students, residents, and fellows. METHODS: The database of the VA National Surgical Quality Improvement Program was analyzed for all major noncardiac operations performed during fiscal years 1997, 1998, and 1999. Teaching status of a hospital was determined on the basis of a background and structure questionnaire that was independently verified by a research fellow. Stepwise logistic regression was used to construct separate models predictive of 30-day mortality and morbidity for each of seven surgical specialties and eight operations. Based on these models, a severity index for each patient was calculated. Hierarchical logistic regression models were then created to examine the relationship between teaching versus nonteaching hospitals and 30-day postoperative mortality and morbidity, after adjusting for patient severity. RESULTS: Teaching hospitals performed 81% of the total surgical workload and 90% of the major surgery workload. In most specialties in teaching hospitals, the residents were the primary surgeons in more than 90% of the operations. Compared with nonteaching hospitals, the patient populations in teaching hospitals had a higher prevalence of risk factors, underwent more complex operations, and had longer operation times. Risk-adjusted mortality rates were not different between the teaching and nonteaching hospitals in the specialties and operations studied. The unadjusted complication rate was higher in teaching hospitals in six of seven specialties and four of eight operations. Risk adjustment did not eliminate completely these differences, probably reflecting the relatively poor predictive validity of some of the risk adjustment models for morbidity. Length of stay after major operations was not consistently different between teaching and nonteaching hospitals. CONCLUSION: Compared with nonteaching hospitals, teaching hospitals in the VA perform the majority of complex and high-risk major procedures, with comparable risk-adjusted 30-day mortality rates. Risk-adjusted 30-day morbidity rates in teaching hospitals are higher in some specialties and operations than in nonteaching hospitals. Although this may reflect the weak predictive validity of some of the risk adjustment models for morbidity, it may also represent suboptimal processes and structures of care that are unique to teaching hospitals. Despite good quality of care in teaching hospitals, as evidenced by the 30-day mortality data, efforts should be made to examine further the structures and processes of surgical care prevailing in these hospitals.

Education, Medical, Graduate↗
PubMed2001

A decade's experience with quality improvement in cardiac surgery using the Veterans Affairs and Society of Thoracic Surgeons national databases.

OBJECTIVE: To review the Department of Veteran Affairs (VA) and the Society of Thoracic Surgeons (STS) national databases over the past 10 years to evaluate their relative similarities and differences, to appraise their use as quality improvement tools, and to assess their potential to facilitate improvements in quality of cardiac surgical care. SUMMARY BACKGROUND DATA: The VA developed a mandatory risk-adjusted database in 1987 to monitor outcomes of cardiac surgery at all VA medical centers. In 1989 the STS developed a voluntary risk-adjusted database to help members assess quality and outcomes in their individual programs and to facilitate improvements in quality of care. METHODS: A short data form on every veteran operated on at each VA medical center is completed and transmitted electronically for analysis of unadjusted and risk-adjusted death and complications, as well as length of stay. Masked, confidential semiannual reports are then distributed to each program's clinical team and the associated administrator. These reports are also reviewed by a national quality oversight committee. Thus, VA data are used both locally for quality improvement and at the national level with quality surveillance. The STS dataset (217 core fields and 255 extended fields) is transmitted for each patient semiannually to the Duke Clinical Research Institute (DCRI) for warehousing, analysis, and distribution. Site-specific reports are produced with regional and national aggregate comparisons for unadjusted and adjusted surgical deaths and complications, as well as length of stay for coronary artery bypass grafting (CABG), valvular procedures, and valvular/CABG procedures. Both databases use the logistic regression modeling approach. Data for key processes of care are also captured in both databases. Research projects are frequently carried out using each database. RESULTS: More than 74,000 and 1.6 million cardiac surgical patients have been entered into the VA and STS databases, respectively. Risk factors that predict surgical death for CABG are very similar in the two databases, as are the odds ratios for most of the risk factors. One major difference is that the VA is 99% male, the STS 71% male. Both databases have shown a significant reduction in the risk-adjusted surgical death rate during the past decade despite the fact that patients have presented with an increased risk factor profile. The ratio of observed to expected deaths decreased from 1.05 to 0.9 for the VA and from 1.5 to 0.9 for the STS. CONCLUSION: It appears that the routine feedback of risk-adjusted data on local performance provided by these programs heightens awareness and leads to self-examination and self-assessment, which in turn improves quality and outcomes. This general quality improvement template should be considered for application in other settings beyond cardiac surgery.

Cardiac Surgical Procedures↗
PubMed2001

Severe juvenile chronic constipation.

Constipation in the paediatric population is common and encompasses a spectrum of organic and functional pathology which differ from that of the adult population. Recently an expert group published a comprehensive system of classification of childhood functional gastrointestinal disorders that may have useful clinical application. We present the case of an adolescent schoolgirl with severe constipation with extreme anorectal, urological and neurological sequelae who displayed inappropriate behavioral response to her condition. The patient appeared inappropriately unmotivated and undisturbed by the severity of her constipation. This abnormal psychological habituation and adaptation to an abnormal bowel habit perpetuated the constipation. In addition, we examined the role of recent advances in anorectal investigation techniques and treatment in the context of the recent guidelines issued by the American Gastroenterological Association

Adolescent↗
PubMed2000

Specialized intestinal metaplasia in patients with gastro-oesophageal reflux disease.

BACKGROUND: There is an increasing awareness that short (less than 3 cm) segments of Barrett's epithelium and macroscopically normal cardia epithelium may harbour specialized intestinal metaplasia (SIM), a premalignant phenotype. The prevalence of SIM was studied prospectively in an unselected population of patients attending for endoscopy, and the association of SIM with symptoms, lifestyle, medication, endoscopic oesophagitis and carditis was investigated. METHODS: Two hundred consecutive patients underwent endoscopy. Biopsies taken from just below the squamocolumnar junction were stained for SIM, and were analysed for carditis and Helicobacter pylori infection. A detailed questionnaire of symptoms, tobacco consumption and the use of proton pump inhibitors was completed. RESULTS: Forty-two patients (21 per cent) had SIM: 19 (15 per cent) of 126 in an endoscopically normal oesophagus, 15 (24 per cent) of 63 in a short segment of Barrett's epithelium and eight of 11 in classical Barrett's oesophagus. There was a significant association between SIM and carditis (P < 0.0001) and endoscopic oesophagitis (P = 0.03). CONCLUSION: SIM is prevalent in patients undergoing endoscopy, does not correlate with symptoms or H. pylori infection, but is significantly associated with endoscopic and pathological markers of gastro-oesophageal reflux.

Adolescent↗
PubMed2000

Specialized intestinal metaplasia: analysis of prevalence, risk factors and association with gastro-oesophageal reflux disease

AIMS: There is an increasing awareness that short (less than 3 cm) segments of Barrett's epithelium and macroscopically normal cardia epithelium may harbour specialized intestinal metaplasia (SIM), a premalignant phenotype. This was a prospective study of both the prevalence of SIM in an unselected population of patients attending for endoscopy, and the association of SIM with symptoms, lifestyle, medication, endoscopic oesophagitis and carditis. METHODS: Two hundred consecutive patients underwent endoscopy. Biopsies taken from just below the squamocolumnar junction were stained for SIM, and were analysed for carditis and Helicobacter pylori infection. A detailed questionnaire of symptoms, tobacco consumption and the use of proton pump inhibitors was completed. RESULTS: Forty-two patients (21 per cent) had SIM, 19 of 126 (15 per cent) in an endoscopically normal oesophagus, 15 of 63 (24 per cent) in a short segment of Barrett's epithelium and eight of 11 in classical Barrett's oesophagus. Comparative analysis between the SIM positive and negative groups with respect to potential risk factors is outlined below. Table 1. CONCLUSION: SIM is prevalent in patients undergoing endoscopy, does not correlate with symptoms or with H. pylori infection, but is significantly associated with endoscopic and pathological markers of gastro-oesophageal reflux.

Journal Article↗
PubMed2000

Public health implications of dengue in personnel returning from East Timor.

In north Queensland the vector of dengue fever (Aedes aegypti) is present; hence any viraemic individual importing dengue has the potential to transmit the disease locally. In early 2000 approximately 2,000 personnel returned from East Timor to Townsville, north Queensland. Seven importations of dengue occurred and individual cases were viraemic for up to 6 days in Townsville. No subsequent local transmission occurred. There were 3 cases each of dengue type 2 and dengue type 3. One case could not be serotyped. A response, including mosquito control measures, was initiated in another 18 cases in which dengue fever was clinically suspected but which subsequently proved not to be dengue. The planning and processes undertaken to prevent local transmission of dengue in Townsville during an intense period are described.

Dengue↗
PubMed1999

Relation of surgical volume to outcome in eight common operations: results from the VA National Surgical Quality Improvement Program.

OBJECTIVE: To examine, in the Veterans Health Administration (VHA), the relation between surgical volume and outcome in eight commonly performed operations of intermediate complexity. SUMMARY BACKGROUND DATA: In multihospital health care systems such as VHA, consideration is often given to closing low-volume surgical services, with the assumption that better surgical outcomes are achieved in hospitals with larger surgical volumes. Literature data to support this assumption in intermediate-complexity operations are either limited or controversial. METHODS: The VHA National Surgical Quality Improvement Program data on nonruptured abdominal aortic aneurysmectomy, vascular infrainguinal reconstruction, carotid endarterectomy (CEA), lung lobectomy/pneumonectomy, open and laparoscopic cholecystectomy, partial colectomy, and total hip arthroplasty were used. Pearson correlation, analysis of variance, mixed effects hierarchical logistic regression, and automatic interaction detection analysis were used to assess the association of annual procedure/specialty volume with risk-adjusted 30-day death (and stroke in CEA). RESULTS: Eight major surgical procedures (68,631 operations) were analyzed. No statistically significant associations between procedure or specialty volume and 30-day mortality rate (or 30-day stroke rate in CEA) were found. CONCLUSIONS: In VHA hospitals, the procedure and surgical specialty volume in eight prevalent operations of intermediate complexity are not associated with risk-adjusted 30-day mortality rate from these operations, or with the risk-adjusted 30-day stroke rate from CEA. Volume of surgery in these operations should not be used as a surrogate for quality of surgical care.

Adolescent↗
PubMed1999

Women's knowledge and attitudes about emergency contraception: a survey in a Melbourne women's health clinic.

The aim of the study was to determine the level of awareness of emergency contraception in women seeking pregnancy counselling and to investigate their attitudes towards emergency contraception. All women presenting for pregnancy counselling at a Melbourne women's health clinic in October 1997 were invited to complete a questionnaire detailing their contraceptive practices. One hundred and sixty-six questionnaires were distributed and 153 were completed (92% response rate). The majority of this sample population had heard of some form of emergency contraception and knew where to access it. However only 26% knew that emergency contraception should be taken within 72 hours of unprotected intercourse. Although 80% of the sample had heard of emergency contraception (or the morning after pill) only 9% used it in an attempt to prevent this pregnancy. The majority of the women surveyed support the increased availability of emergency contraception by rescheduling it to a non-prescription item and re-packaging as a single treatment.

Adolescent↗
PubMed1998

The Department of Veterans Affairs' NSQIP: the first national, validated, outcome-based, risk-adjusted, and peer-controlled program for the measurement and enhancement of the quality of surgical care. National VA Surgical Quality Improvement Program.

OBJECTIVE: To provide reliable risk-adjusted morbidity and mortality rates after major surgery to the 123 Veterans Affairs Medical Centers (VAMCs) performing major surgery, and to use risk-adjusted outcomes in the monitoring and improvement of the quality of surgical care to all veterans. SUMMARY BACKGROUND DATA: Outcome-based comparative measures of the quality of surgical care among surgical services and surgical subspecialties have been elusive. METHODS: This study included prospective assessment of presurgical risk factors, process of care during surgery, and outcomes 30 days after surgery on veterans undergoing major surgery in 123 medical centers; development of multivariable risk-adjustment models; identification of high and low outlier facilities by observed-to-expected outcome ratios; and generation of annual reports of comparative outcomes to all surgical services in the Veterans Health Administration (VHA). RESULTS: The National VA Surgical Quality Improvement Program (NSQIP) data base includes 417,944 major surgical procedures performed between October 1, 1991, and September 30, 1997. In FY97, 11 VAMCs were low outliers for risk-adjusted observed-to-expected mortality ratios; 13 VAMCs were high outliers for risk-adjusted observed-to-expected mortality ratios. Identification of high and low outliers by unadjusted mortality rates would have ascribed an outlier status incorrectly to 25 of 39 hospitals, an error rate of 64%. Since 1994, the 30-day mortality and morbidity rates for major surgery have fallen 9% and 30%, respectively. CONCLUSIONS: Reliable, valid information on patient presurgical risk factors, process of care during surgery, and 30-day morbidity and mortality rates is available for all major surgical procedures in the 123 VAMCs performing surgery in the VHA. With this information, the VHA has established the first prospective outcome-based program for comparative assessment and enhancement of the quality of surgical care among multiple institutions for several surgical subspecialties. Key features to the success of the NSQIP are the support of the surgeons who practice in the VHA, consistent clinical definitions and data collection by dedicated nurses, a uniform nationwide informatics system, and the support of VHA administration and managerial staff.

Hospitals, Veterans↗
PubMed1998

Magnetic resonance imaging of muscle in amyotrophic lateral sclerosis.

OBJECTIVE: To characterize leg muscle abnormalities in patients with ALS using MRI, and to correlate MRI with standard neurologic measures of motor neuron dysfunction. METHODS: Eleven ALS patients were studied twice (once at baseline and again after 4 months) and compared with eight normal control subjects. MRI data of the lower extremities were compared with tibialis anterior compound muscle action potential amplitude (CMAPa) and foot dorsiflexion maximal voluntary isometric contraction (MVIC). RESULTS: Muscle MRI was abnormal by visual inspection in six of 11 patients. The mean muscle T1 time and muscle volume were not different in patients compared with normal control subjects (p > 0.1). However, the mean T2 times were increased in the patients compared with normal control subjects (p = 0.009). T1 times did not correlate with CMAPa or MVIC. Muscle volume correlated with MVIC (r = 0.73 to 0.78, p < 0.02) but not with CMAPa (p > 0.05). There was a strong negative correlation (r < -0.8, p < or = 0.01) between muscle T2 time and MVIC and CMAPa. Also, the change in T2 relaxation time correlated with the change in CMAPa as the disease progressed (r = -0.63, p = 0.037). CONCLUSION: Of the MRI characteristics studied, T2 relaxation time was the best indicator of motor neuron dysfunction and may have a role in objective evaluation of motor neuron dysfunction.

Action Potentials↗
PubMed1997

Proteinase inhibitors from Nicotiana alata enhance plant resistance to insect pests.

The ornamental tobacco (Nicotiana alata) produces one 6-kDa chymotrypsin inhibitor and four 6-kDa trypsin inhibitors from a single 40.3-kDa precursor protein. Three different approaches have been used to assess the potential of these proteinase inhibitors (PIs) in insect control. The first was an in-vitro approach in which all five inhibitors, the single chymotrypsin inhibitor or three of the four trypsin inhibitors were tested for their ability to inhibit gut protease activity in insects from four orders. The second approach was to incorporate the N. alata PIs in the artificial diet of the native budworm (Helicoverpa punctigera) and the black field cricket (Teleogryllus commodus). H. punctigera larvae and T. commodus nymphs had a significant (P<0.01) reduction in growth after ingestion of the PI and were more lethargic than insects on the control diet. Several of the H. punctigera larvae also failed to complete moulting at the third or fourth instar. The third approach was to express the N. alata PIs in transgenic tobacco under the control of the 35S CaMV promoter. When H. punctigera larvae were fed tobacco leaves expressing the N. alata PIs at 0.2% soluble protein, significant (P<0.01) differences in mortality and/or growth rate were observed.

Journal Article↗
PubMed1997

Risk adjustment of the postoperative mortality rate for the comparative assessment of the quality of surgical care: results of the National Veterans Affairs Surgical Risk Study.

BACKGROUND: The National Veterans Affairs Surgical Risk Study was designed to collect reliable, valid data on patient risk and outcomes for major surgery in the Veterans Health Administration and to report comparative risk-adjusted postoperative mortality rates for surgical services in Veterans Health Administration. STUDY DESIGN: This cohort study was conducted in 44 Veterans Affairs Medical Centers. Included were 87,078 major noncardiac operations performed under general, spinal, or epidural anesthesia between October 1, 1991, and December 31, 1993. The main outcomes measure was all-cause mortality within 30 days after the index procedure. Multivariable logistic regression risk-adjustment models for all operations and for eight surgical subspecialties were developed. Risk-adjusted surgical mortality rates were expressed as observed-to-expected ratios and were compared with unadjusted 30-day postoperative mortality rates. RESULTS: Patient risk factors predictive of postoperative mortality included serum albumin level, American Society of Anesthesia class, emergency operation, and 31 additional preoperative variables. Considerable variability in unadjusted mortality rates for all operations was observed across the 44 hospitals (1.2-5.4%). After risk adjustment, observed-to-expected ratios ranged from 0.49 to 1.53. Rank order correlation of the hospitals by unadjusted and risk-adjusted mortality rates for all operations was 0.64. Ninety-three percent of the hospitals changed rank after risk adjustment, 50% by more than 5 and 25% by more than 10. CONCLUSIONS: The Department of Veterans Affairs has successfully implemented a system for the prospective collection and comparative reporting of risk-adjusted postoperative mortality rates after major noncardiac operations. Risk adjustment had an appreciable impact on the rank ordering of the hospitals and provided a means for monitoring and potentially improving the quality of surgical care.

Cohort Studies↗
PubMed1997

Risk adjustment of the postoperative morbidity rate for the comparative assessment of the quality of surgical care: results of the National Veterans Affairs Surgical Risk Study.

BACKGROUND: The National Veterans Affairs Surgical Risk Study was designed to collect reliable, valid data on patient risk and outcomes for major surgery in the Veterans Health Administration and to report comparative risk-adjusted postoperative mortality and morbidity rates for surgical services in the Veterans Health Administration. STUDY DESIGN: This was a cohort study conducted at 44 Veterans Affairs Medical Centers closely affiliated with university medical centers. Included were 87,078 major noncardiac operations performed under general, spinal, or epidural anesthesia between October 1, 1991, and December 31, 1993. The main outcomes measures in this report are 21 postoperative adverse events (morbidities) occurring within 30 days after the index procedure. Multivariable logistic regression risk-adjustment models for all operations and for eight surgical subspecialties were developed. RESULTS: Patient risk factors predictive of postoperative morbidity included serum albumin level, American Society of Anesthesia class, the complexity of the operation, and 17 other preoperative risk variables. Wide variation in the unadjusted rates of one or more postoperative morbidities for all operations was observed across the 44 hospitals (7.4-28.4%). Risk-adjusted observed-to-expected ratios ranged from 0.49 to 1.46. The Spearman rank order correlation between the ranking of the hospitals based on unadjusted morbidity rates and risk-adjusted observed-to-expected ratios for all operations was 0.87. There was little or no correlation between the rank order of the hospitals by risk-adjusted morbidity and risk-adjusted mortality. CONCLUSIONS: The Department of Veterans Affairs has successfully implemented a system for the prospective collection and comparative reporting of postoperative mortality and morbidity rates after major noncardiac operations. Risk adjustment had only a modest effect on the rank order of the hospitals.

Female↗