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Biomedical subjects

A Rodgers

Publications and source records attributed to A Rodgers.

At least 73 records · Page 4Linked to original sources
PubMed1995

Systematic underestimation of treatment effects as a result of diagnostic test inaccuracy: implications for the interpretation and design of thromboprophylaxis trials.

Many clinical trials that have assessed strategies for the prevention of deep vein thrombosis have employed diagnostic tests that are less accurate than venography. The correct interpretation of these trials has been the subject of considerable debate. This paper attempts to quantify the likely effects of the use of inaccurate diagnostic tests (in particular fibrinogen scanning) on the validity and precision of estimates of treatment effects. It is shown that, if there is no difference in the rate of misclassification of deep vein thrombosis between study and control groups, then treatment effects will tend to be systematically underestimated in trials that only use inaccurate diagnostic tests. However, for trials in which there are no false positive diagnoses, such as those employing venography, the estimate of relative treatment effects will be unbiased. This phenomenon is demonstrated empirically by data from randomised trials of antiplatelet therapy. The implications of these findings are two-fold. First, so long as the accuracy of the test is the same in study and control groups, positive trial results cannot be ascribed to diagnostic test inaccuracy. Second, unbiased estimates of relative treatment effects can be obtained by using cheap, practicable and non-invasive screening tests that are supplemented by venographic assessment of positive test results. This would facilitate the conduct of much larger randomised trials than has generally been possible when mandatory venography was used; if future trials randomised some thousands of patients and employed confirmatory venography then they would provide both unbiased and precise estimates of relative treatment effects.

Clinical Trials as Topic↗
PubMed1994

Pharmacological thromboprophylaxis in hip and knee surgery: a survey of New Zealand orthopaedic surgeons.

A survey was conducted of the attitudes and practices of New Zealand orthopaedic surgeons on the use of pharmacological thromboprophylaxis (PT) for patients undergoing major hip or knee surgery. A questionnaire was sent to all 106 consultant surgeons known to perform hip or knee surgery and a response rate of 89% was obtained. The results suggested that while almost all surgeons used PT at some time, only about one-third of elective surgery patients and just a few per cent of patients with neck of femur fracture (NOFF) receive PT. For about three-quarters of surgeons, heparin (usually low molecular weight) was the most frequently used PT. About half of the surgeons began prophylaxis pre-operatively and about half stopped it when the patients were mobile postoperatively. Previous venous thromboembolism was felt by almost all surgeons to be a very important indication for PT; gross obesity, prolonged pre-operative immobility and active malignancy were thought to be very important factors by approximately one-half of the surgeons. The presence of a major bleeding diathesis or active peptic ulcer was cited as a contraindication to PT by more than two-thirds of all surgeons. Fear of bleeding complications and the rarity of thromboembolic complications were cited as reasons for limited use of PT by about one-third of surgeons. The results suggest that most surgeons usually rely on non-pharmacological methods of thromboprophylaxis, particularly for NOFF patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Arthroplasty↗
PubMed1994

Blood pressure, antihypertensive treatment and stroke risk.

ASSOCIATION BETWEEN BLOOD PRESSURE AND STROKE: Data from prospective observational studies indicate that usual levels of blood pressure are directly and continuously related to the risk of stroke. The strength of this association has been substantially underestimated by many previous analyses that have not taken account of the regression dilution bias; correction for this increases the strength of the association between blood pressure levels and stroke risk by about 60%. From corrected analyses it is apparent that a prolonged difference in usual systolic/diastolic blood pressure levels of just 9/5 mmHg would eventually confer about a one-third difference in stroke risk, with similar proportional effects in hypertensives and normotensives. RESULTS OF CLINICAL TRIALS: The results of randomized trials of antihypertensive drugs suggest that much or all of the long-term potential stroke avoidance associated with this level of prolonged blood pressure difference can be achieved within just a few years of beginning treatment. Overall, in 17 randomized trials of antihypertensive treatment, a net blood pressure reduction of 10-12 mmHg systolic and 5-6 mmHg diastolic conferred a reduction in stroke incidence of 38% (SD 4), with similar reductions in fatal and non-fatal strokes. Additionally, the sizes of the reductions were similar in trials in mild, moderate and more severe hypertension, in trials in older and younger patients and in trials in patients with a history of cerebrovascular disease and in patients without such a history. CONCLUSIONS: Because the proportional effects of treatment were similar in all these groups, the absolute effects of treatment on stroke varied in direct proportion to the background risk of stroke. Thus the greatest benefits were observed among those with a history of cerebrovascular disease, those above the age of 60 years and those with more severe hypertension.

Adult↗
PubMed1994

Urinary element concentrations in kidney stone formers and normal controls: the week-end effect.

Early morning urines were collected on each of three days (Monday-Wednesday) from 19 male stone-formers and 20 healthy male controls. Concentrations of 10 elements were determined using inductively coupled plasma atomic emission spectroscopy, graphite furnace atomic absorption spectroscopy and particle induced x-ray emission spectrometry. Data were treated using multivariate statistical methods. The results showed that the concentrations of several elements in the control urines were significantly raised on Mondays and that controls and stone formers differed with respect to certain elements, also on Mondays. The observed elevations were termed the "weekend effect". It is suggested that while stone-formers may regulate their diets throughout the entire week, normals may indulge in dietary excesses over the weekend. The weekend effect highlights the danger of placing too much emphasis on a single measurement of a urinary parameter and alerts investigators to take cognizance of the day on which urine collections are effected, especially when attempting to identify abnormal renal excretion patterns in stone-formers by comparison of their urinary variables with those of controls.

Humans↗
PubMed1993

The effects of blood pressure reduction in older patients: an overview of five randomized controlled trials in elderly hypertensives.

Direct evidence about the effects of antihypertensive treatment on vascular disease in older patients is available from five randomized trials conducted exclusively in patients over the age of 60 years. These trials involved a total of 12,483 individuals with systolic or diastolic hypertension (mean age = 72 years, mean entry blood pressure = 181/88 mmHg). Over an average follow-up period of 4.7 years, a 15/6 mmHg difference in blood pressure between study and control groups was achieved. Among those patients assigned active treatment, stroke incidence was reduced by 34% SD6 and coronary heart disease incidence was reduced by 19% SD7. These proportional reductions were of similar size to those observed in trials in predominantly younger patients. However, the absolute benefits observed in older patients were more than twice as great as those observed in younger patients. The results suggest that over 10 years, treatment would prevent at least one major vascular event among every 10 elderly patients at similar risk to those enrolled in the trials.

Aged↗
PubMed1992

Protection in simian immunodeficiency virus-vaccinated monkeys correlates with anti-HLA class I antibody response.

Our earlier reports demonstrated that Cynomolgus macaques vaccinated with either inactivated partially purified simian immunodeficiency virus (SIV), fixed SIV-infected C8166 (a human T lymphoblastoid cell line) cells, or fixed uninfected C8166 cells can be protected against a challenge infection with the 32H isolate of SIVmac 251 (grown in C8166) (Stott, E. J., W. L. Chan, K. H. G. Mills, M. Page, F. Taffs, M. Cranage, P. Greenway, and P. Kitchin. 1990. Lancet. 336:1538; Stott, E. J., P. A. Kitchin, M. Page, B. Flanagan, L. F. Taffs, W. L. Chan, K. H. G. Mills, P. Silvera, and A. Rodgers. 1991. Nature [Lond.]. 353:393). Protection is correlated with the levels of antibody response to cellular antigens in the human cells from which the virus immunogen was grown. However, the mechanism of protection is unclear. We report here the analysis of sera from these protected monkeys and demonstrate that there is positive correlation of protection with antibody response to the HLA class I molecule.

Animals↗
PubMed1991

Fluoride metabolism and fluoride content of stones from children with endemic vesical stones.

Twenty children with endemic vesical stones showed normal plasma and urinary excretion of fluoride on a mean fluoride intake of 2.5 +/- 0.8 mg/24 h. The mean fluoride content of the stones obtained from these children was 315.6 +/- 264.9 micrograms/g in the nucleus and 229.9 +/- 212.8 micrograms/g in the periphery (this was not statistically significant). Calcium-containing stones had a higher fluoride content than stones containing uric acid and ammonium urate. It was concluded that children with endemic vesical stones have normal fluoride metabolism. Trace quantities of fluoride present equally in the nucleus and peripheral parts of the stones suggest that fluoride does not cause initiation or growth of the nucleus of vesical stones and is adventitiously deposited with calcium salts in these stones.

Calcium Oxalate↗
PubMed1990

Pneumococcal C and type polysaccharide detection in the concentrated urine of patients with bacteremia.

The C polysaccharide of Streptococcus pneumoniae was detected in the concentrated urine of 23 of 33 patients with pneumococcal bacteremia using latex agglutination. Type-specific polysaccharides were detected in the urine of 17 of these 33 patients including 4 patients lacking C polysaccharide in their urine. These 4 with the 23 detected above gave a total sensitivity of 82% (27/33). The concentrated urine from an additional 11 patients with other bacteremias were tested by C polysaccharide and type-specific reagents and were negative. C polysaccharide detection in the concentrated urine of patients may be helpful in the diagnosis of pneumococcal infections.

Adolescent↗
PubMed1990

Empirical and clinical focus of child and adolescent psychotherapy research.

The present study evaluated the characteristics of research on child and adolescent psychotherapy. Published studies (N = 223) of psychotherapy from 1970 to 1988 were codified to characterize research, clinical, and methodological characteristics. The major results indicate that (a) treatment research focuses almost exclusively on the impact of treatment techniques with scant attention to influences (child/adolescent, parent, family, therapist) that may moderate outcome and (b) several characteristics of the children/adolescents and methods of treatment delivery and approaches depart markedly from those evident in the practice of treatment. Priorities for treatment research to place clinical practice on firmer empirical footing are discussed.

Adolescent↗
PubMed1990

Surfactant maturation and preterm premature membrane rupture: a case study.

Preterm premature membrane rupture (PPROM) is known to accelerate fetal lung surfactant maturation. The mechanism for this is unclear. We report a case of prolonged PPROM, where the maturation of fetal surfactant was studied in detail by the serial analysis of surfactant phospholipids in the drained liquor.

Adult↗
PubMed1988

Is diurnal variation in absorption of slow-release aminophylline an age-related phenomenon?

To specifically assess the possible influence of ageing on the changes in theophylline absorption, the plasma concentration-time profiles of sustained-release aminophylline were studied in 8 young and 8 elderly subjects after 9 a.m. and 9 p.m. administration. After 9 p.m. administration, in elderly subjects, maximum plasma theophylline concentrations (Cmax) were decreased, time to maximum concentration (tmax) was increased, and area under plasma concentration-time curve (AUC) was decreased compared to 9 a.m. dosing. This was true for single dose and at steady-state and suggests delayed and diminished absorption at night. No statistically significant changes were seen in the young subjects. This study therefore suggests that time related changes in absorption may be more significant in elderly subjects, possibly due to postural differences after 9 p.m. dosing, and this should be borne in mind when prescribing.

Adult↗