Biomedical subjects

J D Dawson

Publications and source records attributed to J D Dawson.

At least 37 records · Page 2Linked to original sources

PubMed1998

Predictors of neonatal resuscitation, low Apgar scores, and umbilical artery pH among growth-restricted neonates.

OBJECTIVE: To identify risk factors associated with poorer immediate neonatal outcomes among growth-restricted neonates. METHODS: Records of all 530 growth-restricted neonates born between January 1989 and February 1995 were reviewed. Outcomes included resuscitation measures, Apgar scores, and umbilical blood gas values. Neonates were assigned to one of six anesthetic groups, and outcomes were compared. Predictors of poorer outcomes were examined using logistic and linear regression. RESULTS: Neonates exposed to general anesthesia were more likely to be intubated (37.9% versus 4.1%, P < .001, Pearson chi2) and had lower mean 1- (4.0 versus 7.0) and 5-minute (6.5 versus 8.4) Apgar scores (P < .01, Scheffé) than those in all other anesthetic groups. They also had significantly lower umbilical artery (UA) pH values than neonates who received nalbuphine, epidural, or no anesthesia (7.21 versus 7.28, 7.26, 7.29, respectively; P < .01, Scheffé). Factors that significantly and independently predicted intubation among all neonates included exposure to general anesthesia (odds ratio [OR] 4.1; 95% confidence interval [CI] 1.9, 8.9) and lower infant weight (OR 10.1 per kg decrease; CI 5.1, 20). Factors predicting UA pH at most 7.15 included preeclampsia (OR 3.0; CI 1.5, 5.9) and older maternal age (OR 1.3 per 5 years; CI 1.02, 1.64); vertex delivery (OR 0.5; CI 0.2, 0.9) was protective. Factors predicting a 5-minute Apgar less than 7 were meconium (OR 1.5 per category going from none to terminal to light to heavy; CI 1.04, 2.3), general anesthesia (OR 6.9; CI 2.6, 18.2), lower infant weight (OR 16.5 per kg decrease; CI 7.8, 34.5), and vaginal breech delivery (OR 7.0; CI 1.8, 28.6); cesarean delivery (OR 0.2; CI 0.08, 0.66) was protective. Spontaneous vertex delivery raised the UA pH, and preeclampsia, amnioinfusion, breech delivery, and general anesthesia significantly and independently lowered the UA pH among all neonates. For infants delivered by cesarean, "fetal distress," preeclampsia, previous spontaneous abortion, failed forceps use, and nalbuphine significantly and independently predicted lower UA pH. CONCLUSION: Risk factors for poorer immediate neonatal outcomes among growth-restricted neonates include preeclampsia, fetal distress, breech delivery, forceps use, nalbuphine during labor, lower infant weight, and general anesthesia.

Analgesics, Opioid↗

PubMed1998

The effect of physician characteristics on compliance with adult preventive care guidelines.

BACKGROUND AND OBJECTIVES: This study identified physician characteristics and attitudes related to self-reported compliance with adult prevention guidelines. METHODS: A questionnaire was mailed to family practice and internal medicine residents and faculty at the University of Iowa (n = 209). The questionnaire's 78 items fell into seven categories, including physician demographics, history-taking practices, counseling practices, self-perceived effectiveness in changing patient behavior, beliefs about preventive care, knowledge about preventive care, and perceived barriers to the delivery of preventive care. RESULTS: Compliance with history-taking recommendations was independently associated with high knowledge scores, female physician gender, and high self-perceived effectiveness in changing patient behavior. The only factor that was independently associated with counseling efforts was self-perceived effectiveness in changing patient behavior. CONCLUSIONS: Factors that were independently associated with self-reported preventive care efforts include female physician gender, knowledge about preventive care guidelines, and perceived effectiveness in changing patient behavior. After controlling for these factors, other variables such as lack of time, lack of reminder systems, attitudes about preventive care, and amount of formal preventive care education were not related to self-reported compliance with counseling and history-taking recommendations.

Adult↗

PubMed1998

Sample size calculations based on slopes and other summary statistics.

Sample size calculations based on two-sample comparisons of slopes have been reported by many. This paper extends such discussions to include summary statistics other than slopes, such as post-baseline means, change scores, and final observations. Specifically, sample size formulas for analyses based on a broad class of summary statistics are presented, with modifications proposed to allow for missing data caused by staggered entry and random dropouts. The formulas developed are used to illustrate how required sample size is affected by summary statistic choice, variance parameters, the type of treatment difference of interest, and the manner in which incomplete observations are used in the analysis. An example based on longitudinal data from the Muscatine Study is presented.

Adolescent↗

PubMed1997

Anal incontinence after anal sphincter disruption: a 30-year retrospective cohort study.

OBJECTIVE: To compare the prevalence of anal incontinence remote from delivery (approximately 30 years postpartum) in 29 women whose index delivery was complicated by anal sphincter disruption versus a matched control group of 89 women who had an episiotomy without extension to the anal sphincter and versus a group of 33 women who delivered via cesarean. METHODS: In this retrospective cohort study, a structured questionnaire was sent to women in the above categories who delivered at a university hospital between 1961 and 1965 and for whom we could obtain current addresses. Outcome measures included frequent fecal and flatus incontinence and bothersome fecal and flatus incontinence. RESULTS: The three groups did not differ significantly in age, weight, age at delivery, parity, weight of largest baby, postmenopausal status, estrogen replacement usage, most medical conditions, or rectocoele, rectovaginal fistula, or incontinence surgeries. Frequent flatus incontinence was reported by nine (31.0%), 38 (42.7%), and 12 (36.4%) women in the anal sphincter disruption, episiotomy, and cesarean groups, respectively (not significant). The number of women with bothersome flatus incontinence was higher in the anal sphincter disruption group: 17 (58.6%) versus 27 (30.3%) in the episiotomy only group and versus five (15.2%) in the cesarean group (P = .001). Frequent fecal incontinence was reported by two (6.9%), 16 (18.0%), and 0 women (P = .008 between cesarean and episiotomy only groups), whereas bothersome fecal incontinence was reported by eight (27.6%), 23 (25.8%), and five (15.2%) women (not significant) in the anal sphincter disruption, episiotomy only, and cesarean groups, respectively. CONCLUSION: Regardless of the type of delivery, anal incontinence occurs in a surprisingly large number of middle-aged women.

Anal Canal↗

PubMed1997

Value of preoperative CA 125 level in the management of uterine cancer and prediction of clinical outcome.

OBJECTIVE: To enhance cost-effective management of uterine cancer by predicting the likelihood of extrauterine disease and survival on the basis of preoperative parameters. METHODS: A retrospective review of preoperative CA 125 levels from 210 women with endometrial carcinoma was performed. The relationship of preoperative CA 125 levels to various preoperative and postoperative histopathologic factors was investigated. RESULTS: Elevated CA 125 (greater than 35 U/mL) correlated (P < .05) with higher stage, higher grade, increased depth of myometrial invasion, positive cytology, pelvic or para-aortic lymph node metastases, and reduced actuarial survival (P < .001). Multivariate analysis of preoperative factors showed that an elevated CA 125 level was the most important predictor for poor survival (P < .001). Moreover, a preoperative CA 125 level greater than 65 U/mL was the most significant predictor of extrauterine disease and carried a 6.5-fold higher risk (95% confidence interval 2.5, 17.1). A logistic model to predict extrauterine disease was developed. The model has a sensitivity of 62%, specificity of 91%, positive predictive value of 69%, and negative predictive value of 88%. CONCLUSION: A CA 125 level should be included as part of the preoperative workup for all patients with uterine cancer. Patients with a preoperative CA 125 level less than or equal to 20 U/mL should be considered as candidates for vaginal hysterectomy unless unfavorable histology or a high-grade (grade II or III) tumor is present. In our series, this approach would have eliminated 24% of the abdominal staging procedures, with a risk of less than 3% for extrauterine disease, while lowering treatment-related morbidity and cutting costs in the treatment of this common female cancer.

Adult↗

PubMed1997

An introduction to time-trend analysis.

Healthcare professionals often are presented with data that appear to indicate an upward or downward trend over time. For example, admissions of acquired immunodeficiency syndrome (AIDS) patients appear to be increasing, cesarean section rates appear to be decreasing, or nosocomial pneumonia rates appear to be increasing. Critical decisions sometimes are based on such trends, which often are presented without a statistical analysis. Those responsible for decision making may be left wondering whether these apparent trends represent only chance variation. Graphs showing trends over time generally present one of three kinds of outcome data: counts (eg, three AIDS admissions), proportions (eg, 10 cesarean sections per 100 total deliveries), or person-time data (eg, 13 cases of nosocomial pneumonia per 10,000 patient days). Using familiar examples and a minimum of technical language, we illustrate the analysis of time trends.

Data Interpretation, Statistical↗

PubMed1997

Skills that Iowa family physicians desire in a new physician partner.

BACKGROUND AND OBJECTIVES: The importance of specific skills in primary care continues to be debated. As a result, there is not consensus on which skills need to be stressed during residency training. Our project asked community-based family physicians to rate the importance of specific skills in a new family physician partner. METHODS: Data were collected through a cross-sectional survey of all active members of the Iowa Academy of Family Physicians. Participants were surveyed by mail, using a list of 83 skills pertinent to primary care. Physicians were asked to rate the importance of a new member of their practice having the individual skills on this list. RESULTS: A total of 546 family physicians (67%) completed questionnaires. Fourteen skills (seven cognitive and seven psychomotor) were reported to be "essential" or "very important" by at least 80% of the physicians. A total of 43 skills were rated as "essential" or "very important" by at least 50% of responding family physicians. Many of the hospital-based procedural skills, particularly those used in an intensive care setting, were rated as less important. The importance ratings of many skills were associated with the physicians' ages, size of their primary hospitals, and availability of other medical specialties. CONCLUSIONS: Family physicians tended to rate office-based procedural skills, counseling skills, and management skills as "essential or very important" to their practices. These rating might be used to guide residency training in family practice.

Clinical Competence↗

PubMed1996

The effects of smoking on ovarian function and fertility during assisted reproduction cycles.

OBJECTIVE: To investigate the effects of cigarette smoking on ovarian function and fertility in women undergoing assisted reproduction cycles. METHODS: We assessed the effects of smoking on ovarian function and fertility in a cohort of 499 women. Questionnaires were designed to quantify past smoking exposure and to determine whether the woman was smoking during the treatment cycle. Ovarian function characteristics and pregnancy rates were compared among current smokers, past smokers, and nonsmokers. RESULTS: Compared with nonsmokers, both current and past smokers have reduced gonadotropin-stimulated ovarian function. A history of increasing tobacco exposure was associated with decreasing serum estradiol concentrations, numbers of retrieved oocytes, and numbers of embryos. On average, for every 10 pack-years of cigarette smoking, 2.5 fewer mature oocytes and 2.0 fewer embryos were obtained. Women who smoked during their treatment cycle had approximately a 50% reduction in implantation rate and ongoing pregnancy rate compared with women who had never smoked. Women who quit smoking before their treatment cycle had the same pregnancy rate as nonsmokers. CONCLUSION: Cigarette smoking is associated with a prolonged and dose-dependent adverse effect on ovarian function. Smoking appears to have a more transient toxic effect on fertility, because current smokers, but not past smokers, had a markedly reduced pregnancy rate after treatment cycles compared with nonsmokers. Women should quit smoking before assisted reproduction cycles.

Adult↗

PubMed1996

Vancomycin-resistant enterococcal bacteremia: natural history and attributable mortality.

Previous studies have shown that bacteremia due to vancomycin-resistant Enterococcus species (VRE) is associated with mortality of 17%-100%, but comorbid conditions may have confounded the estimates. We designed a historical cohort study to determine the mortality attributable to VRE bacteremia. Twenty-seven patients with VRE bacteremia were identified as cases. Within 7 days of the onset of bacteremia, severe sepsis developed in 12 patients (44%) and septic shock developed in 10 (37%). Case patients were closely matched to control patients without VRE bacteremia (1:1) by time of hospitalization, duration of exposure, underlying disease, age, gender, and surgical procedure. The mortality was 67% among cases and 30% among matched controls (P = 0.1). Thus, the mortality attributable to VRE bacteremia was 37% (95% confidence interval [CI], 10%-64%) and the risk ratio for death was 2.3 [CI, 1.2-4.1). We conclude that VRE bacteremia is associated with high rates of severe sepsis and septic shock. The attributable mortality approaches 40%, and patients who have VRE bacteremia are twice as likely to die than closely matched controls.

Adult↗

PubMed1996

Interinnominate motion and symmetry: comparison between gymnasts and nongymnasts.

Some clinical approaches to the treatment of low back pain evaluate and treat observed asymmetries of pelvic posture and motion. Scientific evidence suggests the motion available between the innominate bones is small and variable in nature. The purposes of this investigation were 1) to determine if interinnominate motion of subjects without low back pain was symmetrical in reciprocal test posture combinations, 2) to assess innominate bone symmetry in standing, and 3) to determine if a difference in the magnitude of interinnominate motion was present between a subject group which performs more frequent flexibility activities compared with a subject group representing the general population. Thirty-four subjects (eight male gymnasts, nine female gymnasts, eight male nongymnasts, and nine female nongymnasts) were evaluated in standing and three other reciprocal postures (modified standing, modified sitting, and half-kneeling). In each posture, the Metrecom Skeletal Analysis System was used to obtain coordinates for the anterior and posterior iliac spines. Projection angles were used to determine the relative positions of the right and left innominate bones. Results suggest that stand to right modified standing and stand to left modified standing oblique sagittal interinnominate composite motions were symmetrical, stand to right modified sitting and stand to left modified sitting oblique sagittal interinnominate composite motions were asymmetrical, and stand to right half-kneel and stand to left half-kneel oblique sagittal interinnominate composite motions' symmetrical properties were mixed depending on the group. Gymnasts as a group were found to have asymmetrically positioned innominate bones while nongymnasts as a group had symmetrically positioned innominate bones.

Adolescent↗

PubMed1996

Benign fever following vaginal delivery.

BACKGROUND: In patients with fever following vaginal delivery, physicians must differentiate benign self-resolving fevers from fevers with more serious causes, especially endometritis. To help differentiate these clinical entities, we explored the characteristics and risk factors for benign "single-day" postpartum fever. METHODS: We conducted a retrospective cohort study of 2137 vaginal deliveries. Patients were randomly selected from the 25,687 vaginal deliveries that took place between 1979 and 1992 at The University of Iowa Hospitals and Clinics. The data were analyzed using odds ratios and multiple logistic regression. RESULTS: Benign fevers occurred in 3.3% of patients, while endometritis was diagnosed in 1.6%. After controlling for confounding variables, two clinical factors were independently associated with single-day fever: primiparity (odds ratio [OR], 3.4; 95% confidence interval [CI], 2.0 to 5.7) and use of a uterine pressure catheter (OR, 2.4; 95% CI, 1.5 to 3.7). These factors were not associated with endometritis. The first postpartum temperature elevation ( > or = 38.0 degrees C) occurred earlier in patients with single-day fever than in patients with endometritis (4.0 +/- 4.6 hours postpartum vs 30.2 +/- 27.0 hours postpartum, P < .001). The maximum temperature elevation was lower, on average, in patients with single-day fever than in patients with endometritis (38.2 degrees +/- 0.2 degrees C vs 38.9 degrees +/- 0.6 degrees C, P < .001). CONCLUSIONS: Single-day fever was more likely to occur in primiparous women and in women who were monitored with a uterine pressure catheter. Most women with benign single-day fevers had early low-grade fevers, whereas women with endometritis had higher fevers that occurred later in the postpartum period.

Adult↗

PubMed1996

Understanding logistic regression analysis through example.

Logistic regression is a valuable statistical tool that is often used in primary care research. When researchers explore the association between a possible risk factor and a disease, they attempt to control the effects of extraneous factors (confounders) that can obscure the true association. Using logistic regression, researchers can simultaneously control for the effects of multiple confounders. When investigators use logistic regression, they make subjective decisions about which factors to include in the analysis and in the final predictive model. Critical readers must understand basic concepts of logistic regression and potential problems with its use before they can accurately interpret study results. This article uses a familiar example to explain the principles of logistic regression to make it understandable to nonstatisticians.

Coffee↗

PubMed1996

Practice patterns during the third stage of labor: the effect of physician age and specialty.

BACKGROUND: Elective manual removal of the placenta and routine uterine exploration following vaginal delivery are controversial procedures. Although advocated in the past, little is known about current attitudes and practices related to these procedures. METHODS: Using a mailed questionnaire, we surveyed all 178 Iowa obstetrician-gynecologists and a random sample of 163 Iowa family physicians to determine their practice patterns related to selected aspects of the third stage of labor. The data were analyzed using odds ratios and multiple logistic regression. RESULTS: The analysis was based on answers from 302 physicians. Physicians in the oldest age quartile were three times more likely than physicians in the youngest age quartile to routinely explore the uterus after a vaginal delivery (P < .01). After controlling for specialty, younger physicians were more likely to believe that manual removal of the placenta is a risk factor for endometritis (adjusted odds ratio [OR] 0.7 for each 10-year increase in age, 95% confidence interval [CI] 0.6 to 1.0). Controlling for age, family physicians were more likely than obstetrician-gynecologists to routinely order prophylactic antibiotics after manually removing the placenta (adjusted OR 2.0, 95% CI 1.1 to 3.7). CONCLUSIONS: Both physician age and specialty were associated with selected practice patterns involving the third stage of labor. Older physicians were less likely to believe that manually removing a placenta increases the risk of postpartum endometritis, and they were more likely to routinely explore the uterus after a vaginal delivery.

Adult↗

PubMed1995

The association between manual removal of the placenta and postpartum endometritis following vaginal delivery.

OBJECTIVE: To determine whether manual removal of the placenta after vaginal delivery is a risk factor for postpartum endometritis. METHODS: A retrospective cohort study of vaginal deliveries compared 1052 patients who had manual removal of the placenta with 1085 patients whose placentas delivered spontaneously. Subjects were selected randomly from the 25,687 vaginal deliveries at the University of Iowa Hospitals during 1979-1992. The presence of endometritis was determined using information in medical records. The data were analyzed using odds ratios (OR) and multiple logistic regression. RESULTS: After controlling for confounding variables, manual removal of the placenta was associated with postpartum endometritis (adjusted OR 2.9, 95% confidence interval [CI] 1.7-4.9). Other risk factors for endometritis included maternal age less than 17 years (OR 3.3, 95% CI 1.5-7.2), postpartum anemia (OR 2.9, 95% CI 1.9-4.5), and membranes ruptured longer than 24 hours (OR 2.5, 95% CI 1.4-4.3). CONCLUSION: Manual removal of the placenta is a risk factor for postpartum endometritis after vaginal delivery.

Adult↗

PubMed1994

Stratification of summary statistic tests according to missing data patterns.

Summary statistics, such as slope or area under the time-response curve, reduce the dimensionality of repeated measures data and can thereby simplify the comparison of groups in longitudinal studies. Since summary statistic distributions vary according to the amount, timing, and type of any missingness that occurs, one must choose between analysing the data unconditionally or conditionally on the missingness patterns. This paper uses simulations to compare such unstratified and stratified summary statistic analyses with respect to their size and power under models that allow for both non-informative and informative missingness mechanisms. Of particular interest is the robustness of these methods to violations of the assumptions that one must make if they are to have proper test size. It is found that stratification of the analysis tends to result in an increase of power, and improves the robustness to violations of missing data assumptions.

Computer Simulation↗

PubMed1993

Size and power of two-sample tests of repeated measures data.

One method of using repeated measures data to compare treatment groups in a clinical trial is to summarize each subject's outcomes with a single summary statistic, and then perform a distribution-free comparison based on the resulting statistics. We examine extensions of this approach and conditions under which they retain proper size in the presence of missing data. The asymptotic relative efficiencies of several summary statistic tests are calculated to show which perform best in a variety of situations. The techniques are illustrated using data from an AIDS clinical trial.

Analysis of Variance↗

PubMed1991

Analyzing laboratory marker changes in AIDS clinical trials.

Repeated measurements of laboratory markers of immunologic or disease status, such as CD4 lymphocyte counts and HIV p24 antigen levels, can be important end points in comparative clinical trials. In this report, we consider comparison of treatment groups with respect to such markers, focusing on a distribution-free approach in which each participant's data are characterized by a single summary statistic. The summary statistics examined are (a) the slope of the least-squares regression of the marker, (b) the average of the last r measurements, and (c) the difference between the averages of the last r and the first s measurements. Under various models of marker time trends, these methods are compared with regard to statistical power. It is found that the slope is usually more efficient than the other two types of summaries. Adaptations for missing data are discussed and illustrated in an analysis of CD4 counts from a recent AIDS clinical trial.

Acquired Immunodeficiency Syndrome↗

PubMed1990

Decontamination of instruments and control of cross infection in general practice.

OBJECTIVE: To assess the effectiveness of decontamination procedures in general practice. DESIGN: Anonymous postal questionnaire survey of 600 general practitioners randomly selected from the national register. SETTING: General practices throughout the United Kingdom. SUBJECTS: 382 General practitioners, a response rate of 65%. RESULTS: 186 General practitioners had autoclaves but 125 used hot water disinfectors or chemical disinfectants to reprocess instruments. 22% (474/2132) Of high risk instruments were inadequately decontaminated. Decontamination was performed by the practice nurse or receptionist in 306 practices. Knowledge of treatment of spillages of blood fluids was uncertain, and only 114 general practitioners used effective methods for dealing with spillages. CONCLUSIONS: A comprehensive central code of practice for control of infection is needed for primary health care staff.

Cross Infection↗