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J F Reed

Publications and source records attributed to J F Reed.

At least 55 records · Page 3Linked to original sources
PubMed1993

A Monte Carlo investigation of the robustness of the Wald, likelihood Ratio, and Median tests with specified symmetric and asymmetric marginal distributions.

The effect of nonnormality on the Type I (tau) error when comparing two independent binomial proportions (P) or the nonparametric alternatives, the Median (Me), Wald (W), and Likelihood Ratio (LR), has not been investigated. If these selected tests are overly conservative the implied loss of power would moderate their practical use. The purpose of the present study was to investigate the impact of nonnormality on small to moderate sample sizes on the estimated tau for alpha = 0.10, 0.05, and 0.01 for the P, Me, W, and LR tests. Samples were generated from nine long-tailed symmetric and asymmetric distributions using a multiplicative congruential generator. For each marginal distribution and for a variety of sample sizes, the proportion of samples for which the test statistic exceeded the 10, 5, and 1 percentage points was tabulated. For data that mimic a symmetric distribution, the median test uniformly yields an empirical alpha considerably less than tau, while the likelihood ratio test consistently overestimates tau for small samples (n < or = 15) over all symmetric distributions and empirical alpha levels. For asymmetric distributions, the median test again yields an empirical alpha significantly less than tau. Similar underestimates of tau were found for the chi-square (2 df), chi-square (4 df) log normal, and gamma (2, 1) distributions. The likelihood ratio test consistently overestimates tau for small samples (n < or = 15) over all asymmetric distributions and empirical alpha levels. The independent proportions test produces an empirical alpha closest to tau for n = 10 for all asymmetric distributions.(ABSTRACT TRUNCATED AT 250 WORDS)

Data Interpretation, Statistical↗
PubMed1993

Rapid assessment of human immunodeficiency virus seroprevalence in a community-based hospital.

BACKGROUND: To aid in development of patient testing policy, in-service education, and resource planning, it is necessary to have a useful and meaningful tool for determining the population-specific HIV seroprevalence rate for our hospital patients. We were offered by the Centers for Disease Control a newly developed survey tool: "Rapid Assessment of HIV Seroprevalence in Hospital Patients." We subsequently served as one pilot site for this tool. METHODS: A population-based sample of 1000 patients (500 inpatients, 500 outpatients) was stratified into age and sex groups on the basis of admission statistics from the previous year in a general community hospital system in southeastern Pennsylvania that consists of two clinical campuses: an urban site with 343 beds and a suburban site with 506 beds. The study was conducted as an anonymous, unlinked screening for HIV antibody in 1000 serum samples. RESULTS: We found our overall seroprevalence rate to be 2.60% (Poisson 95% confidence interval, 1.77% to 3.81%), or 1 in 38 patient specimens. The highest rates for both sexes were found in the age range 25 to 44 years. CONCLUSIONS: This protocol is a useful survey tool for community hospitals to determine the HIV seroprevalence rate in patient populations, a practical necessity for planning and education. Survey results would aid in implementation of current Centers for Disease Control guidelines for HIV testing of inpatients and outpatients in the acute care hospital setting.

Acquired Immunodeficiency Syndrome↗
PubMed1993

The relationship between the arteriovenous carbon dioxide gradient and cardiac index.

It has been reported that under normal conditions, mixed venous blood gases have approximated arterial samples; however, during cardiac arrest or severe cardiogenic shock, marked differences between arterial and venous blood gases have been noted. To further assess the relationships between arterial and mixed venous blood gases and cardiac index, a study population was chosen consisting of patients with less severe states of cardiac impairment. The differences between arterial and mixed venous PCO2s and pHs were compared with cardiac indexes (CI) of 44 patients in an intensive care unit with arterial lines and Swan-Ganz catheters in place. Twenty-six patients with normal CIs (2.6 to 4.1 L/min/m2) had a mean difference in mixed venous-arterial PCO2 (delta PCO2) of 4.88 +/- 0.40 mm Hg. In patients with low CIs (< 2.6), the delta PCO2 was 7.44 +/- 0.63 mm Hg (P = .001). The difference of mixed venous and arterial pH (delta pH) was 0.027 +/- 0.004 pH units for patients with normal CIs and 0.04 +/- 0.003 pH units for those with low CIs (P < .002). When the CIs of all patients were plotted against the delta PCO2s, there was an inverse linear relationship wherein delta PCO2 increased as CI decreased (r = -.47, P = .0011). There is an inverse relationship between delta PCO2 and CI that has not been previously described. An elevated delta PCO2 may be a marker of a low cardiac index.

Aged↗
PubMed1993

Biomechanics of ocular pneumoplethysmography.

A mathematical analysis of ocular pneumoplethysmography is presented, based on the physiological, anatomical, and biomechanical properties of the eye. Ocular pneumoplethysmography is a clinical procedure involving elevation of intraocular pressure, by application of a suction cup to the sclera, to a level that exceeds ophthalmic artery systolic pressure. As decay in intraocular pressure is allowed, return of retinal artery pulsations indicates ophthalmic artery systolic pressure. We obtain a quantitative relationship between increase in intraocular pressure and applied vacuum, and compare the theoretical predictions with experiments on rabbits in which a variable descending vacuum was applied to bilateral scleral eyecups. The bilateral intraocular pressures were simultaneously recorded from cannulae in the respective vitreous bodies, and the pressures at which return of ocular pulsations were observed were correlated with the scleral vacuums. Regression lines were calculated for three serial determinations in each animal, with two groups of animals distinguished by the inner diameter of the eyecups used. The theoretical results indicate that the relationship between intraocular pressure increase and applied vacuum is independent of Young's modulus, and depends primarily on the ratio of the diameter of the vacuum cup to the diameter of the eye.

Animals↗
PubMed1993

The impact of cardiac index on cerebral hemodynamics.

BACKGROUND AND PURPOSE: Current noninvasive testing allows accurate assessment of cerebrovascular hemodynamics. The cardiovascular influence on the noninvasive assessment of cerebrovascular studies has not been defined. This study was designed to determine the effect of cardiac index (CI) on cerebral blood flow velocities, ocular pulse amplitude, ophthalmic systolic pressure, and ocular blood flow (OBF) as currently estimated by noninvasive laboratories. METHODS: Based on a retrospective study of 181 patients, we prospectively evaluated 45 patients undergoing right heart catheterization for hemodynamic monitoring to correlate the relation between CI, transcranial Doppler sonography, and ocular pneumoplethysmography. Patients with hemodynamic instability, severe carotid stenoses, massive cerebral infarct, or sepsis were ineligible for the study. Simultaneous recordings of systemic blood pressure, ophthalmic systolic pressure, heart rate, ocular pulse amplitude, middle cerebral artery blood flow velocities, and cardiac output were obtained on all patients. OBF was calculated from the heart rate and ocular pulse amplitude. RESULTS: The relation between OBF and CI is expressed by the equation CI = 2.36 + 0.61 x OBF (r = .47, P = .0010). The middle cerebral artery peak systolic velocities and CI had a correlation of .36 (P = .0181). The equation, derived from the linear relation between OBF and CI, was then validated on a sample of 15 patients. With the apparent linear relation between OBF and CI, we used the derived equation to predict CI from OBF. The OBF determination predicted CI within 30% in all patients and within 20% in 53.3% of the patients. CONCLUSIONS: We demonstrated that OBF and middle cerebral artery systolic velocity decrease with diminishing CI. Our findings suggest that CI may be potentially estimated in selected patients by noninvasive assessment of OBF using ocular pneumoplethysmography.

Blood Pressure↗
PubMed1993

The cerebral hyperperfusion syndrome: diagnostic value of ocular pneumoplethysmography.

PURPOSE: There were two purposes to our study. The first was to characterize the ocular hyperperfusion associated with carotid endarterectomy. The second was to relate ocular hyperperfusion to the clinical presentation of cerebral hyperperfusion syndrome. METHODS: This was a retrospective chart review of 2331 patients who underwent carotid endarterectomy at our institution between June 1978 and May 1991. RESULTS: Twelve of these carotid endarterectomies were associated with ocular hyperperfusion on the side of operation. Clinical evidence of cerebral hyperperfusion syndrome was observed in five of these 12 procedures. In these five patients there were two associated fatal intracerebral hemorrhages and one permanent coma. In the latter three patients the contralateral internal carotid arteries were totally occluded. CONCLUSION: Ocular hyperperfusion, as documented with ocular pneumoplethysmography, is useful in alerting the physician to the potential for development of the cerebral hyperperfusion syndrome.

Air↗
PubMed1992

Data management of an inflammatory bowel disease registry.

The history and etiology of inflammatory bowel disease which is characterized by two major disease processes: ulcerative colitis and Crohn's disease, remain unknown. Research is focussing on seven major areas of genetic, environmental and physiologic factors that apparently relate to this disease. Based on this background, a population based Inflammatory Bowel Disease Registry was established in 1987 in the Lehigh Valley area of southeastern Pennsylvania. Consent forms, patient data forms and protocols for operation and implementation were developed, and databases were designed to accommodate demographic, basic history, follow-up and relative history data. The databases were correlated with an IBD registry ID number which both enabled relational analyses and ensured confidentiality of data information. The registry continues to grow, providing feedback for both continued medical research and supportive information for IBD patients and their physicians.

Database Management Systems↗
PubMed1992

Concordance of familial characteristics in Crohn's disease and ulcerative colitis.

The diagnosis of inflammatory bowel disease (IBD) in a proband increases the probability of a parallel IBD diagnosis in a family member. In this study, we were able to confirm the IBD diagnosis in 35 (9.9 percent) of the relatives of 352 registry probands. To confirm a proband's report of a positive family history of IBD, efforts were made to directly contact all first-degree relatives regardless of their IBD status (parents, siblings, and children). Consent to contact family members was obtained from the proband, who furnished the registry personnel with names, addresses, and phone numbers. We then attempted to contact each identified relative by phone. After verbal consent was obtained, family members were asked if they had been diagnosed with IBD. This diagnosis was confirmed by contacting the relative's physician. A McNemar (chi 2 Mc) matched-pair analysis was used to analyze concordance between the proband and the affected family member. Within the CD/CD (Crohn's disease) concordant pairs, sex was a significant risk factor. Sex was not a significant risk factor within the UC/UC (ulcerative colitis) concordant pairs. In the concordant surgery pairs, no surgical procedure was a significant risk factor for the prediction of a similar surgical procedure for the affected relative. In concordant extraintestinal complications, only the appearance of a skin rash was significantly related to the appearance of a skin rash in the affected relative.

Colitis, Ulcerative↗
PubMed1992

Cohen's weighted kappa with Turbo Pascal (FORTRAN).

A microcomputer based Turbo Pascal and FORTRAN program for Cohen's weighted kappa (kappa w) is given. Three clinical applications for kappa w are also presented. A typical data file, the Pascal and FORTRAN program listing and corresponding output are given.

Carotid Stenosis↗
PubMed1992

Risk factors for stroke after coronary artery bypass.

To determine the prevalence of stroke after coronary artery bypass grafting and to evaluate risk factors, we reviewed the records of 1000 patients undergoing coronary bypass within a 1-year time period. Demographic and perioperative data were evaluated by chi 2 analysis. A history of diabetes, evidence of mural thrombus, positive oculopneumoplethysmography findings, increased age, aortic calcification, and postoperative arrhythmias all correlated with increased risk of permanent neurologic deficit for the patient undergoing coronary bypass. Risk factors were analyzed with stepwise logistic regression. A history of diabetes, presence of mural thrombi, and aortic calcification carried a higher probability that the patient would have a permanent neurologic deficit.

Aged↗
PubMed1992

Impact of human immunodeficiency virus on medical and surgical residents.

BACKGROUND--Previous surveys of resident physicians on human immunodeficiency virus (HIV) matters have tended to focus on urban programs serving a patient population with an expected high prevalence of HIV infection. The objective of this study was to survey a community hospital residency program in a nonurban area with a perceived low HIV patient seroprevalence. METHODS--A 32-question survey was completed on an anonymous basis by the entire 74 member multidisciplinary resident physician group at a two-campus university-affiliated hospital program in southeastern Pennsylvania in May 1991. RESULTS--Residents perceived their patient population's HIV seroprevalence rate to be low although they believed their personal risk of occupational exposure to blood-borne infection was moderate to high. House staff most often complied with universal precautions for fear of acquiring a blood-borne illness and most often did not comply because of time constraints. Not perceiving the exposure as a health risk was the primary reason for nonreporting of exposures. Occupational exposure rates were alarmingly high, with suturing using a curved needle being the most common exposure method. Most residents were unfamiliar with HIV legislation. A majority of the house staff wanted improved HIV patient management training and life and disability insurance against occupationally acquired HIV. Many other important issues were addressed in this survey. CONCLUSION--Residents even in low seroprevalence environments do fear occupationally acquired HIV. A great need exists for improved training in universal precautions, acquired immunodeficiency syndrome legislation, and HIV patient management as well as for insurance against occupationally acquired HIV.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Utility of combining two diagnostic tests.

Methods for evaluating a single diagnostic test with reference to the disease prevalence in a given population include sensitivity, specificity, positive predictive value, negative predictive value, and accuracy. Patient disease status and, ultimately, the treatment course is determined by the outcome of these diagnostics. The advantage of ordering a single diagnostic test, or series of diagnostic tests is a concern of physicians. How much information is gained from using the results of two diagnostic tests, each designed to detect the same disease? Combining tests may be the optimal methodology for determining the disease status of the patient. We propose a systematic strategy for optimizing (minimizing alpha and/or beta errors) the combination of two diagnostic tests. This strategy is then illustrated by the use of data from Doppler ultrasound and ocular pneumoplethysmography in detecting carotid artery disease.

Carotid Artery Diseases↗
PubMed1991

Assessment of disease activity in a registry of Crohn's disease patients in eastern Pennsylvania.

The objectives of this report are to: 1) compare the Crohn's disease (CD) patient's assessment of their well-being to the physician's assessment of the patient's well-being, 2) use the existing Crohn's disease indices (CDI) in comparing the severity of CD with the patient's self assessment, and 3) compare the CDI with the physician's assessment of patient well-being. The CDI included in this study were the National Cooperative Crohn's Disease Study Index (CDAI), Harvey & Bradshaw Index (HBI), Oxford Index (OXI), Modified-Organisation Mondiale de Gastroenterologie (OMGE), Cape Town Index (CTI), Bristol Index (BRI), St. Marks Index (SMI) and the Van Hees index (VHI). The patient and physician correlation of well-being was poor but statistically significant. The patient assessment of well-being was best measured by the CTI (r = 0.635, p less than or equal to 0.001), followed closely by the OMGE and CDAI (r = 0.615, p less than or equal to 0.001 and r = 0.582, p less than or equal to 0.001 respectively). The physician assessment of well-being was best measured by the VHI (r = 0.527, p less than or equal to 0.001).

Cohort Studies↗
PubMed1990

Significance of lumbosacral list and low-back pain. A controlled radiographic study.

A prospective study of 43 patients with low-back pain was performed to determine if there exists 1) a significant correlation between lumbosacral list and low-back pain, 2) a significant difference between measured list in patients pretreatment and posttreatment, and/or 3) a significant difference in results obtained using two different measuring techniques. All patients had standing antero-posterior radiographs. The radiographs were analyzed for lumbosacral list using two measurement methods. The results indicated that there was no significant correlation between lumbosacral list and low-back pain and no significant change in measured list in individuals pretreatment and posttreatment. There was a significant difference between the two methods described above. The intercristal line (ICL) method proved most precise.

Adult↗
PubMed1989

Duplex ultrasound and ocular pneumoplethysmography concordance in detecting severe carotid stenosis.

Concordance between two independent tests should serve to increase the accuracy of diagnosis. A combination of ocular pneumoplethysmography and duplex ultrasound, which uses high-resolution B-mode imaging plus spectral analysis, was used to evaluate 289 consecutive patients prior to biplane carotid angiography. Where there was concordance, the noninvasive tests predicted the presence or absence of hemodynamically severe carotid stenosis (75% or greater cross-sectional area reduction) with a sensitivity of 96.8%, a specificity of 95.9%, an accuracy of 96.2%, and positive and negative predictive values of 91.0% and 98.6%, respectively. Of the 538 study arteries, only four (0.74%) angiographically severe lesions escaped detection by both noninvasive tests. Sources of diagnostic error for both tests were defined. We believe that the combination of duplex ultrasound and ocular pneumoplethysmography significantly improves the overall assessment of carotid atherosclerosis.

Carotid Artery Diseases↗