Search PubMed⌕ Search

Biomedical subjects

M J Podgor

Publications and source records attributed to M J Podgor.

48 records · Page 3Linked to original sources
PubMed1985

Conjunctival sign in sickle cell anaemia: an in-vivo correlate of the extent of red cell heterogeneity.

A consecutive series of 22 stable adult inpatients with sickle cell anaemia were examined for the presence and severity of spontaneous 'comma' signs of the conjunctiva. Fifteen patients had severe conjunctival signs (more than 10 commas in the worse eye). The presence of severe conjunctival signs was associated with a broader distribution of intraerythrocytic haemoglobin concentrations (p = 0.0005). The patient group with severe conjunctival signs was not found to be significantly different from the group without such signs for age, sex, haemoglobin value, reticulocyte count, alpha-globin gene number, percentage fetal haemoglobin, or the proportion of very dense cells (CHC greater than 37 g/dl). Thus the singular heterogeneity of the erythrocytes in sickle cell disease may be indicative of the factor(s) responsible for the diagnostic comma sign.

Adult↗
PubMed1985

Correlation of ocular rigidity and blue sclerae in osteogenesis imperfecta.

A previous study of 16 patients and 16 controls had indicated that the mean ocular rigidity value was significantly lower in Osteogenesis Imperfecta (OI) patients than in normal controls (p = 0.001). These preliminary results have been confirmed in the present study of 46 patients and 53 controls where the difference in mean ocular rigidity between the patient and control group was statistically significant at the p less than 0.0001 level. Of particular interest was the inverse correlation between blueness of sclera and ocular rigidity in patients with OI. The establishment of such a relationship depended upon the availability of a larger sample size than had previously been examined.

Adolescent↗
PubMed1984

Assessing possible late treatment effects in stopping a clinical trial early: a case study. Diabetic Retinopathy Study report No. 9.

Suppose a fixed-sample trial in a disease with a long response time shows a statistically significant benefit of the experimental treatment before patients have completed the planned follow-up period. The question may then arise--and did arise in the Diabetic Retinopathy Study (DRS)--whether the observed early benefit of treatment may be offset at some time in the future by the subsequent development of harmful treatment effects. If this question raises serious concerns, then the investigators are faced with a dilemma. If the trial is stopped because of the observed early treatment benefit and the treatment is administered to the untreated control group as well as to patients outside the study, and if the treatment is later found to have deleterious effects, then it may ultimately do more harm than good to patients. Moreover, the fact that the treatment is harmful may never become known. If, on the other hand, the trial is not stopped and the treatment proves to have no deleterious effects, then the control group and patients outside the study would be harmed because the treatment was withheld. We show how, in the DRS, this very problem was formulated and resolved. First a severe, delayed harmful treatment effect was postulated. Projections based on this postulation showed that the early gains were so great that they were unlikely to be offset--ever. Based in part on these projections, the following decisions were made: (a) the study protocol would be changed so as to allow treatment of the untreated control group, and (b) patients would continue to be followed in order to make possible the detection of late, harmful treatment effects, should they develop.

Clinical Trials as Topic↗
PubMed1983

Incidence estimates for lens changes, macular changes, open-angle glaucoma and diabetic retinopathy.

Incidence data are lacking for common eye conditions. The authors previously developed a method for estimating incidence from age-specific prevalences for diseases that are irreversible and not associated with differential mortality (Am J Epidemiol 1981;113:606-13). This method is now used to estimate age-specific incidences for senile lens changes, senile cataracts, macular changes, senile macular degeneration, open-angle glaucoma, and diabetic retinopathy. Using age-specific prevalence data from the Framingham Eye Study, five-year incidence rates were estimated for ages 55, 60, 65, 70, and 75. For each condition, estimated incidence increased with age: incidence estimates ranged from 10% to 37% for senile lens changes, from 1% to 15% for senile cataracts, from 3% to 6% for macular changes, from 0.5% to 7% for senile macular degeneration, from 0.2% to 1% for open-angle glaucoma, and, among diabetics, from 3% to 5% for diabetic retinopathy. Standard errors were small for senile lens changes and senile cataracts, but large (of about the same magnitude as the incidence estimates) for macular changes, senile macular degeneration, open-angle glaucoma, and diabetic retinopathy. These estimates may be useful as approximations of the true incidence rates in planning epidemiologic research.

Aged↗
PubMed1983

Intraocular pressure, cardiovascular risk variables, and visual field defects.

This study evaluates the associations of intraocular pressure with cardiovascular risk factors among 2433 participants in the Framingham Eye Study and the Framingham Heart Study. Persons with intraocular pressure greater than 21 mmHg in at least one eye had an increased prevalence of hypertension and diabetes; no association was found with cardiovascular disease. In multiple regression analysis, systolic blood pressure was the variable most related to intraocular pressure; vertical cup/disc ratio, diabetes, and ventricular rate were also independently related to intraocular pressure. About 6% of the variation in intraocular pressure was explained by these variables. Although blood pressure was associated with intraocular pressure in eyes without visual field defects, this association could not be detected in eyes with field defects; interaction tests found significant differences in the blood pressure-intraocular pressure relationships between visual field groups. Ratios of blood pressure to intraocular pressure were lower in eyes with visual field defects than in eyes without field defects.

Blood Pressure↗
PubMed1982

Retinopathy in juvenile-onset type I diabetes of short duration.

We evaluated the prevalence and severity of diabetic retinopathy in 173 juvenile-onset, type I diabetic subjects and 78 nondiabetic controls of similar age, race, and sex distribution by stereoscopic fundus photography and fluorescein angiography, performed by a standardized protocol and evaluated by five expert, masked observers. The overall prevalence of retinopathy was 18% in the diabetic group and 0% in the controls. Retinopathy prevalence increased with duration of diabetes in the diabetic group, with a prevalence of 1% from 0--4 yr after diagnosis, 25% after 5--9 yr, and 67% 10--16 yr after onset of the systemic disease. There was an independent association with age, with little retinopathy before age 15 and a 48% prevalence in older persons. Retinopathy was also found to be independently associated with the following: diabetic "control," evaluated semiquantitatively but on a masked basis; lens opacities; and frequency of daily insulin injections. Among the 166 diabetic subjects who had both angiography and photography, a retinopathy prevalence of 17% was detected by angiography and 11% by photography. This difference was statistically significant (P = 0.01). This study provides baseline data for use in estimating sample size in controlled trials of therapeutic measures to prevent retinopathy in juvenile diabetic populations. The study also supports the hypothesis that long-term hyperglycemia as well as changes (possibly hormonal in nature) associated with puberty are causally related to diabetic retinopathy.

Adolescent↗
PubMed1981

Low ocular rigidity in patients with osteogenesis imperfecta.

Sixteen patients with osteogenesis imperfecta (OI) have undergone a thorough eye examination. These patients had statistically significantly lower ocular rigidity measurements than a group of normal volunteers matched on age, sex, and refractive error. In addition, the corneal diameter and length of the eyeball was smaller in OI patients than that in controls. Possible correlations of low ocular rigidity with biochemical changes in scleral collagen await further investigation.

Adolescent↗
PubMed1980

Retinopathy in juvenile-onset diabetes of short duration.

To study objectively the epidemiology of retinopathy in juvenile-onset diabetes, we performed fundus photography and fluorescein angiography, using the Diabetic Retinopathy Study protocol, on 122 juvenile diabetics and 65 demographically similar non-diabetic subjects as the control group. Photographs and angiograms were masked as to subjects' identities and evaluated independently by five retinal subspecialists. There was no retinopathy in control subjects. In diabetics, prevalence of retinopathy increased with the duration of disease, being 0% after zero to four years, 27% for five to nine years, and 71% for more than ten years. Retinopathy also increased in prevalence with age with a sharp rise after age 15. There is indication that age and duration act independently. Details of our method for establishing the diagnosis of diabetic retinopathy are presented, together with the degree of observer variability in identifying early lesions.

Adolescent↗
PubMed1979

Prognosis for life in patients with diabetes: relation to severity of retinopathy.

In a group of 709 individuals with diabetes diagnosed prior to age 50 and followed for five to thirteen years a strong inverse relationship was demonstrated between the severity of the retinopathy at the initial visit and survival. Survival in patients with no retinopathy or with microaneurysms only was little different from that of the general population (five-year rate .99, SE .01). The five-year survival rate for patients with more severe nonproliferative retinopathy, characterized by the presence of hemorrhages and/or exudates, but without new vessels or vitreous hemorrhage (B2), was .81 (SE .04), and that for patients with proliferative retinopathy (PDR) was .56 (SE .03). After adjustment for age at diagnosis of diabetes, duration of diabetes and sex, the differences in survival between these three groups were highly statistically significant. Impairment of visual acuity was also shown to be inversely related to survival. The five-year survival rate for patients with visual acuity of 20/200 or worse in each eye was .42 (SE .05). In patients with B2 retinopathy there was a weak but statistically significant trend towards decreasing survival with increasing duration of diabetes. In patients with PDR survival decreased with increasing duration up to 20 years, but then improved for patients with 20 years or more of diabetes.

Adolescent↗
PubMedDate not supplied

Estimating incidence from age-specific prevalence for irreversible diseases with differential mortality.

We present a method for estimating incidence from age-specific prevalence data for an irreversible disease where the mortality risks may differ for persons with and without the disease. This method is an extension of previously presented methodology for estimating incidence from prevalence for a disease that does not entail differential mortality. An application to senile cataract illustrates the method.

Age Factors↗
PubMedDate not supplied

On non-parametric and generalized tests for the two-sample problem with location and scale change alternatives.

Various tests have been proposed for the two-sample problem when the alternative is more general than a simple shift in location: non-parametric tests; O'Brien's generalized t and rank sum tests; and other tests related to the t. We show that the generalized tests are directly related to non-parametric tests proposed by Lepage. As a result, we obtain a wider, more flexible class of O'Brien-type procedures which inherit the level robustness property of non-parametric tests. We have also computed the tests' empirical sizes and powers under several models. The non-parametric procedures and the related O'Brien-type tests are valid and yield good power in the settings investigated. They are preferable to the t-test and related procedures whose type I errors differ noticeably from nominal size for skewed and long-tailed distributions.

Clinical Trials as Topic↗