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Biomedical subjects

M L Van Natta

Publications and source records attributed to M L Van Natta.

13 recordsLinked to original sources
PubMed2001

Photographic measures of cytomegalovirus retinitis as surrogates for visual outcomes in treated patients.

OBJECTIVE: To evaluate photographic measures of cytomegalovirus (CMV) retinitis as surrogate outcomes for changes in vision in patients with CMV retinitis related to the acquired immunodeficiency syndrome. METHODS: Data from 3 clinical trials of CMV retinitis treatments were analyzed. Two photographic assessments of retinitis in eyes involved at baseline were evaluated: progression (lesion border movement > or = 750 microm or occurrence of a new lesion) and change in area of retina involved with retinitis. Vision measures were decline in best-corrected visual acuity and change in visual field. Photographic measures were evaluated as surrogate outcomes based on 4 criteria: (1) association with vision measure; (2) ability to account for treatment-related differences in vision measure; (3) data completeness; and (4) sample size requirements. RESULTS: Data from 1001 involved eyes (666 patients) were analyzed. Progression and change in area involved were predictive of declines in vision measures, accounted for 50% and 66% of the treatment effect on visual field, and were available from 93% and 64% of involved eyes, respectively. Sample size estimates for a clinical trial were smallest with progression as the design outcome. CONCLUSION: Progression and change in area involved met the first and second criteria for surrogate outcomes for visual field loss; a complete evaluation for visual acuity decline was not possible because treatment-related differences were not observed. Progression met the logistical and sample size criteria better than change in area of retina involved with retinitis.

AIDS-Related Opportunistic Infections↗
PubMed2001

House dust mite and cockroach exposure are strong risk factors for positive allergy skin test responses in the Childhood Asthma Management Program.

BACKGROUND: Children with asthma have a high prevalence of environmental allergies, especially to indoor allergens. The relationships of exposure to indoor allergens (dust mites, cat, dog, cockroach, and molds) and other host factors to allergy sensitization have not been evaluated simultaneously in a large cohort. OBJECTIVES: We studied 1041 children aged 5 to 12 years with mild-to-moderate asthma to determine risk factors associated with having positive allergy skin test responses to indoor allergens. Also, we described, compared, and contrasted 6 allergens in the home environments of these children from 8 North American cities. METHODS: Data were used from baseline visits of the Childhood Asthma Management Program. Patients' sensitivities to house dust mites (Dermatophagoides farinae and Dermatophagoides pteronyssinus), cats, dogs, cockroaches, and molds were examined for relationships to demographic variables, home dust allergen exposures, number of other positive allergy skin test responses, total serum IgE levels, and smoking in the home. RESULTS: San Diego (78.5%) and Toronto (59.3%) had the topmost percentages of homes with moderate-to-high house dust mite levels. Boston (21.5%), St Louis (16.3%), and Baltimore (13.4%) had the highest percentages of homes with detectable levels of cockroach allergen. For house dust mites, the higher the level of allergen exposure, the more likely patients were to have positive allergy skin test responses, with relative odds of 9.0 (95% confidence interval, 5.4-15.1) for those exposed to high mite levels (>10.0 microg/g dust) relative to those unexposed. Even exposure to low levels of mite allergen (0.020-2.0 microg/g) was found to be a significant risk factor for sensitization. For cockroach allergen, those with detectable home exposure were more likely to have positive skin test responses (relative odds, 2.2; 95% confidence interval, 1.3-3.8) than those with undetectable exposure. In contrast, levels of exposure to cat, dog, and mold allergens were not related to sensitization rates. For cat allergen, this may reflect lower rates of cat ownership among highly sensitized subjects. Furthermore, the number of allergy skin test responses that were positive, excluding the test for the outcome of interest for each model, and total serum IgE levels were strong independent predictors of sensitization. CONCLUSIONS: Levels of exposure determined by house dust analysis are important determinants of sensitization for dust mite and cockroach allergen. This relationship was not demonstrable for cat, dog, or mold allergens, possibly because of confounding factors. For all allergens studied, the degree of atopy, determined by the total number of positive skin test responses or by total serum IgE levels, is an important contributing risk factor for sensitization.

Air Pollution, Indoor↗
PubMed2000

Relationship between increased airway responsiveness and asthma severity in the childhood asthma management program.

The relationship between increased airway responsiveness and asthma severity in children is unclear. The Childhood Asthma Management Program (CAMP) with 1,041 children with mild to moderate asthma offers an opportunity to relate the concentration of methacholine that causes a 20% fall in FEV(1) (PC(20)) to level of lung function, occurrence of respiratory symptoms, duration of disease, and assessment of severity by clinical staff. Decreasing PC(20) was found to be associated with lower levels of lung function (prebronchodilator percent predicted FEV(1): r = 0.29, beta = 3.5, p < 0.001), the occurrence of chronic asthma symptoms, persistent wheezing (odds ratio [OR] = 1.66, p < 0.001), subjective clinical staff assessment of asthma severity (p < 0.001), and longer duration of asthma (r = -0.11, beta = -0.20, p < 0.002). These data provide evidence that the degree of airway responsiveness is linked to disease severity in children with mild to moderate asthma.

Adolescent↗
PubMed1998

A placebo-controlled trial of a HEPA air cleaner in the treatment of cat allergy.

To evaluate the effect of a room high-efficiency particulate air (HEPA) cleaner on cat-induced asthma and rhinitis, 35 cat-allergic subjects who were living with one or more cats were studied in a double-blind, placebo controlled trial. After a 1 mo baseline period, subjects' bedrooms were equipped with an active or placebo air cleaner for the following 3 mo. Evaluations included monthly measurement of cat-allergen levels, daily morning, afternoon, and nighttime nasal- and chest-symptom scores, twice-daily measurement of peak-flow rates, daily medication scores, monthly spirometry, and methacholine (MCh) challenge testing before and after the study. Airborne allergen levels were reduced in the active-filter group as compared with the placebo group (p = 0.045). However, no differences were detected in settled-dust allergen levels (p = 0.485), morning, afternoon, or nighttime nasal-symptom scores (p = 0.769, 0.534, and 0.138), chest-symptom scores (p = 0.388, 0.179, and 0.215), sleep disturbance (p = 0.101), morning or afternoon peak-flow rates (p = 0. 424 and 0.679), or rescue medication use (nasal, p = 0.164, chest, p = 0.650), respectively. Although the combination of a HEPA room air cleaner, mattress and pillow covers, and cat exclusion from the bedroom did reduce airborne cat-allergen levels, no effect on disease activity was detected for any parameter studied.

Adult↗
PubMed1991

Hip fractures among the elderly: factors associated with in-hospital mortality.

Factors associated with mortality were examined for 27,370 hip fracture patients aged 65 years or older in Maryland hospitals, using discharge data for 1979-1988. Variables of interest included sociodemography, principal medical and injury diagnoses, E-code, year, disposition, and hospital. For both white males and white females, the hip fracture rate doubled with each 5-year increment in age. The overall proportion who died during hospitalization was 4.9% (n = 1,339). After multivariate adjustment, there remained a substantially increased risk of death for males. The relative odds (RO) of dying for males versus females were 1.6. Other factors associated with high relative odds of dying during hospitalization included the diagnosis of septicemia (RO = 12.3), pneumonia/influenza (RO = 4.9), and digestive system disorder (RO = 3.6). The RO of dying doubled in the presence of cardiac, neoplastic, or cerebrovascular disease. Patients with diagnoses of nervous system or mental disorder, hypertension, anemia, musculoskeletal system disease, or urinary tract infection were at decreased risk of dying. Results of the study suggest that the prevention or early diagnosis and treatment of serious infections in the elderly patient with a hip fracture remain an important challenge to clinicians.

Black or African American↗
PubMed1991

Risk factors associated with falls and injuries among elderly institutionalized persons.

A case-control study among 184 matched pairs of patients 65 years of age and older was undertaken to identify risk factors associated with falls and injuries in a long-term care facility in Baltimore, Maryland, in 1984-1985. Patients were matched on length of stay. Variables of interest included sociodemography, functional status, medications, and diagnoses. For all levels of care combined, the following factors were associated (p less than or equal to 0.01) with increased falls: being able to walk (relative odds (RO) = 4.0), age 90 years and older (RO = 3.8), a history of falling (RO = 5.0), and taking a vasodilator (RO = 3.0). Among the 184 fallers, the diagnosis of dementia (RO = 7.5) or taking a diuretic (RO = 7.2) was positively associated with injury (p less than or equal to 0.01). In each of the analyses, medications were associated with falls or injuries, suggesting a feasible intervention. The combination of a history of falling, being able to walk, and being 90 years of age or older increased the relative odds to 51.9 and could alert clinicians to identify and monitor high-risk elderly persons in need of preventive measures.

Accidental Falls↗
PubMed1989

A case-control study of aplastic anemia.

A case-control interview study of aplastic anemia was conducted to evaluate suspected risk factors. Cases (N = 59) newly diagnosed during 1975-82 at 25 Baltimore area hospitals were compared with 59 individually matched (on age, sex and race) controls selected by random digit dialing. The average educational level was less for cases than controls. The major job-related findings were a significant excess for occupational exposure to paint (OR = 6.1; 95% C.I. = 1.2-29.7), further substantiated by a positive dose-response relationship, although painters were not at excess risk. An increased risk of occupational exposure to viruses (OR = 9.0; 95% C.I. = 0.8-105.6) was noted. Additional evidence implicating viral factors included a significant association with prior history of hepatitis (OR = 9.0; 95% C.I. = 1.0, 84.2) and an elevated risk for pre-diagnostic receipt of blood transfusions (OR = 7.1; 95% C.I. = 0.7-68.4). Risks were not increased for other occupational, residential, personal, or medical treatment exposures or for other viral infections, medical conditions, smoking or alcohol consumption prior to diagnosis. Because of the small number of subjects studied and the multiple comparisons examined, these findings should be interpreted cautiously and confirmation should be undertaken in larger, population-based studies.

Adolescent↗
PubMed1989

Baseline characteristics in the Hypertension Prevention Trial. Hypertension Prevention Trial Research Group.

The Hypertension Prevention Trial (HPT) was a randomized, controlled, multicenter (four clinics, four resource centers) trial designed to test the feasibility of achieving and sustaining dietary changes in the intake of calories, sodium, and potassium and to assess the effect of those changes on blood pressure in a normotensive population. The trial involved 841 men and women (plus a test cohort of 78) who, at the first baseline (BL) examination were in the age range of 25-49 years and had diastolic pressure (DBP) greater than or equal to 76 but less than 100 mm Hg (average of two readings), and at the examination prior to randomization (BL 2), had DBP greater than or equal to 78 but less than 90 mm Hg (also averaged). Participants were randomly assigned to a control treatment group (no dietary counseling) or to one of four dietary treatment groups involving counseling designed to reduce calorie intake; reduce sodium intake, reduce sodium and calorie intake, and reduce sodium and increase potassium intake. This chapter presents HPT baseline characteristics by weight stratum, clinic, and treatment group for various demographic, medical history, and nutritional characteristics, for several physiologic variables used in monitoring treatment compliance, and for blood pressure. The degree of comparability observed among treatment groups was within the range expected for the randomization procedure used.

Adult↗
PubMed1989

Familial cancer history and chronic lymphocytic leukemia. A case-control study.

In a population-based case-control study carried out in the Baltimore, Maryland metropolitan area, family cancer history for 342 chronic lymphocytic leukemia cases diagnosed in 1969-1982 revealed significantly higher risks of leukemia as well as other hematolymphoproliferative neoplasms and breast cancer among their first-degree relatives compared with reported occurrence of these neoplasms in first-degree relatives of 342 matched cancer controls and 342 matched controls without cancer. Siblings of case subjects also had a significant elevation of kidney cancer compared with siblings of controls. Only one of the affected case families (and no control family) included more than one additional member with leukemia. The results suggest a genetic component for leukemia occurrence in several case families, although the majority of cases of chronic lymphocytic leukemia appeared to be sporadic. The similarity of findings between the two comparisons (cases vs. cancer controls and cases vs. controls without cancer) diminishes the likelihood of recall bias as an explanation for the observed excess risks.

Adult↗
PubMed1987

Serum protein electrophoresis patterns in chronic lymphocytic leukemia. Clinical and epidemiologic correlations.

Serum protein electrophoresis (SPEP) data obtained at diagnosis were available for 98 of 342 patients with chronic lymphocytic leukemia (CLL) identified in a population-based case-control epidemiologic study. Patients tested with SPEP at diagnosis were significantly younger, more likely to have lymphadenopathy, and more likely to have had their conditions diagnosed at a university hospital than those not tested. Four categories of electrophoretic patterns were identified: normal (N = 56), hypogammaglobulinemia (N = 28), hypergammaglobulinemia (N = 11), and monoclonal gammopathy (N = 3). A higher proportion of those with hypergammaglobulinemia were black, and patients with hypergammaglobulinemia and monoclonal gammopathy were more likely to die within the first year following diagnosis than patients in the other SPEP groups. No association was found, however, between SPEP pattern and a clinical staging classification for CLL. These findings suggest that SPEP may be a useful adjunct in categorizing possible subtypes of CLL and developing future clinical staging classifications.

Agammaglobulinemia↗
PubMed1987

Comparison of methods for determining occupational exposure in a case-control interview study of chronic lymphocytic leukemia.

A comparison was made between two indirect methods for linking reported lifetime occupations and industries of employment with specific exposures and with directly reported exposure information, using data from a population-based case-control interview study of chronic lymphocytic leukemia (CLL). Exposures previously suspected of being associated with CLL were examined using a job-exposure matrix developed by Hoar et al and a linkage between observed occupational exposures and specific occupations, by industry, based on data collected in the National Occupational Hazard Survey (NOHS). In general, concordance on exposure for the two occupation-exposure linkage methods was fairly poor, although it was better for some of the exposures studied (butadiene and asbestos, for which most kappas were between 0.40 and 0.60) than for others (carbon tetrachloride and benzene with kappas ranging from 0.01 to 0.12). Higher proportions of cases and controls directly reported exposure to benzene and asbestos than was determined using the two more indirect methods, neither of which showed consistently greater agreement with direct reporting.

Epidemiologic Methods↗
PubMed1986

Chronic lymphocytic leukemia and acquired disorders affecting the immune system: a case-control study.

The relationship of a number of subacute or chronic infectious diseases, connective tissue or autoimmune disorders, allergic conditions, and surgical excision of lymphoid tissue with chronic lymphocytic leukemia (CLL) was examined in a case-control study involving 342 cases and 342 matched controls. In both analyses of all matched pairs and those pairs in which both subjects were respondents, no statistically significant association was found between a history of subacute viral infections or subacute and chronic bacterial infections and CLL. Connective tissue or autoimmune disorders also were found not to be associated with CLL. Examination of the association between several allergic conditions and CLL suggested a protective effect as did a "dose-response" analysis, although none of the individual disorders showed a statistically significant relationship; however, a test for linear trend was significant (P = .04). Similarly, examination of the relationship between surgical excision of lymphoid tissue in several anatomic locations and CLL showed a protective effect, statistically significant for tonsillectomy-adenoidectomy (odds ratio = 0.69; 95% confidence interval = 0.48, 0.98). A statistically significant negative dose-response relationship, substantiating the protectiveness of the effect, was found.

Aged↗