Biomedical subjects

L S Magder

Publications and source records attributed to L S Magder.

32 records · Page 2Linked to original sources

PubMed1997

Logistic regression when the outcome is measured with uncertainty.

In epidemiologic research, logistic regression is often used to estimate the odds of some outcome of interest as a function of predictors. However, in some datasets, the outcome of interest is measured with imperfect sensitivity and specificity. It is well known that the misclassification induced by such an imperfect diagnostic test will lead to biased estimates of the odds ratios and their variances. In this paper, the authors show that when the sensitivity and specificity of a diagnostic test are known, it is straightforward to incorporate this information into the fitting of logistic regression models. An EM algorithm that produces unbiased estimates of the odds ratios and their variances is described. The resulting odds ratio estimates tend to be farther from the null but have greater variance than estimates found by ignoring the imperfections of the test. The method can be extended to the situation where the sensitivity and specificity differ for different study subjects, i.e., nondifferential misclassification. The method is useful even when the sensitivity and specificity are not known, as a way to see the degree to which various assumptions about sensitivity and specificity affect one's estimates. The method can also be used to estimate sensitivity and specificity under certain assumptions or when a validation subsample is available. Several examples are provided to compare the results of this method with those obtained by standard logistic regression. A SAS macro that implements the method is available on the World Wide Web at http:@som1.ab.umd.edu/Epidemiology/software.h tml.

Adult↗

PubMed1997

Evaluation of 14- and 11-gauge directional, vacuum-assisted biopsy probes and 14-gauge biopsy guns in a breast parenchymal model.

PURPOSE: To compare commercially available 14-guage core biopsy guns and 11- and 14-gauge, directional, vaccum-assisted biopsy probes for tissue yield and fragmentation. MATERIALS AND METHODS: One hundred passes were made through fresh turkey breasts by using each of 11 14-gauge, automated biopsy gun-needle combinations and a directional, stereotactic, vacuum-assisted biopsy system equipped with 11- or 14-gauge probes. Specimens were measured for total weight, individual length, diameter, and number of fragments. RESULTS: Among the handheld devices, the Pro-Mag 2.2 gun (Manan Medical Products, Northbrook, Ill) and 14-gauge Biopsy-Cut needle (Bard, Covington, Ga) had the greatest yield (17.7 mg per core specimen); this combination also produced the greatest percentage of nonfragmented cores (83%). Directional, vacuum-assisted biopsy specimens were significantly larger (P < .001): 36.8 mg per core specimen for the 14-gauge probe and 94.4 mg per core specimen for the 11-gauge probe. Specimens obtained with directional, vacuum-assisted biopsy were more fragmented than those obtained with spring-actuated, two-stage, long-throw, automated biopsy systems. CONCLUSION: Statistically significant differences with various biopsy devices are seen in the breast tissue yield and in fragmentation.

Adult↗

PubMed1997

Methylphenidate patterns among Medicaid youths.

Treatment of attentional disorders in America has increased dramatically in recent years. This trend is accounted for partly by lengthening the duration of treatment into adulthood for some individuals as well as by increased treatment among girls. Beyond these factors, the role of economic status, race, and geographic region to explain the variation in methylphenidate use is not well understood. Computerized administrative data were used to explore the influence of several sociodemographic factors on the prevalence of methylphenidate use. The data source consisted of Maryland Medicaid prescription drug reimbursement claims data for FY1991 for children ages 5 to 14 years. In effect, the study was restricted to a sample of patients with limited income. The study aims included (1) measuring gender-, age-, race-, and region-specific methylphenidate prevalence for this restricted income population; (2) comparing the Caucasian:African-American (C:A-A) ratio for methylphenidate with the C:A-A ratio for several drug therapies having non-psychotropic uses, specifically the anti-asthma drug, theophylline, and antibiotics for infections; and (3) estimating the average daily dose of methylphenidate from prescription claims data. Total drug-specific prevalence among the 5-14 year olds was 2.2 percent for methylphenidate while age-specific prevalence varied from 0.4 percent (5 year olds) to 3.4 percent (9 year olds). The gender ratio was 3.7:1 (M:F), confirming the increasing trend for girls to receive this medication. Substantial variation across eight defined regions of the state was observed. Racial differences were pronounced: African-Americans were 2.5 times less likely to receive methylphenidate than Caucasian youths. As hypothesized, non-psychotropic drug use was distinctly different from psychotropic drug use in terms of race: theophylline was 1.5 times more likely to be found for African-Americans than Caucasians, whereas antibiotic prescriptions were 1.5 times more likely to be prescribed to Caucasian youths. Average daily dose of methylphenidate was estimated to be 18.7 +/- 10.4 mg for 5-9 year olds and 26.8 +/- 14.0 mg for 10-14 year olds. This brief report confirms the typically lower rate among African-American Medicaid youths for most prescription drugs. The dramatic racial disparity for the psychotropic agent methylphenidate is a new and compelling finding which should be verified among other economic groups. Diagnostic, referral, and cultural bias should be ruled out as possible explanations for the observed differences.

Adolescent↗

PubMed1996

Large-core biopsy guns: comparison for yield of breast tissue.

PURPOSE: To compare seven large-core, long-throw, 14-gauge biopsy guns for yield and quality of breast tissue obtained. MATERIALS AND METHODS: A two-phase, randomized and blinded study was performed. In the first phase, four fully automated 14-gauge biopsy guns (BIP, Manan, Biopsy, and ASAP) and one semiautomated device (Temno) were used to obtain breast cores from a cadaver. Samples were assessed for volume, number of fragments, and crush artifact. In the second phase, seven biopsy guns (previously mentioned guns plus Monopty and Ultra-Cut guns) were used to obtain cores from a breast parenchyma model. These cores were then evaluated for weight, volume, and number of fragments. RESULTS: The mean specimen volume of cadaveric breast tissue obtained was 17.9 mm3 for the BIP gun, 17.8 for the Manan gun, 14.9 for the Biopsy gun, 14.1 for the ASAP gun, and 9.9 for the Temno gun. The Temno gun obtained statistically significantly smaller volumes than all other guns. For the breast parenchyma model, mean obtained volumes were 24.5, 24.1, 16.2, 21.7, 17.5, 20.0, and 15.2 mm3, respectively. The BIP and Manan guns yielded statistically significantly larger cores than all other guns except the ASAP. CONCLUSION: Yields of breast tissue provided by each biopsy device differed statistically significantly. BIP and Manan biopsy guns yielded the greatest volume of core tissue, which may facilitate histopathologic diagnosis from breast biopsies performed with imaging guidance.

Animals↗

PubMed1990

Effect of patient characteristics on performance of an enzyme immunoassay for detecting cervical Chlamydia trachomatis infection.

We compared the performance of a commercial enzyme immunoassay (EIA) (Chlamydiazyme; Abbott Diagnostics, North Chicago, Ill.) with that of cell culture for the detection of Chlamydia trachomatis cervical infection in 1,417 women attending public health clinics. Confirmatory chlamydial testing by a direct fluorescent-antibody test (MicroTrak; Syva Co., Palo Alto, Calif.) was performed on specimens from women who had positive EIAs. Overall, only 57% of women who had a positive chlamydial test by cell culture were also positive by EIA. We noted a strong association between the number of chlamydial inclusions in cell culture and a positive EIA outcome. The proportion of culture-positive women who also had a positive EIA declined with age and a history of previous sexually transmitted disease and increased among oral contraceptive users. The results of direct fluorescent-antibody confirmatory testing suggested that cell culture was also insensitive for the detection of C. trachomatis infection. Our observations demonstrate that the performance of the chlamydial EIA may vary greatly with individual patient characteristics and that the utility of EIA as a screening test may be limited, especially in older women.

Adult↗

PubMed1989

A seroepidemiologic survey of the prevalence of herpes simplex virus type 2 infection in the United States.

The prevalence of infection with the genital herpes simplex virus type 2 (HSV-2) has been difficult to ascertain, primarily because of the large percentage of subclinical cases and the limitations in specificity of serologic assays for antibody to HSV-2. To obtain an improved estimate of the distribution of HSV-2 infection in the United States, we used an HSV type-specific antibody assay to test serum samples from 4201 participants in the second National Health and Nutrition Examination Survey. The results in our sample indicate that in the period from 1976 to 1980, 16.4 percent of the U.S. population 15 to 74 years of age (approximately 25 million persons) was infected with HSV-2 (95 percent confidence interval, 14.2 to 18.6 percent). Age and race were the demographic factors associated most strongly with the presence of HSV-2 antibody. The prevalence of the antibody increased from less than 1 percent in the group under 15 years old to 20.2 percent in the group 30 to 44 years old; it increased only slightly thereafter. In the oldest group, 60 to 74 years of age, the prevalence was 19.7 percent in whites and 64.7 percent in blacks. Among blacks of all age groups, but not whites, higher rates were observed in women than in men. The associations were weaker with respect to marital status, income, education, urban residence, and region of the country. After control for age, sex, and race, only the association with marital status remained significant; the rate was increased in persons previously married--i.e., divorced, separated, or widowed. We conclude that the prevalence of HSV-2 infection in the United States is higher than has previously been recognized and that many infections with this sexually transmitted virus may be subclinical.

Adolescent↗

PubMed1989

Race and the prevalence of syphilis seroreactivity in the United States population: a national sero-epidemiologic study.

We used the 1978 National Health and Nutrition Examination Survey to examine the prevalence of positive syphilis serologies in the US population. Analysis of risk markers--gender, age, marital status, education, income, and residence--indicates that all except gender are associated with syphilis seroreactivity, independent of race. Controlling for associated risk markers, the Black-White odds ratio of syphilis seroreactivity is 4.7 (95% CI = 2.7, 8.2). Current knowledge of racial differences in sexual and health care behavior does not explain the Black-White difference in the prevalence of syphilis seroreactivity.

Adolescent↗

PubMed1988

Factors related to genital Chlamydia trachomatis and its diagnosis by culture in a sexually transmitted disease clinic.

The authors cultured 2,320 patients who attended the Denver Metro Health Clinic for Sexually Transmitted Diseases from September 1981 to June 1983 to determine clinical and epidemiologic factors associated with genital chlamydial infection. Among consecutive heterosexual men with urethral discharge, 226 of 849 (27%) had positive urethral cultures, with rates significantly lower among those with profuse (18%) or purulent (19%) discharges, and higher (37%) among those with symptoms for more than seven days. In a subgroup of men without gonococci, those who had polymorphonuclear leukocytes on smear had higher isolation rates (33%) than those who did not (3%). Among consecutive female patients, 172 of 1,031 (17%) had positive cervical cultures, with rates significantly lower in those who were white (13%), married (7%), or using a diaphragm (0 of 77), and higher in those who were positive for Neisseria gonorrhoeae (38%). There was a marginally significant increased rate of chlamydial isolation among oral contraceptive users only for women aged 20 years or younger. Younger age was significantly associated with chlamydial isolation in both men and women after controlling for sexual activity and other factors. Various patient characteristics can be combined to define subgroups of men and women, with rates of isolation ranging from under 4% to over 60%. These results can be useful in deciding whom to test and whom to treat presumptively in a public health setting.

Adult↗

PubMed1986

Primary prevention of sexually transmitted diseases. A primer for clinicians.

With the advent of sexually transmitted infections for which curative therapy is not available, primary prevention has assumed greater importance. The spectrum of sexually transmitted diseases (STDs) has broadened, and clinicians need to understand the mechanisms of their transmission and prevention. Modifying selection of sexual partners and avoiding certain sexual practices should theoretically reduce the risk of infection. Clinical and laboratory studies indicate that the use of condoms, diaphragms, and spermicides reduces the risk of acquiring certain infections. At present, hepatitis B is the only STD for which a safe, effective vaccine is available. Use of oral antibiotics cannot be recommended. Postcoital washing or urination have not been shown to have a protective effect against infection. Because of the potential benefits, persons at risk for STDs should be encouraged to modify their sexual behavior and use barrier methods and spermicides to protect themselves against sexually transmitted infections.

Administration, Oral↗

PubMed1986

Acute Chlamydia trachomatis respiratory infection in childhood. Serologic evidence.

Serum samples from 184 infants and children whose blood was drawn during a clinic visit were tested for antibody to Chlamydia trachomatis, Epstein-Barr virus, and cytomegalovirus. Lifetime illness history was obtained from clinic records. Fifteen percent had anti-C trachomatis IgM antibody. Anti-C trachomatis IgM without IgG was significantly associated with upper respiratory tract syndromes within the 14 days prior to phlebotomy in 6- to 10-year-old patients. This association was not due to polyclonal activation from Epstein-Barr virus infection. A definitive study of chlamydial illness in children rather than infants appears to be indicated.

Acute Disease↗

PubMed1986

Personal protection against sexually transmitted diseases.

Primary prevention of sexually transmitted diseases has received little emphasis in control programs. To evaluate the effectiveness of prevention strategies, we reviewed the world's literature on this topic. Use of condoms and spermicides greatly reduces the risk of gonorrhea, and barrier methods are practical and acceptable. Certain systemic antibiotics are effective, but for practical reasons, their use cannot be recommended. Washing or urinating after sexual exposure does not appear to protect against infection. Although the effectiveness of modifying sexual behavior to reduce the risk of sexually transmitted diseases has not been evaluated, many people have changed or are willing to change their behavior. Even if preventive measures are used consistently by only a minority of persons at risk, rates of sexually transmitted diseases would decline rapidly. In this era of sexually transmitted diseases that are not readily cured by antibiotics, use of effective preventive measures should be strongly encouraged.

Anti-Bacterial Agents↗

PubMedDate not supplied

Isocaloric glutamine-free diet and the morphology and function of rat small intestine.

BACKGROUND: The importance of L-glutamine as metabolic fuel for enterocytes and its role in prevention of mucosal atrophy during total parenteral nutrition is well documented. No data are available to date that document whether a glutamine-free complete enteral diet, requiring full energy expenditure for hydrolysis and absorption, is associated with changes in the morphology and function of the small intestine. Our aim was to examine the effect of such a diet during a 4-week period on the morphology and function of the small intestine of rats. METHODS: Three isocaloric solid rat food, containing 0%, 4%, and 8% of glutamate, respectively, were fed to three groups of rats. On the 7th and 28th days the morphology of the jejunum, the subcellular structure of enterocytes on transmission electron microscopy, enzyme activities, blood, and muscle glutamine were examined and compared in the three groups. RESULTS: The rats on the glutamine-free diet had significantly lower mucosal wet weight, protein and DNA content, and number of intraepithelial lymphocytes on the 7th day, whereas the number of mitoses in the Lieberkuhn's crypts was significantly less on the 28th day. The height of the enterocytes and villi was 20% higher on average in the glutamine-free group. Electron microscopy revealed either early (swelling of cristae) or terminal (swelling of matrix) mitochondrial degenerative changes, homogenization of apical cytoplasm, and degeneration and fragmentation of microvilli with loss of their rootlets. The Na+, K(+)-ATPase activity was markedly decreased in the glutamine-free group compared with that of the other groups, most likely because of a diminished energy supply. Among brush border membrane enzymes, lactase activity decreased markedly (p < .05) in the first week. The glutamine-free diet resulted in an increase of the lung glutamine synthetase activity and decrease in muscle glutamine content by the 28th day of the diet. CONCLUSIONS: Our study shows for the first time that a complete enteral diet, deficient only in glutamine, is associated with significant early morphologic and functional changes in the small intestine. The precise effect on intracellular events and the time of onset of these changes needs to be clarified in the future.

Animals↗

PubMedDate not supplied

Condom use with regular and casual partners among women attending family planning clinics.

A survey of 16,632 women attending family planning clinics in Pennsylvania found that only 13 percent of the sample used condoms. Moreover, 67 percent of the women with regular partners never used condoms with those partners, and 72 percent of women who had casual partners never used them with those partners. Levels of condom use with both regular and casual partners were higher among women younger than 20, those who were nonwhite, those with multiple partners and those who reported a previous STD infection. However, women who had sex partners who used intravenous drugs were less likely to use condoms with regular or casual partners than were women who did not have drug-using partners.

Acquired Immunodeficiency Syndrome↗

PubMedDate not supplied

Risk behaviors for HIV infection in clients of Pennsylvania family planning clinics.

Responses from a statewide survey of risk behaviors among clients of Planned Parenthood clinics in Pennsylvania indicate that a sizable proportion of these women are at intermediate or high risk for exposure to the human immunodeficiency virus (HIV). Overall, nearly five percent of the 15,499 women in the sample reported personal behavior, or a partner's behavior, that placed them at high risk, while an additional 20 percent were at intermediate risk. Among all women surveyed, 13 percent had had three or more partners in the past year, 12 percent had had a sexually transmitted disease, four percent had partners who were intravenous (IV) drug users, two percent were either current or past IV drug users, one percent had bisexual partners and less than one percent had partners who had hemophilia or who were infected with the AIDS virus.

Adolescent↗