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Biomedical subjects

M T Schechter

Publications and source records attributed to M T Schechter.

At least 163 records · Page 9Linked to original sources
PubMed1990

Underreporting of AIDS cases in Canada: a record linkage study.

To estimate the rate of underreporting of AIDS (acquired immune deficiency syndrome) to the Federal Centre for AIDS (FCA), in 1988 the initials, date of birth and place of residence of 66 patients with AIDS known to the Toronto Sexual Contact Study (TSCS), 65 patients with AIDS known to the Vancouver Lymphadenopathy-AIDS Study (VLAS) and other participants in both studies who did not have AIDS were sent to the Bureau of Epidemiology and Surveillance, FCA. The FCA conducted a manual record linkage to link these data to the national registry of reported cases. The rate of underreporting was 12% (8/65) for the VLAS and 18% (12/66) for the TSCS. The specific diagnosis was not related to the rate of underreporting. For the TSCS the rate of underreporting had increased from 0% in 1983-84 to 44% in 1987-88 (p = 0.001). Differences in the observed rates of underreporting between the two studies are likely the result of differences in the reporting responsibilities of physicians involved in the studies.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Susceptibility to AIDS progression appears early in HIV infection.

To investigate whether predictors of AIDS progression are operative very early in the natural history of HIV infection, we conducted a nested case-control study within a cohort of 119 subjects who seroconverted while under observation in a prospective study of homosexual men. For each of the 18 cases who have progressed to AIDS, we randomly selected three controls who had seroconverted within 3 months of the case but who have remained AIDS-free. Cases and controls were compared with regard to laboratory and clinical parameters obtained at the time of the earliest HIV-positive result. The median duration between the estimated date of seroconversion and this first positive result was 4 months for cases and 6 months for controls. Cases exhibited lower CD4 counts (657 versus 774 x 10(6)/l; P = 0.037), lower CD4: CD8 ratios (0.98 versus 1.39; P = 0.003), higher immune complex levels (C1q binding: 25 versus 15%; P = 0.002), lower hemaglobin concentrations (14.8 versus 15.2 g/l; P = 0.011), higher immunoglobulin (Ig) A levels (272 versus 184 mg/dl; P = 0.003), and higher IgG levels (1530 versus 1300 mg/dl; P = 0.037) than controls. Cases exhibited higher CD8 counts of marginal statistical significance (732 versus 597 x 10(6)/l; P = 0.059). No differences were observed with respect to IgM levels, total lymphocyte or white blood cell counts, or the frequency of generalized lymphadenopathy. A total of 27.8% of cases but only 11.5% of controls reported one or more symptoms during the 6-month period preceding the first positive visit (P = 0.027). We conclude that laboratory and clinical abnormalities which are predictive of more rapid progression to AIDS may appear very early in HIV infection. This suggests that some of the factors responsible for more rapid disease progression are present in the host prior to or shortly after infection occurs.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Preliminary evaluation of a scheme for grading the gross morphology of the human intervertebral disc.

A five-category grading scheme for assessing the gross morphology of midsagittal sections of the human lumbar intervetebral disc was developed. The ability of three observers to categorize a series of 68 discs with a wide spectrum of morphologies established the comprehensiveness of the classification. Three independent observers tested the reproducibility of the procedure by assignment of grades blindly to duplicate images of 68 discs taken from 15 spines. The intraobserver agreement ranged from 87 to 91%. The interobserver agreement was 61, 64, and 88% for the three pairs, the two low values being attributable to the bias of one observer. The agreement between the assigned and average grades was 85, 92, 68, 90, and 76% for Grades I through V, respectively. Except for Grade III, the disagreements were attributable mainly to the bias of one observer. Both the increase in the grade with age and the finding that all the discs within 14 of 15 spines had a narrow range of grades demonstrated the biologic credibility of the scheme.

Adult↗
PubMed1990

Retinopathy of prematurity-induced blindness: birth weight-specific survival and the new epidemic.

A recent population-based study in the Canadian province of British Columbia showed that, since the mid-1960s, there has been a significant increase in the incidence of retinopathy of prematurity-induced blindness in infants weighing 750 to 999 g at birth. To determine the impact of changing birth weight-specific survival on this new epidemic, all infants born in the province in the period 1952 through 1986 and known to the British Columbia Health Surveillance Registry as having retinopathy of prematurity-induced blindness were identified. In addition, the birth registration records for the 1,299 740 infants born in British Columbia in the same period and the death records of the 22,940 British Columbia-born infants who died in the province before the end of their first year of life were linked using a combination of probabilistic and manual record linkage techniques. These linked records and the records from the Health Surveillance Registry were used to calculate birth weight-specific incidence rates of retinopathy of prematurity-induced blindness in liveborn infants and first-year-of-life survivors. The rates, in 5-year intervals, showed that, in both liveborn infants and first-year survivors, the highest birth weight-specific rates occurred during the first epidemic of retinopathy of prematurity, which ended in British Columbia in 1954. Since the mid-to late-1960s, the incidence of retinopathy of prematurity-induced blindness in liveborn infants weighing less than 1000 g increased steadily whereas in infants weighting 1000 to 1499 g, incidence decreased slightly since the original epidemic ended. However, the experience of first-year-of-life survivors is substantially different.(ABSTRACT TRUNCATED AT 250 WORDS)

Birth Weight↗
PubMed1990

Risk factors for Kaposi's sarcoma in the Vancouver Lymphadenopathy-AIDS Study.

In our ongoing cohort study of homosexual men, the ratio of new Kaposi's sarcoma (KS) cases to new opportunistic infections (OI) during the periods 1982-1985, 1986-1987, and 1988-1989 fell from 0.75 (9 KS: 12 OI) to 0.57 (12 KS:21 OI) to 0.27 (4 KS:15 OI), respectively. To examine factors associated with the development of KS as compared to OI, we compared antecedent risk factors in 25 KS cases and 48 OI "controls." In univariate analyses, several classical HIV risk factors including numbers of sexual partners and receptive anal intercourse were higher in the KS than the OI group. The strongest associations were found with an elevated number of sex partners in high-risk areas (San Francisco, Los Angeles, and New York) in the 5 years prior to enrollment and with elevated use of nitrite inhalants. Logistic regression revealed the latter two variables and an elevated number of partners contacted in washrooms/parks to be significant, independent risk factors for KS relative to OI. Any or all of these variables could be related with early HIV infection. However, the association with early sexual contact in high-risk areas raises the more intriguing possibility that this variable is an indicator of an increased exposure either to a particular strain of HIV that is more pathogenic for KS, or, more likely, to a sexually transmitted KS cofactor that may have been more highly concentrated in these areas at this early point in the epidemic. The present study supports an independent association with use of nitrite inhalants, which could be hypothesized either to have an independent biologic effect on KS or to enhance the efficiency of transmission of the cofactor virus.

Acquired Immunodeficiency Syndrome↗
PubMed1989

A trial of desmopressin (1-desamino-8-D-arginine vasopressin) to reduce blood loss in uncomplicated cardiac surgery.

Previous studies have suggested that desmopressin may reduce the bleeding diathesis that often complicates open-heart surgery. To pursue this question further, we performed a double-blind, randomized, placebo-controlled trial to determine whether the previously reported beneficial effect of desmopressin on hemostasis during complex cardiac surgery was applicable to all elective cardiac surgical procedures involving cardiopulmonary bypass. In 150 consecutive patients, most of whom underwent primary coronary-artery bypass grafting, we compared the effects of intravenous desmopressin (0.3 microgram per kilogram of body weight) with those of saline placebo on postoperative blood loss and the need to replace blood products. The median amount of blood lost within the first 24 hours after operation was similar in the desmopressin and placebo groups (865 vs. 738 ml; P = 0.26). The postoperative use of blood replacement products did not differ significantly between the groups (1025 ml [95 percent confidence interval, 300 to 4140 ml] in the desmopressin group and 860 ml [247 to 5346 ml] in the placebo group). Desmopressin is believed to exert its hemostatic effect by releasing von Willebrand factor. The level of ristocetin cofactor, a functional index of the level of von Willebrand factor, was increased approximately twofold from base line in both treatment groups 90 minutes and 24 hours after the administration of medication. Similarly, the levels of von Willebrand factor multimers increased uniformly in both groups. These findings may be consistent with a normal stress response of von Willebrand factor to major surgery and could explain our failure to detect a therapeutic effect of desmopressin. We conclude that the majority of patients who undergo elective cardiac surgery receive no hemostatic benefit from the use of desmopressin.

Adult↗
PubMed1989

Chronic exposure to sour gas emissions: meeting a community concern with epidemiologic evidence.

For 25 years residents of a rural area in southwestern Alberta have complained of health problems attributed to sour gas emissions from nearby natural gas refineries. We undertook a large epidemiologic study of the current health status and the selected morbidity rates among 2152 people in the exposed area. We established two comparison groups: one was a demographically similar unexposed population and the other a demographically different group also exposed to sour gas emissions in another region. The methods included a cross-sectional survey of current residents and separate historical cohort studies involving registry linkage to investigate cancer incidence and all-cause mortality. The cross-sectional survey involved a comprehensive health questionnaire, standardized clinical examinations by physicians blinded to the subjects' symptoms and concerns, and several laboratory tests. We were able to contact just under 60% of the people who we knew had moved from each area since 1958 and found no evidence of selective migration for health reasons. Although the residents of the exposed area reported an excess number of symptoms and health problems there were no significant differences in the mortality rate, incidence of cancer, reproductive problems, major ailments, hair levels of arsenic and certain metals or respiratory function between the groups.

Adolescent↗
PubMed1989

Practice patterns of family physicians with 2-year residency v. 1-year internship training: do both roads lead to Rome?

Are there differences in patterns of practice between actively practising physicians who have been certified after a 2-year family practice residency and matched physicians without certification who have completed the standard 1-year internship? With the use of billing files prepared by the British Columbia Medical Association a group of 65 family practice certificants in active practice in British Columbia was compared with a control group of 130 internship trainees matched by year and school of graduation, category of billing (i.e., solo or group) and region. A wide range of practice features was assessed for the fiscal years 1984-85, 1985-86 and 1986-87. No differences were detected between the groups in 1986-87 for the following practice variables: number of patients (1888 and 1842 respectively), number of personal services billed for (7265 and 7173), number of personal services per patient (3.9), amount of funding for personal services ($140,192 and $140,100) and amount per patient for personal services ($77 and $79). Age-adjusted costs for male and female patients were similar in the two groups. Of six services thought to be influenced by type of training, only maternity care generated a significantly higher number of billings in the study group (341 v. 249). These results suggest that there is no demonstrable effect of training on patterns of practice. However, the question of the effect of training on quality of care and whether the 2-year residency may have a longer effect on practice patterns should be the focus of future research.

Accounting↗
PubMed1989

Cigarette smoking and breast cancer: case-control studies of prevalent and incident cancer in the Canadian National Breast Screening Study.

Two case-control studies of Canadian women aged 40-59 years are reported investigating the relation of cigarette smoking with initial visit (prevalent) and subsequent visit (incident) breast cancer detection, respectively, within the Canadian National Breast Screening Study. The analysis of prevalent breast cancer (1982-1985), which involved 254 cases and 762 controls, showed no evidence of an elevated risk for women with a history of cigarette smoking, with odds ratios of 0.9 (95% confidence interval (Cl) 0.6-1.5) and 1.2 (95% Cl 0.8-1.8) in premenopausal and postmenopausal subjects, respectively. Similarly, in the incident breast cancer analysis (1981-1987) based on 317 cases and 951 controls, women with a history of cigarette smoking had odds ratios of 1.2 (95% Cl 0.8-2.0) and 1.2 (95% Cl 0.9-1.7) in the premenopausal and postmenopausal categories, respectively. No evidence of dose response or of elevated risk in ex-smokers or current smokers was found in either study. These results persisted despite adjustment for several important variables. The present data demonstrate no association between smoking and prevalent or incident breast cancer in either menopausal category, contradicting the authors' previous finding of a positive association with premenopausal prevalent disease earlier in this screening study. The relation of smoking and breast cancer remains controversial. Further study is required to determine whether an association truly does not exist or whether smoking might have both protective and harmful effects that are mediated through different pathways, thus accounting for the paradoxical findings in the literature to date.

Adult↗
PubMed1989

Progression to AIDS and predictors of AIDS in seroprevalent and seroincident cohorts of homosexual men.

As part of an ongoing prospective study of seropositive homosexual men in Vancouver, Canada, a seroprevalent cohort of 246 subjects (i.e. duration of infection unknown) and a seroincident cohort of 102 subjects (i.e. duration of infection known) were followed a median of 63 and 45 months, respectively. Follow-up with validation utilizing record linkage with the Canadian Federal Centre for AIDS registry revealed 58 and nine cases of AIDS in the seroprevalent and seroincident cohorts, respectively, through July 1988. These data yield product limit estimates of the cumulative progression rates to AIDS at 60 months of 23.0% for the seroprevalent cohort, 13.0% for the seroincident cohort, and 21.0% for the combined groups. Univariate analyses revealed the following to be statistically and clinically significant predictors of AIDS progression: low CD4 counts, low CD4/CD8 ratios, elevated immune complexes, elevated immunoglobulin G (IgG) and immunoglobulin A (IgA) levels, and low platelet counts. Cox regression revealed that elevated IgA levels, low CD4 counts, elevated immune complexes, two or more symptoms, and more than 20 male sexual partners in high-risk areas in the 5 years prior to enrollment were independent predictors of progression to AIDS over the subsequent 5 years. A multivariate risk function based on the latter five variables delineated low-, medium- and high-risk groups whose 5-year progression rates to AIDS were 6.7, 15.6 and 64.4%, respectively. The high-risk group contained 75% of all subjects who progressed to AIDS. Only 6% of the high-risk group would have qualified for zidovudine therapy under current guidelines at the beginning of the observation period.(ABSTRACT TRUNCATED AT 250 WORDS)

Acquired Immunodeficiency Syndrome↗
PubMed1989

Respiratory health of a population living downwind from natural gas refineries.

Since 1958 there has been a perception of excess illness in a rural Canadian population living downwind from two natural gas refineries, the emissions of which contain mostly sulfur dioxide but also hydrogen sulfide. To determine if there was an excess of adverse health outcomes in the population exposed (defined by place of residence), a health survey was undertaken in 1985 in this area and in one unexposed to emissions but demographically similar. Participation was 92% from both the exposed population (n = 2,157) and a representative sample (n = 839) of the main reference population. More respiratory symptoms were reported in the exposed group than in the non-exposed group among those 5 to 13 yrs of age (28% versus 18%) and among never-smokers greater than or equal to 14 yrs of age (35% versus 24%). FEV1, FVC, and FEV1/FVC were similar in both areas. Dichotomizing the level of exposure (high, low) within the exposed area revealed a trend in the high exposure area toward increased respiratory symptoms in the younger age group (39% versus 24%), but decreased symptoms in the older age group (33% versus 36% among never-smokers). FEV1 was similar between the two areas. The excess of respiratory symptoms in the exposed area unassociated with impaired spirometric values would be compatible with increased awareness of health or a small biologic environmental effect.

Child↗
PubMed1989

The influence of psychological status on respiratory symptom reporting.

The American Thoracic Society respiratory symptom questionnaire (ATS-Q) is widely used and has provided valuable information in epidemiologic studies. To determine the influence of psychological status on respiratory symptoms, we compared subjects' ATS-Q responses to their Ilfeld Psychiatric Symptom Index (PSI) scores. To minimize the potential confounding effect of respiratory disease on the association between respiratory and psychological status, from a population-based survey of 3,628 subjects, we studied only the 600 "healthy" subjects, defined by the following characteristics: between 14 and 55 yr of age; never-smokers; no diagnoses of respiratory, heart, kidney, thyroid disease, or anemia; and normal spirometry (defined as an FEV1 and FVC greater than 80% of predicted). Associations were found between respiratory symptoms (cough, phlegm, wheeze, dyspnea) and PSI subscales (anxiety, anger, depression, and cognitive disturbance). Adjusted odds ratios for respiratory symptoms ranged from 1.13 to 2.15 for every 10% increase in PSI score. Psychological status is an important determinant of respiratory symptoms and therefore must be taken into consideration when interpreting results of epidemiologic studies using questionnaire information.

Adolescent↗
PubMed1989

Cancer downwind from sour gas refineries: the perception and the reality of an epidemic.

A rural population in southwestern Alberta, Canada, living downwind from natural gas refineries, has expressed concerns about an excess of adverse health outcomes over the last 25 years. This has escalated to the point of causing a prominent sociopolitical controversy within the province. As part of a large field epidemiologic study undertaken during the summer of 1985 to investigate possible health effects, a residential cohort study was carried out to study cancer incidence. The cohort was defined as all those individuals who resided in the area in 1970. A total of 30,175 person-years of risk within Alberta were experienced by this cohort from 1970 to 1984. The incident cancers during this period were enumerated by computerized record linkage with the Alberta Cancer Registry. Age- and sex-standardized incidence ratios, based on expected rates from three prespecified demographically similar, nonmetropolitan Southern Alberta populations, were 1.05, 1.09, and 1.03, respectively, none of which was significantly different from unity. Although they do not address the issue of etiologic association, these data can provide considerable reassurance to a community that was convinced it had experienced an epidemic of cancer.

Acid Rain↗
PubMed1989

The role of secondary vaccine failures in measles outbreaks.

An outbreak of measles in 1985-86 in a community where measles vaccine trials had been carried out from 1974-76 allowed the assessment of the role of secondary vaccine failures in previously immunized children. A total of 188 children from the vaccine trial were followed. Of these, 175 seroconverted initially while 13 (6 per cent) required re-immunization (primary failure). A total of 13 cases of measles, eight of which were laboratory and/or physician-confirmed, were reported in this cohort. Of these, nine cases occurred in the 175 subjects who had hemagglutination inhibition test (HI) and neutralizing antibody responses following the initial immunization. These nine cases represent secondary vaccine failures. An additional four cases occurred in the 13 subjects with primary vaccine failure. We conclude that secondary vaccine failures occur and that while primary failures account for most cases, secondary vaccine failures contribute to the occurrence of measles cases in an epidemic. A booster dose of measles vaccine may be necessary to reduce susceptibility to a sufficiently low level to allow the goal of measles elimination to be achieved.

Adolescent↗