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Biomedical subjects

R W Ryder

Publications and source records attributed to R W Ryder.

At least 55 records · Page 3Linked to original sources
PubMed1990

Heterosexual transmission of HIV-1 among employees and their spouses at two large businesses in Zaire.

To better understand the reasons why up to 80% of all HIV-1 infections in Zaire, but less than 5% in North America and Europe, are acquired through heterosexual transmission, and to assess the impact of HIV-1 infection on a large urban African workforce, we enrolled 7068 male employees, 416 female employees and 4548 female spouses of employees at two large Kinshasa businesses (a textile factory and a commercial bank) in a prospective study of HIV-1 infection. The HIV-1 seroprevalence rate was higher in male employees (5.8%) and their spouses (5.7%) at the bank than among male employees (2.8%) and their spouses (3.3%) at the textile factory. At both businesses HIV-1 seroprevalence was higher among employees in managerial positions (5.0%) than among workers in lower-level positions (3.0%; P less than 0.0001). In a multivariate analysis of male employees, receipt of a transfusion, a history of genital ulcer disease, working at the bank, urethritis, or being divorced or separated were independently associated with HIV-1 infection. During 1987 and 1988, AIDS was the most common cause of death among recently employed workers, accounting for 20 and 24% of all deaths at the textile factory and the commercial bank, respectively. The HIV-1 seroprevalence rate was higher among female workers (7.7%) than among the spouses of male workers (3.9%; P = 0.001). In multivariate analysis of the wives of workers, having an HIV-1-seropositive spouse, receipt of a blood transfusion, or a history of genital ulcer disease were independently associated with HIV-1 infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Acquired Immunodeficiency Syndrome↗
PubMed1990

Successful use of pooled sera to determine HIV-1 seroprevalence in Zaire with development of cost-efficiency models.

To determine the accuracy and cost efficiency of pooling sera prior to HIV-1 testing, sera from 8,000 Kinshasa factory workers and their spouses were screened individually (2.44% seropositive) and in 800 pools of 10 sera each. There were no false-negative or false-positive pools, resulting in a calculated seroprevalence estimate of 2.42%. Further testing of all sera in positive pools can identify HIV-positive individuals. These applications were modeled to compare the cost-efficiency of pooling with individual testing under different conditions. The results suggest that pooling provides an alternative test format for use in both developing and industrialized countries when the seroprevalence and/or the marginal cost of obtaining a sample are sufficiently low. For our cohort, testing only the pools for seroprevalence estimation resulted in a 78% cost saving compared with individual testing; pooling with subsequent identification of individual seropositives represented a 56% cost reduction.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Performance and cost-effectiveness of a dual rapid assay system for screening and confirmation of human immunodeficiency virus type 1 seropositivity.

Recent studies have shown that rapid, instrument-free assays for the detection of antibody to human immunodeficiency virus (HIV) can be as sensitive and specific as enzyme-linked immunosorbent assay (ELISA) for screening of donated blood in developing countries. Currently, however, specimens which test positive on a screening assay must still be confirmed by Western blot (immunoblot), a method which is not feasible in most developing-country laboratories. We examined whether a testing hierarchy which utilizes neither conventional ELISA nor Western blot can be reliably used for screening and confirmation of HIV infection in a high-risk population. In a retrospective analysis of 3,878 specimens which were screened for antibody to HIV in Kinshasa, Zaire, we observed that a testing hierarchy consisting of duplicate HIVCHEK screening assays followed by duplicate Serodia-HIV confirmatory assays resulted in correct confirmation of all ELISA- and Western blot-positive specimens. We conclude that such a testing hierarchy can produce highly accurate results for identification of positive specimens in routine HIV testing and provides a practical alternative to conventional methods of HIV screening and confirmation.

Blood Donors↗
PubMed1990

Prevention of perinatal HIV transmission: are there alternatives to pre-pregnancy serological screening in Kinshasa, Zaire?

Complete obstetrical and medical histories were obtained from 6312 women between the ages of 15 and 45 years who had undergone HIV serological tests. Individual factors were examined for sensitivity, specificity and positive predictive value of HIV infection. No individual risk factors for HIV infection were identified which had sensitivities greater than 60%. Combinations of factors were modelled by logistic regression. Only a model which included indicators of present illness with AIDS/HIV-related symptoms (i.e., chronic fever, diarrhea or profound weight loss) was predictive of HIV serostatus. These results suggest that identification of healthy women at high risk of HIV infection using non-serological information is not feasible. Thus, since the yearly cost of universal serological screening is prohibitively expensive in the Zairean context, HIV/AIDS education and prevention campaigns may in fact be a more cost-effective means of preventing perinatal transmission of HIV.

Adolescent↗
PubMed1989

Perinatal transmission of the human immunodeficiency virus type 1 to infants of seropositive women in Zaire.

To examine perinatal transmission of the human immunodeficiency virus type 1 (HIV-1) in Zaire, we screened 8108 women who gave birth at one of two Kinshasa hospitals that serve populations of markedly different socioeconomic status. For up to one year, we followed the 475 infants of the 466 seropositive women (5.8 percent of those screened) and the 616 infants of 606 seronegative women matched for age, parity, and hospital. On the basis of clinical criteria, 85 of the seropositive women (18 percent) had the acquired immunodeficiency syndrome (AIDS). The infants of seropositive mothers, as compared with those of seronegative mothers, were more frequently premature, had lower birth weights, and had a higher death rate in the first 28 days (6.2 vs. 1.2 percent; P less than 0.0001). The patterns were similar at the two hospitals. Twenty-one percent of the cultures for HIV-1 of 92 randomly selected cord-blood samples from infants of seropositive women were positive. T4-cell counts were performed in 37 seropositive women, and cord blood from their infants was cultured. The cultures were positive in the infants of 6 of the 18 women with antepartum T4 counts of 400 or fewer cells per cubic millimeter, as compared with none of the infants of the 19 women with more than 400 T4 cells per cubic millimeter (P = 0.02). One year later, 21 percent of the infants of the seropositive mothers had died as compared with 3.8 percent of the control infants (P less than 0.001), and 7.9 percent of their surviving infants had AIDS. We conclude that the mortality rates among children of seropositive mothers are high regardless of socioeconomic status, and that perinatal transmission of HIV-1 has a major adverse effect on infant survival in Kinshasa.

AIDS Serodiagnosis↗
PubMed1989

Field testing and comparative evaluation of rapid, visually read screening assays for antibody to human immunodeficiency virus.

Five rapid, visually read assays for detection of antibody against human immunodeficiency virus (HIV) were evaluated on fresh serum samples from 4000 prospective blood donors at Mama Yemo Hospital, Kinshasa, Zaïre. The sensitivity of the assays, based on 214 specimens positive by western blot, ranged from 84.6% to 99.1%. The specificity, based on 3664 samples negative by enzyme-linked immunosorbent assay (ELISA) or western blot, ranged from 92.7% to 98.8%. Three readers scored each test result independently; disagreement about test interpretation occurred in 1.2-8.3% of the specimens. There was no correlation between assay performance and assay principle (agglutination or dot immunobinding) or antigen source (viral lysate or recombinant). Assays such as these can be readily implemented in a developing country transfusion centre, where blood screening by ELISA is not practicable.

Agglutination Tests↗
PubMed1989

Vitamin A levels and mortality among hospitalized measles patients, Kinshasa, Zaire.

Treatment with high dose vitamin A has recently been recommended for children with measles in communities where vitamin A deficiency is a recognized problem. However, the relationship between vitamin A and measles mortality has not been clearly established. We studied serum vitamin A levels in 283 children less than or equal to 5 years of age admitted to Mama Yemo and Kalembe Lembe Hospitals in Kinshasa, Zaire, between January and March, 1987. Vitamin A levels were determined by high performance liquid chromatography. Vitamin A levels ranged from less than 5 to 63 micrograms/dl (median, 8). The overall case-fatality rate was 26 per cent. On univariate analysis, age less than 24 months, pneumonia on admission, lymphopenia (less than 2000/mm3), and lower vitamin A levels were associated with death during hospitalization. In a multivariate logistic regression model, a vitamin A level less than 5 micrograms/dl was associated with fatal outcome for children younger than 24 months old (relative risk = 2.9, 95 per cent CI 1.3, 6.8), but not for older children. Further studies are needed to determine whether low vitamin A levels predispose children to severe measles and the role of vitamin A supplements in the prevention of measles mortality.

Child, Preschool↗
PubMed1989

HIV infection in patients with tuberculosis in Kinshasa, Zaire.

To better define the interrelationship of infection with human immunodeficiency virus (HIV) and tuberculosis (TB), we conducted three HIV serosurveys of inpatients and outpatients with confirmed or suspected TB in Kinshasa, Zaire. HIV seroprevalence in hospitalized sanatorium patients did not change significantly in serosurveys conducted in 1985 and 1987 (92/231 [40%] versus 85/234 [36%]). These proportions were significantly higher than the 17% HIV seroprevalence observed in a 1987 serosurvey of 509 consecutive patients with an initial diagnosis of pulmonary TB seen at an outpatient TB diagnostic center in Kinshasa (p less than 0.001). HIV seroprevalence was higher in sanatorium patients with extrapulmonary TB (22/46 [48%]) and suspected pulmonary TB (60/132 [45%]) than in patients with bacteriologically confirmed pulmonary TB (94/287 [33%]) (p less than 0.02). Mycobacterium sputum isolation rates were similar in HIV-seropositive (28/34 [82%]) and HIV-seronegative patients (135/159 [85%]). All isolates were Mycobacterium tuberculosis. Eighteen (21%) of 84 HIV-seropositive sanatorium patients in 1987, who were followed for two months after admission, had died, compared with 11 (9%) of 128 HIV-seronegative patients (p less than 0.01). However, clearance rates of acid-fast bacilli from sputum after standard therapy were equally good in HIV-seropositive and HIV-seronegative survivors. With the growing AIDS problem, the serious TB burden in sub-Saharan Africa may become even more onerous and may critically overload the stressed African health care systems.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Human immunodeficiency virus infection among employees in an African hospital.

To define the prevalence and course of human immunodeficiency virus (HIV) infection, we examined prospectively a cohort of 2002 adult hospital workers in Kinshasa, Zaire. From 1984 to 1986 the prevalence of HIV infection increased from 6.4 percent to 8.7 percent. Over the two years there was a cumulative incidence of new HIV infection of 3.2 percent. The prevalence was higher among women (16.9 percent) and men (9.3 percent) under the age of 30 than among women (9.0 percent) and men (6.2 percent) over 30. Prevalence rates were similar among physicians (5.6 percent), laboratory workers (2.9 percent), and clerical workers (7.9 percent), but they were higher among female nurses (11.4 percent) and manual workers (11.8 percent). Despite marked differences in the intensity of nosocomial exposure, female nurses had similar infection rates on the female internal medicine ward (9.9 percent), in pediatrics (10.8 percent), and in the delivery room (10.7 percent). The attributable risk of HIV infection from a transfusion was 5.9 percent. Neither medical injections nor scarification was a risk factor for HIV infection. Of the 101 seropositive asymptomatic employees in the 1984 survey, 16 percent had AIDS-related complex, 3 percent had AIDS, and 12 percent had died of AIDS by 1986. Previous studies have revealed a seroprevalence of 8.4 percent among women attending an antenatal clinic near the hospital in 1984 and 1986, and of 5.8 percent (in 1984) and 6.5 percent (in 1986) among men donating blood at the hospital's blood bank. We conclude that there is a continuing high prevalence of HIV infection among hospital workers in Kinshasa, Zaire, which appears to be representative of that in the community and not nosocomial.

AIDS-Related Complex↗
PubMed1988

The prevalence of infection with human immunodeficiency virus over a 10-year period in rural Zaire.

In 1985 we tested 659 human serum samples, collected in the remote Equateur province of Zaire in 1976, for antibody to human immunodeficiency virus (HIV). Five (0.8 percent) were positive, and HIV was isolated from one of these. Follow-up investigations in 1985 revealed that three of the five seropositive persons had died of illnesses suggestive of acquired immunodeficiency syndrome (AIDS), and two remained healthy but seropositive. In 1986, a serosurvey we conducted using a cluster-sampling technique in the same region showed a seroprevalence of 0.8 percent in 389 randomly selected residents. The seroprevalence in 283 prostitutes was 11 percent. Patients with AIDS were identified in various hospitals in the province. Risk factors for AIDS included a greater than average number of sexual partners and residence outside the area. We believe that the long-term stability of HIV infection in residents of rural Zaire suggests that social change may have promoted the spread of AIDS in Africa.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Evaluation of the WHO clinical case definition for AIDS in rural Zaire.

The clinical case definition for AIDS proposed by WHO for use in Africa was evaluated against HIV antibody status in 72 patients in rural Zaire. Twenty-one (29%) of the patients were antibody-positive. For diagnosing anti-HIV seropositivity, the case definition had a sensitivity of 52%, a specificity of 78%, a positive predictive value of 50% and a negative predictive value of 80%. Calculation of the positive predictive value at different levels of prevalence of HIV infection suggests that the case definition operates at maximum reliability in selected high-risk groups. Modifications to the case definition should be evaluated to try and improve its sensitivity and positive predictive value.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Epidemiology of HIV infection in Africa.

HIV infection in Africa is primarily acquired through heterosexual activity, accounting for up to 80% of cases. Prostitutes and sexually promiscuous individuals are at particularly high risk of acquiring infection via this route. In the general population, women between the ages of 18 and 30 years are at increased risk of transmission. The role of cofactors, particularly concurrent sexually transmitted diseases (STDs), appears to facilitate heterosexual spread. These groups represent opportunities for targeted prevention programs aimed at education, increased condom use, prompt treatment of STDs, and reduction in the number of sexual partners. HIV infection acquired via blood transfusion may account for up to 10% of new cases of HIV infection. Children with malaria and nutritionally induced anemias are at special risk of acquiring infection by this route. Early treatment of malaria, surveillance for and treatment of malnutrition, adoption of rigorous criteria for blood transfusion, and implementation of machine-independent, low cost HIV screening programs in transfusion centers will help prevent these infections. As the epidemiology of HIV infection becomes better understood, other opportunities for technologically appropriate, cost-effective interventions will become available and will facilitate African HIV control and prevention programs.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Trials of intradermal hepatitis B vaccines in Gambian children.

Three trials of intradermal hepatitis B virus (HBV) vaccines were made in Gambian children. In the first trial HBV vaccine (1 microgram) was given to neonates in the same syringe with BCG followed by two further does of 1.0 microgram of intradermal HBV vaccine. The trial was a failure, for 19 of 32 subjects had an HBV surface antibody response of less than 10 m.i.u./ml. In the second trial in young children two different regimes were used: two doses of 2 micrograms HBV vaccine were given intradermally after a 20 micrograms intramuscular dose or three doses of 2 micrograms were given intradermally. In both cases geometric mean antibody responses were significantly lower than in the control group who were given 20 micrograms HBV intramuscularly followed by two 10 micrograms doses intramuscularly. Vaccine failures, defined as the presence of HBV surface antigen or core antibody or absence of surface antibody, were also significantly higher in the intradermal groups. In the third trial 4 micrograms of vaccine were given intradermally to 20 young children with a multiple orifice head fired by a jet gun: all had a good HBV surface antibody response of greater than 100 m.i.u./ml of serum.

Adjuvants, Immunologic↗
PubMed1986

An outbreak of nosocomial cholera in a rural Bangladesh hospital.

At a time of year when Vibrio cholerae infection accounted for over 50% of admissions to a rural Bangladeshi diarrhoea treatment centre, 29% of 48 patients hospitalized with non-cholera diarrhoea developed nosocomial V. cholerae infection. During an investigation of the 8-week outbreak, only the severity of the non-cholera diarrhoea which prompted hospital admission emerged as an important risk factor for nosocomial infection; food, intravenous solutions, oral rehydration fluid, patient attendants and hospital personnel could not be implicated as transmission sources. Patients receiving antibiotics while hospitalized did not develop nosocomial infection. Antecedent non-cholera diarrhoea may represent an important risk factor in some cases of V. cholerae infection occurring in persons who reside in cholera-endemic areas where rates of non-cholera diarrhoea are also high.

Adult↗
PubMed1986

Enzootic bovine rotavirus is not a source of infection in Panamanian cattle ranchers and their families.

Vaccination of humans against rotavirus (RV) diarrhea may be accomplished by oral immunization with attenuated animal strains known to be antigenically very similar to human strains. To define better the degree of infectivity in nature of these animal strains for humans, we conducted surveillance for RV infection/diarrhea in 180 farm workers, their 161 family contacts, and the 566 animals (512 cattle, 35 pigs, and 19 sheep) on 14 farms in rural Panama. No correlation between the high infection rates in farm workers (72%) and their family contacts (78%) and in cattle (56%) could be demonstrated. Heads of families with four or more children with RV infection experienced a twofold greater rate of RV infection compared with heads of families of similar size without RV infection. Despite the close similarity between human and bovine RV, in Panama intrafamilial (particularly child-to-child or child-to-parent) rather than interspecies transmission appeared to be the most important route for the spread of this highly infectious virus.

Age Factors↗