Search PubMed⌕ Search

Biomedical subjects

N T Constantine

Publications and source records attributed to N T Constantine.

At least 37 records · Page 2Linked to original sources
PubMed1994

Sensitivity of HIV-antibody assays determined by seroconversion panels.

OBJECTIVES: To determine the sensitivity of HIV-antibody assays for detecting low levels of HIV antibody using seroconversion and other panels containing plasma of varying titres. METHODS: Eight HIV-antibody assays, available under the World Health Organization bulk-procurement agreement, were evaluated on sets of sequential plasma samples derived from 11 individuals who had recently become HIV-infected (seroconversion panels). In addition, two non-seroconversion panels, consisting of low performance (titre) and mixed titre samples were used to further define the sensitivity of the assays. The eight assays included two rapid tests, one simple test, and five enzyme-linked immunosorbent assays (ELISA). RESULTS: On average, the eight assays detected antibody 0.5-4.8 days later than the reference test (Abbott HIV-1/HIV-2 3rd generation ELISA); these differences were statistically significant for six of the eight tests. All tests performed well on the low performance and mixed titre panels. All eight assays also had comparable sensitivity to that of the reference test on a large panel of known positive plasma. The additional risk of missing an infectious unit of blood during seroconversion by using the least sensitive rather than the reference test was estimated to be 1 in 7600 and 1 in 76 million at annual HIV incidence rates of 1 and 0.0001%, respectively. The cost of eliminating this additional risk by using the reference test is between US$ 15,150 and 151 million per unit detected at the above incidence rates. CONCLUSIONS: Although there are differences in sensitivity between the assays when used to test blood from individuals during the course of seroconversion, the differences are small, and all eight tests are appropriate for use as screening tests.

AIDS Serodiagnosis↗
PubMed1994

Serological diagnosis of HIV infection using oral fluid samples.

The serological identification of antibodies to human immunodeficiency virus (HIV) in blood is the most widely used method to diagnose HIV infection. Recently, however, the use of oral fluid samples for the detection of antibodies to HIV has been suggested as an alternative. This review describes some basic information about oral fluids, the application of these samples for HIV testing, and summarizes results from many of the studies performed using HIV tests with oral fluids. The fluids obtained from the oral cavity include saliva and crevicular fluid, and can be collected directly (by dribbling) or by using commercially available devices. The immunoglobulin content of oral fluids is similar to that of blood, but their levels are less. However, the use of an HIV IgG antibody capture assay (GAC ELISA) designed specifically for testing oral fluids, and certain routine HIV blood tests that have been optimized for use with oral fluids, has produced encouraging results. A number of studies, including several in developing countries, report that the sensitivities and specificities of these optimized tests lie in the range 95-100% and 98-100%, respectively. Also, the performance of the GAC ELISA was consistent and in general, excellent. The article identifies several issues that need to be addressed before a recommendation on the routine use of oral fluid samples for HIV antibody detection can be made.

AIDS Serodiagnosis↗
PubMed1993

Second generation hepatitis C virus assays: performance when testing African sera.

Sera were collected from 426 volunteers in Uganda at high and low risk for acquisition of hepatitis C virus (HCV). All samples were tested by the Ortho HCV second generation ELISA (S1) and by the INNOTEST HCV Ab second generation enzyme immunoassay, (S2), (Innogenetics, Antwerpen, Belgium). Sera that were repeatedly reactive by either screening assay were further tested by each of two different HCV supplemental/confirmatory assays: a second generation recombinant immunoblot assay (RIBA, Ortho Diagnostics), (C1), and a line immunoassay (INNO-LIA HCV-Ab, Innogenetics), (C2). In these populations there were 16 true positives, 351 true negatives, and 59 indeterminate results. Fifty-nine point four percent (253/426) of the samples were repeatedly reactive by the S1 test, while only 2.6% (11/426) were repeatedly reactive by S2. Test S1 produced a high false positive rate, a low positive predictive value, a specificity of 49.3%, and had a sensitivity of 100%. In contrast, the S2 screening assay had much higher specificity (98.8%), but lacked in sensitivity (31.3%). This poor sensitivity of S2 was based almost exclusively on the fact that the C2 supplemental test classified 9 samples as confirmed positive when the homologous screening assay classified these samples as negative; several of these were not confirmed when using a new generation INNO-LIA. Both the screening tests S1 and S2, and the supplemental assays C1 and C2 exhibited a significant degree of discordance, and neither of the screening tests alone would be adequate for use in these populations.

Adult↗
PubMed1993

Detection of antibodies to HIV in homologous sets of plasma, urine and oral mucosal transudate samples using rapid assays in Tanzania.

The aim of this study was to evaluate the performance of commercially available anti-HIV assays when testing plasma, urine and oral mucosal transudate (OMT) samples for the presence of antibodies to HIV. Homologous sets of plasma, urine and oral mucosal transudate specimens were collected from 288 hospitalized patients in northern Tanzania and tested for antibodies to HIV using a routine enzyme immunoassay (Recombinant 3rd Generation EIA, Abbott) and two rapid assays (Testpack HIV-1/HIV-2; Abbott and SUDS HIV-1, Murex). Incubation times and/or sample volumes when testing OMT or urine were increased as compared to those recommended for plasma. The corresponding plasma specimens from all repeatedly reactive samples and samples presenting discordant results were subjected to confirmational testing by an HIV-1/2 Western blot. A total of 15.3% (44/288) of the plasma samples were anti-HIV-1 positive by Western blot. The sensitivity using plasma was 100% by all assays, 69.7-97.7% using urine, and 92.7-100% using oral transudate specimens. The sensitivity of both rapid assays was excellent and higher than the EIA when testing OMT. Specificities ranged from 98.8-100% for plasma, 99-100% for urine and were 100% by all assays using oral samples. The results obtained using oral mucosal transudate specimens and rapid assays were at least comparable to those obtained with plasma, while the use of urine specimens produced suboptimal sensitivities with two of the three assays. The testing of alternative body fluids for antibodies to HIV is yet another strategy that may be applicable, particularly in developing countries.

Journal Article↗
PubMed1993

Evaluation of five hepatitis C virus screening tests and two supplemental assays: performance when testing sera from sexually transmitted diseases clinic attendees in the USA.

The performances of five screening tests (recombinant peptide-based first and second generation tests from Abbott and Ortho, and a synthetic peptide-based test from Biochem Immunosystems) and two supplemental tests: recombinant peptide- based, Abbott neutralization test and Chiron second generation recombinant immunoblot assay (RIBA 2), were evaluated for their ability to detect hepatitis C virus (HCV) antibodies in a population of 276 individuals attending a sexually transmitted diseases (STD) clinic in the USA. Although the five screening tests produced a variable number (35-62) of repeatedly reactive samples, only 13% (36/276) were classified as true positives by the supplemental tests. Thirty-four of the 36 were reactive by all screening tests and 32 of the true positives were reactive by both supplemental tests, while 2 did not neutralize but were reactive in the RIBA 2 test. Of the remaining 2 of the true positives which were discordant by several of the screening assays, 1 was confirmed by both supplemental assays but the other required a chemiluminescent enhancement technique to show positivity in RIBA 2. The sensitivities of the first and second generation Abbott and Ortho tests ranged from 97% to 100% and that of the Biochem test was 94%. The specificities of these tests ranged from 89.2% to 99.6%. The second generation Ortho test presented 9.4% (26/276) false positives. The use of second generation Ortho as a screening test would lead to an excessive number of confirmatory false positives. the positive predictive values of the screening tests ranged from 58.1% to 97.1%. Although the synthetic peptide based Biochem test exhibited the best overall indices, the presence of 2 false negative results would prevent its use as a singular screening test. Nevertheless its high specificity may lend itself to be used as a second screening test before confirmatory testing with RIBA 2.

Journal Article↗
PubMed1993

Risk factors associated with a high seroprevalence of hepatitis C virus infection in Egyptian blood donors.

We performed serologic tests for hepatitis C virus (HCV) infection on sera obtained from 163 volunteer blood donors seen at one Cairo hospital. We found HCV infection in 36 donors (22%) measured by a second generation enzyme immunoassay. Thirty-five of these 36 positive sera were tested with a second generation recombinant immunoblot assay (RIBA-2); 22 (63%) were reactive and another 12 (34%) showed an indeterminate reaction. Overall, 13.6% (95% confidence interval [CI] = 8.3-18.9%) of these Egyptian blood donors were serologically confirmed to be infected with HCV. Of several demographic variables and medical risk factors examined, the serologically confirmed (RIBA-2 reactive) donors were significantly older than nonreactive donors, and the age-adjusted risk of being HCV-positive was significantly greater in individuals residing outside Cairo. A knowledge of having received injections, of having a history of schistosomiasis, or of having concomitant hepatitis B surface antigen or antibody were significantly associated with an increased risk of HCV-seropositivity; however, after adjusting for confounding demographic factors, only schistosomiasis (odds ratio = 8.9, 95% CI = 2.35-33.52) was significantly associated with HCV infection. The HCV seropositive rate of 13.6% among Egyptians is 5-35-fold higher than that reported from volunteer blood donors in other countries. Screening for HCV should be instituted in Egyptian blood banks. Blood banks that do not test for HCV should include a history of schistosomiasis in their exclusion criteria used for routine screening of blood donors.

Adolescent↗
PubMed1993

Seroprevalence of parenterally transmitted viruses (HIV-1, HBV, HCV, and HTLV-I/II) in forensic autopsy cases.

HIV, HBV, HCV, and HTLV show similar modes of transmission and infection is frequently identified in certain population groups. The seroprevalence of these infectious agents and interrelation in forensic autopsy populations are described here. A total of 414 serum samples were collected sequentially from autopsy cases at the Office of the Chief Medical Examiner for the State of Maryland. All samples were tested for the presence of antibodies to HIV-1, HCV, HTLV-I/II, and hepatitis B core antigen, using Enzyme-linked Immunosorbent Assays (ELISA). Samples yielding repeatedly reactive results were confirmed by Western Blots (WB) for HIV-1 and HTLV-I/II, while for HCV confirmation, the second generation recombinant immunoblot (RIBA-2) was used. Of the 414 cases, 32.6% (135/414) were infected with at least one of the four viruses. 5.6% were seropositive for HIV-1, 23.2% for HBV, 19.1% for HCV, and 1.0% for HTLV-I/II. Intravenous drug users (IVDU) showed significant increased prevalences of HIV-1, HBV, and HCV. 83.6% of the IVDU were infected with at least one of the three viruses, 25.5% with HIV-1, and 47.3% with both HBV and HCV. The data indicate that the overall prevalence of HIV, HBV, and HCV seropositivity in the autopsy population of an inner city medical examiner office is much higher than that of the general population. Routine testing only for HIV-1 would have missed 86% of the infections with HCV or HBV. Universal precautions should be strictly employed by all personnel working in this environment.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Determination of human immunodeficiency virus antibody status in forensic autopsy cases using a rapid and simple FDA-licensed assay.

Evaluation of an FDA-licensed rapid assay to detect antibodies to human immunodeficiency virus (HIV) was accomplished by testing 414 serum samples collected sequentially from autopsy cases at the Office of the Chief Medical Examiner, State of Maryland. The time of postmortem collection ranged from 8 to 30 hours. All samples were tested for the presence of antibodies to HIV using a rapid peptide microfiltration assay (SUDS HIV-1 test, Murex Corporation, Norcross, GA), and an enzyme-linked immunosorbent assay (ELISA). Samples yielding repeatedly reactive results were confirmed by Western blot. Of the 414 specimens, 23 (5.6%) produced reactive results by both SUDS and ELISA, and were confirmed by Western blot. One additional sample was repeatedly reactive by ELISA but negative by the SUDS test. This sample produced an indeterminate profile by Western blot (reactivity to only p24) and was negative by several additional retroviral assays. Of the 23 HIV infected cases, 16 had risk factors for HIV infection; 19 were blacks and 18 were male. The SUDS, 10 minute test, exhibited a 100% sensitivity and 100% specificity in comparison to FDA-licensed ELISA and Western blot assays for detecting HIV antibody in autopsy serum specimens. We conclude that this rapid, simply performed assay is accurate and applicable for use in several testing situations, including autopsy rooms.

Adolescent↗
PubMed1993

Prevalence of HIV infection and AIDS in Egypt over four years of surveillance (1986-1990).

Serosurveys were conducted from April 1986 to March 1990 to determine the prevalence of HIV-1 infections among Egyptians and foreigners. Sera from 29,261 high risk individuals and blood or blood product donors in Egypt, and from 10,326 foreigners were tested for HIV-1 antibodies by a recombinant HIV-1 and a recombinant combination HIV-1/HIV-2 enzyme immunoassay (EIA). Any serum found to be repeatedly reactive by EIA was tested by Western blot for confirmation of HIV-1 infection. The overall prevalence of HIV-1 infection among the Egyptians was 0.18% (54/29,261); of which 4.8% (28/582) were blood and factor VIII recipients, 0.15% (3/1961) drug addicts, 0.18% (3/1650) fever of unknown origin patients, 0.23% (6/2602) sexually transmitted disease patients, 1.9% (5/269) HIV-1 contacts, 0.07% (7/9778) international travellers, and 0.02% (2/12,070) blood/product donors. Evidence of HIV-1 infection was not demonstrated among 349 prostitutes. The prevalence of HIV-1 antibody among foreigners was 0.97% (100/10,326), who were mainly (94%) from other African countries. Among the total 54 HIV infected Egyptians, 20 developed AIDS, and at least 12 have died. Only one of the 100 infected foreigners was diagnosed with AIDS. While the number of AIDS cases has increased in Egypt over 18 months October 1988-March 1990, the overall prevalence of new HIV infections has decreased since 1988 and endemic transmission has not been documented in Egypt.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Evaluation of a new generation synthetic peptide combination assay for detection of antibodies to HIV-1, HIV-2, HTLV-I, and HTLV-II simultaneously.

A new generation combination test (Detect-Plus, IAF BioChem, Montreal, Canada) based on synthetic peptides for HIV-1, HIV-2, HTLV-I, and HTLV-II was compared with three routine commercial screening assays and confirmatory assays to determine its sensitivity and specificity and to evaluate it as a substitute screening method. Samples from 356 sexually transmitted disease (STD) patients were tested by the four screening tests. All initially reactive samples were retested in duplicate by the corresponding EIA and repeatedly reactive samples were confirmed by Western blots for HIV-1, HIV-2, and HTLV-I/II. The confirmed positives detected by each screening assay were HIV-1 (23/356, 6.46%), HIV-2 (11/356, 3.09%), and HTLV-I/II (5/356, 1.4%). The new generation Detect-Plus test produced only two results (2/356, 0.56%) that were presumed to be false-positives in comparison to the screening tests, but the OD/CO values were just slightly high (1.5 and 1.9). There were no false-negative results, indicating that the sensitivity of the new combination test was excellent (100%). Compared with routine retroviral EIA assays, the test is easy to perform--the total time requirement is only 2 hr and there is no need for incubation equipment. The OD/CO values were very high when samples were positive, making even visual interpretation possible. We conclude that this new combination assay is an excellent screening method for detection of antibodies to the human retroviruses, and may be particularly useful for screening blood for transfusion and in epidemiological investigations.

Deltaretrovirus↗
PubMed1992

Efficacy of hepatitis B vaccination in primary school children from a village endemic for Schistosoma mansoni.

To determine whether chronic Schistosoma mansoni infection interferes with hepatitis B virus (HBV) immunization, 308 schoolchildren aged 6-12 years with no evidence of prior HBV infection (156 with active schistosomiasis) were vaccinated with three 5-micrograms injections of recombinant DNA-derived HBV vaccine. The vaccine was given in the deltoid muscle at time 0 and 1 and 7 months later. All vaccinees were examined 1 and 3 years after vaccination for quantitative antibody to hepatitis B surface antigen (anti-HBs). Seroconversion was detected in 284 vaccinated children (92%), of whom 271 had a good (51-300 mIU/mL) or excellent (greater than 300 mIU/mL) anti-HBs response. Sixteen other children (5%) had evidence of natural HBV infection (antibody to hepatitis B core antigen). Of those with good or excellent response, 99% retained high antibody titers for 3 years. Response was not influenced by S. mansoni infection. Hepatomegaly and splenomegaly were associated with reduced vaccine response.

Child↗