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PubMed2001

Seven human immunodeficiency virus (HIV) antigen-antibody combination assays: evaluation of HIV seroconversion sensitivity and subtype detection.

In this study, we evaluated the performance of two prototype human immunodeficiency virus (HIV) antigen-antibody (Ag-Ab) combination assays, one from Abbott Laboratories (AxSYM HIV Ag-Ab) and the other from bioMerieux (VIDAS HIV Duo Ultra), versus five combination assays commercially available in Europe. The assays were Enzygnost HIV Integral, Genscreen Plus HIV Ag-Ab, Murex HIV Ag-Ab Combination, VIDAS HIV Duo, and Vironostika HIV Uniform II Ag-Ab. All assays were evaluated for the ability to detect p24 antigen from HIV-1 groups M and O, antibody-positive plasma samples from HIV-1 groups M and O, HIV-2, and 19 HIV seroconversion panels. Results indicate that although all combination assays can detect antibodies to HIV-1, group M, subtypes A to G, circulating recombinant form (CRF) A/E, and HIV-1 group O, their sensitivity varied considerably when tested using diluted HIV-1 group O and HIV-2 antibody-positive samples. Among combination assays, the AxSYM, Murex, and VIDAS HIV Duo Ultra assays exhibited the best antigen sensitivity (at approximately 25 pg of HIV Ag/ml) for detection of HIV-1 group M, subtypes A to G and CRF A/E, and HIV-1 group O isolates. However, the VIDAS HIV Duo Ultra assay had a lower sensitivity for HIV-1 group M and subtype C, and was unable to detect subtype C antigen even at 125 pg of HIV Ag/ml. The HIV antigen sensitivity of the VIDAS HIV Duo and Genscreen Plus combination assays was approximately 125 pg of HIV Ag/ml for detection of all HIV-1 group M isolates except HIV-1 group O while the sensitivity of Vironostika HIV Uniform II Ag-Ab and Enzygnost HIV Integral Ag-Ab assays for all the group M subtypes was >125 pg of HIV Ag/ml. Among the combination assays, the AxSYM assay had the best performance for detection of early seroconversion samples, followed by the Murex and VIDAS HIV Duo Ultra assays.

AIDS Serodiagnosis↗

PubMed2004

Performance characteristics of the immunoglobulin G-capture BED-enzyme immunoassay, an assay to detect recent human immunodeficiency virus type 1 seroconversion.

Recently, we developed an immunoglobulin G (IgG)-capture BED-enzyme immunoassay (BED-CEIA) to identify recent human immunodeficiency virus (HIV) type 1 (HIV-1) seroconversion for use in incidence estimates. We have established an algorithm for its use; developed quality control reagents to monitor the assay; and evaluated its performance for interrun, intrarun, and operator variability. Analysis of 144 individual plates, which involved multiple plate lots and several operators over more than a year, indicated that the coefficients of variation (CVs) were between 10 and 15% for raw optical density (OD) values in the dynamic range between 0.5 and 2.0 OD units; the CVs decreased to 5 to 10% when the OD was normalized (OD-n; OD-n = specimen OD/calibrator OD). The intrarun CVs were generally in the range of 5 to 10% for specimens with ODs <0.5 and less than 5% for specimens with ODs >0.5. The level of concordance between multiple plate lots (n = 6) and multiple operators (n = 7) was quite high (R(2) > 0.9). Comparison of the results of the initial and the confirmatory tests with specimens with OD-n values </=1.5 demonstrated a high degree of correlation (R(2) = 0.92); 566 (92%) of 615 of specimens tested in the two modes retained the same classification (recent or long-term infection). The values for those specimens with changed classifications (n = 49) were close to the cutoff (OD-n = 1.0), as expected. The twofold difference in the HIV IgG contents between the controls and the calibrator reagents was exploited to monitor individual plate runs by using a control plot, which was incorporated into the spreadsheet for data entry and run monitoring. This information provides baseline data for the successful transfer of BED-CEIA to other laboratories and the use of BED-CEIA for the detection of recent HIV seroconversion and the calculation of incidence estimates worldwide.

HIV Antibodies↗

PubMed1995

Syncytium-inducing (SI) phenotype suppression at seroconversion after intramuscular inoculation of a non-syncytium-inducing/SI phenotypically mixed human immunodeficiency virus population.

Two distinct biological phenotypes of human immunodeficiency virus (HIV) have been described: the non-syncytium-inducing (NSI) phenotype, best characterized by the inability to infect MT-2 cells, and the syncytium-inducing (SI) phenotype, with the ability to infect MT-2 cells. The earliest virus population observed following HIV transmission is generally of the NSI phenotype, even after exposure to inocula of mixed NSI/SI phenotype. In this study, the issue of intrapatient selection of virus phenotype following transmission was addressed by studying two cases of accidental transmission. A comparison of the sequences of the V1-V2 and the V3 coding regions of the envelope gene and the p17 region of the gag gene showed that the donor-recipient pairs were tightly clustered in all gene segments, but away from local and published transmission controls. The intrasample variation of the p17 sequence was greater in the recipients and smaller in the donors than that of the V3 region sequence, indicating selection of V3 at transmission. In these transmission cases, the effects of an intravenous inoculation of a small quantity of blood containing predominantly SI V3 sequences (6 of 8 clonal sequences) were compared with those of an intramuscular inoculation of a large quantity of blood containing predominantly NSI viruses (14 of 16 clonal sequences). Both SI and NSI V3 regions were demonstrated to be phenotypic expressions of genetically related viral strains. The inoculation of the predominantly SI virus population resulted in the persistence of an SI virus population in the recipient and a rapid CD4+ T-cell decline. The inoculation of the predominantly NSI population resulted in a selective amplification of SI viruses before seroconversion, followed by a suppression of SI viruses at seroconversion and a rapid decline of CD4+ T-cell numbers. These data suggest that the suppression of SI viruses can be accomplished following the development of HIV-specific immunity and that the ability to suppress SI viruses does not prevent the development of immunodeficiency.

Acquired Immunodeficiency Syndrome↗

PubMed2001

Human immunodeficiency virus seroconversion and evolution of the hepatitis C virus quasispecies.

When chronic hepatitis C virus (HCV) infections are complicated by acquisition of human immunodeficiency virus (HIV), liver disease appears to accelerate and serum levels of HCV RNA may rise. We hypothesized that HIV might affect the HCV quasispecies by decreasing both complexity (if HIV-induced immunosuppression lessens pressure for selecting HCV substitutions) and the ratio of nonsynonymous (d(N)) to synonymous (d(S)) substitutions, because d(N) may be lower (if there is less selective pressure). To test this hypothesis, we studied the evolution of HCV sequences in 10 persons with chronic HCV infection who seroconverted to HIV and, over the next 3 years, had slow or rapid progression of HIV-associated disease. From each subject, four serum specimens were selected with reference to HIV seroconversion: (i) more than 2 years prior, (ii) less than 2 years prior, (iii) less than 2 years after, and (iv) more than 2 years after. The HCV quasispecies in these specimens was characterized by generating clones containing 1 kb of cDNA that spanned the E1 gene and the E2 hypervariable region 1 (HVR1), followed by analysis of clonal frequencies (via electrophoretic migration) and nucleotide sequences. We examined 1,320 cDNA clones (33 per time point) and 287 sequences (median of 7 per time point). We observed a trend toward lower d(N)/d(S) after HIV seroconversion in 7 of 10 subjects and lower d(N)/d(S) in those with rapid HIV disease progression. However, the magnitude of these differences was small. These results are consistent with the hypothesis that HIV infection alters the HCV quasispecies, but the number of subjects and observation time may be too low to characterize the full effect.

Adult↗

PubMed2002

Distribution of chemokine receptor CCR2 and CCR5 genotypes and their relative contribution to human immunodeficiency virus type 1 (HIV-1) seroconversion, early HIV-1 RNA concentration in plasma, and later disease progression.

At the CC (beta) chemokine receptor 2 (CCR2) and CCR5 loci, combinations of common single-nucleotide polymorphisms (SNPs) and a 32-bp deletion (Delta32) form nine stable haplotypes (designated A through G*2). The distribution of these CCR2-CCR5 haplotypes was examined among 703 participants in the Multicenter AIDS Cohort Study (MACS), the District of Columbia Gay (DCG) Study, and the San Francisco Men's Health Study (SFMHS). Highly exposed and persistently seronegative (HEPS; n = 90) Caucasian men from MACS more frequently carried heterozygous G*2 (Delta32) genotypes (especially A/G*2) and less frequently carried the homozygous E/E genotype compared with 469 Caucasian seroconverters (SCs) from the same cohort (P = 0.004 to 0.042). Among 341 MACS Caucasian SCs with 6- to 12-month human immunodeficiency virus type 1 (HIV-1) seroconversion intervals and no potent antiretroviral therapy, mean plasma HIV-1 RNA level during the initial 42 months after seroconversion was higher in carriers of the E/E genotype and lower in those with the 64I-bearing haplotype F*2 or the Delta32-bearing haplotype G*2 (and especially genotypes A/G*2 and F*2/G*2). A multivariable model containing these CCR markers showed significant composite effects on HIV-1 RNA at each of four postconversion intervals (P = 0.0004 to 0.050). In other models using time to AIDS as the endpoint, the same markers showed more modest contributions (P = 0.08 to 0.24) to differential outcome during 11.5 years of follow-up. Broadly consistent findings in the larger MACS Caucasian SCs and the smaller groups of MACS African-American SCs and the DCG and SFMHS Caucasian SCs indicate that specific CCR2-CCR5 haplotypes or genotypes mediate initial acquisition of HIV-1 infection, early host-virus equilibration, and subsequent pathogenesis.

Acquired Immunodeficiency Syndrome↗

PubMed1992

Effect of serotesting with counselling on condom use and seroconversion among HIV discordant couples in Africa.

OBJECTIVE: To determine whether HIV testing and counselling increased condom use and decreased heterosexual transmission of HIV in discordant couples. DESIGN: Prospective study. SETTING: Kigali, the capital of Rwanda. SUBJECTS: Cohabiting couples with discordant HIV serology results. MAIN OUTCOME MEASURES: Condom use in the couple and HIV seroconversion in the negative partners. RESULTS: 60 HIV discordant couples were identified, of whom 53 were followed for an average of 2.2 years. The proportion of discordant couples using condoms increased from 4% to 57% after one year of follow up. During follow up two of the 23 HIV negative men and six of the 30 HIV negative women seroconverted (seroconversion rates of 4 and 9 per 100 person years). The rate among women was less than half that estimated for similar women in discordant couples whose partners had not been serotested. Condom use was less common among those who seroconverted (100% v 5%, p = 0.01 in men; 67% v 25%, p = 0.14 in women). CONCLUSIONS: Roughly one in seven cohabiting couples in Kigali have discordant HIV serological results. Confidential HIV serotesting with counselling caused a large increase in condom use and was associated with a lower rate of new HIV infections. HIV testing is a promising intervention for preventing the spread of HIV in African cities.

AIDS Serodiagnosis↗

PubMed1996

Hepatitis C virus seroconversion by a third generation ELISA screening test in blood donors.

The significance of seroconversion as detected by an ELISA screening test for hepatitis C virus (HCV) antibody with a negative supplemental/confirmatory recombinant immunoblot assay (RIBA) result was investigated. Of 118,220 established West Midlands blood donors with at least one negative HCV antibody screen, 43 had seroconverted in 1994 according to the ELISA but had negative RIBA-3 results. The paired archive serum samples of the pre- and postseroconversion donations of 29 seroconverting donors were tested by nested polymerase chain reaction (PCR) for the detection of HCV RNA. All 58 samples were negative by PCR. The absence of detectable viraemia in all tested seroconverting donors suggests that HCV infection was not responsible for seroconversion by ELISA.

Blood Donors↗

PubMed2000

Seroconversion and seroreversion in IgG antibodies to Helicobacter pylori: a serology based prospective cohort study.

STUDY OBJECTIVES: To assess the incidence of seroconversion and seroreversion in IgG antibodies to Helicobacter pylori within a 11 year observation period using these events as markers for acquisition and loss of the infection, respectively. DESIGN: Population based prospective cohort study. SETTING: Northern part of Copenhagen County, Denmark. PARTICIPANTS AND METHODS: A random sample of 2527 Danish adults were examined and blood obtained in 1983 and in 1994. Matching pairs of sera were analysed for the presence of IgG and IgM antibodies to H pylori with an in house enzyme linked immunosorbent assay. Participants who were seronegative at study entry and seropositive at follow up and had a fourfold increase in baseline IgG antibody levels were categorised as seroconverters and regarded as having acquired H pylori infection. Participants who were seropositive at study entry and had at least a fourfold decrease in baseline IgG antibody levels at follow up were assumed to have lost the infection (seroreverters). RESULTS: The seroprevalence of H pylori infection was 24.7 (95% confidence intervals (95% CI) 23.0, 26.4) % in 1983 and 24.5 (95% CI 22.8, 26. 2) % in 1994. A total of 14 participants seroconverted within the observation period (cumulative 11 year incidence proportion: 1.0 (95% CI 0.5, 1.5) %). Having increased IgM antibody levels at study entry significantly increased the likelihood of IgG seroconversion (relative risk 6.4 (95% CI 2.1, 19.6). Seroreversion was seen in 48 participants (cumulative 11 year incidence proportion: 7.7 (95% CI 5. 6, 9.8) %). CONCLUSIONS: Changes in H pylori infection status with time are rare in Danish adults. Few adults become infected with H pylori in Denmark.

Adult↗

PubMed1997

Seroconversion in an industrial unit of rabbits infected with a non-pathogenic rabbit haemorrhagic disease-like virus.

A serological survey of 238 rabbits for antirabbit haemorrhagic disease virus (RHDV) antibodies was made in an industrial rabbitry where no signs of the disease had been reported for four years. Seroconversion was repeatedly detected and was due to a calicivirus antigenically related to RHDV but without its pathogenicity. There was a seroprevalence of 33.3 per cent among young animals at weaning at 31 days old, 27.6 per cent at five to seven days after weaning, 56.1 per cent at 13 to 14 days after weaning, 90.3 per cent at 19 to 20 days and 100 per cent at 32 to 33 days after weaning, and all the breeding rabbits were seropositive. In the last group and in the young at weaning, the anti-RHDV antibodies were mainly class IgG, but they were IgM and IgA at 13 to 14 days after weaning. In older fattening rabbits, there was a decrease of IgM and IgA and an increase of IgG confirmed seroconversion without any specific signs of rabbit haemorrhagic disease. On the basis of these results, the probable time of infection of the meat rabbits with this non-pathogenic virus was immediately after weaning.

Animal Husbandry↗

PubMed1997

Determinants of HIV seroconversion in injection drug users during a period of rising prevalence in Vancouver.

To identify determinants of HIV seroconversion among injection drug users (IDUs) during a period of rising prevalence, a case-control investigation was conducted. Cases were IDUs with a new positive test after 1 January 1994, and a negative test within the prior 18 months. Controls required 2 negative tests during the same period. Subjects completed a questionnaire on demographic, psychosocial, and behavioural factors. Eighty-nine cases and 192 controls were similar with respect to gender, age, ethnicity and inter-test interval. Multivariate analyses of events during the inter-test interval showed borrowing syringes (adj. OR = 2.96; P < 0.006), unstable housing (adj. OR = 2.01; P = 0.03) and injecting > or = 4 times daily (adj. OR = 1.71; P = 0.06) to be independently associated with seroconversion. Protective associations were demonstrated for sex with opposite gender (adj. OR = 0.36; P = 0.001) and tetrahydrocannabinol use (adj. OR = 0.41; P = 0.001). There is a need to evaluate programmes dealing with addiction, housing and the social underpinnings of risk behaviours in this population.

Adult↗

PubMed1995

Rates of seroconversion in the progeny of Brucella abortus seropositive and seronegative cattle and buffalo.

The authors estimated the rates of development of serum antibodies against Brucella abortus, between January 1987 and December 1990, in female Jersey cattle and buffalo weaned from seropositive and seronegative dams, and used logistic regression analysis to examine the epidemiological relationship of these rates with the serum antibody status of dams. The offspring from both seropositive and seronegative dams were reared together in calf pens, while separate pens were used for bovine and buffalo calves. Each of the bovine calves was manually fed two litres of bulked milk (pooled from seronegative and seropositive cows) twice a day, in the morning and evening. The buffalo calves, however, were allowed to suckle their respective dams before and after manual milking of each buffalo, in the morning and evening. Bovine calves and buffalo calves were weaned at approximately six months of age and moved to sheds for young livestock. At maturity, the female offspring were artificially inseminated, and pregnancy was subsequently diagnosed by rectal palpation. The rate of seroconversion in the progeny of seropositive Jersey cattle was 26.4% (14 of 53 animals) compared to 14.3% (11 of 77 animals) in the progeny of seronegative cattle; this difference was non-significant (P = 0.1342). In buffalo, however, the rate of seroconversion in the progeny of seropositive dams (43.3% = 13/30) was significantly higher (P = 0.0002) than in the progeny of seronegative buffalo (8.8% = 6/68). The logistic regression analysis revealed that the progeny of seropositive buffalo were approximately 6.2 times more likely to have developed serum antibodies by the time of first calving than the progeny of seronegative buffalo (adjusted odds ratio [OR]) = 6.2; 95% confidence interval [CI] = 1.5, 36.4). This relationship was non-significant, however, for the progeny of seropositive cattle (adjusted OR = 2.1; 95% CI = 0.6, 7.4). The implications of these results and potential sources of bias are discussed.

Animals↗

PubMed1990

Seroconversion to human immunodeficiency virus in prison inmates.

We evaluated the prevalence and incidence of human immunodeficiency virus (HIV) infection in 3,837 inmates of a state prison system. Ninety-two (2.4 percent) were HIV-seropositive. The highest proportion of HIV-seropositive inmates was found among Blacks (5.4 percent), females, and those 30 years of age or older. HIV-seropositivity of entering inmates was also 2.4 percent and was unchanged over the three years of the study. Seroconversion occurred in two inmates while in prison, a rate of one conversion per 604 person-years, but HIV infection could have occurred before entry. Seroconversion to HIV was rare in inmates in this correctional facility.

Adult↗

PubMed1991

Incidence of hepatitis and seroconversion to hepatitis C virus after open-heart surgery in transfused and non-transfused patients in Sweden.

The transmission of non-A, non-B hepatitis (NANB)/hepatitis C virus (HCV) was studied in patients undergoing open-heart surgery and related to the reception of blood products and hospitalization and surgery per se. Posttransfusion hepatitis NANB was noticed in 17/390 (4.4%) patients receiving heterologous blood and 8/16 tested became positive for anti-HCV (Ortho HCV ELISA), all within 5 months after onset of hepatitis. Among patients with normal ALAT before surgery and during follow-up, who had received heterologous blood, 1/50 seroconverted after 6 months. This patient probably had a subclinical HCV infection, or possibly a temporary non-specific anti-HCV reactivity with a maximum optical density/cut-off ratio (OD/CO) of 1.2, whereas all posttransfusion hepatitis C cases had OD/CO ratios greater than 4. No hepatitis occurred among the 92 non-transfused patients and no seroconversion was found in any of 62 non-transfused patients tested 6 months after the operation. It was concluded that (1) hospitalization and surgery per se does not seem to offer a risk of hepatitis NANB/C, and (2) seroconversion to for HCV occurs in only 50% of Swedish patients with acute posttransfusion NANB hepatitis.

Alanine Transaminase↗

PubMed1996

Incidence rate and risk factors for HCV seroconversion among injecting drug users in an area with low HIV seroprevalence.

We conducted a study on injecting drug users attending one of 3 drug treatment centres in Naples, to estimate HIV and hepatitis C virus (HCV) incidence rates and to identify risk factors for seroconversion. Incidence rates were estimated using as denominator the person-time of follow-up of participants who were negative for both HIV and HCV at enrollment and who were retested within 6-12 months. Information on risk factors was collected using a standardized questionnaire. A nested case-control analysis was performed comparing seroconverters with persistently HCV-negative individuals. None of the initially non-infected participants seroconverted for HIV, while the incidence rate for HCV infection was approximately 29 per 100 person-years. Analysis of risk factors showed that age > 28 years and injecting use of cocaine were associated with HCV seroconversion. The protective role of methadone treatment was also marginally significant. Our findings suggest that HCV infection may represent an important public health problem in areas with low HIV circulation. The identification of specific risk factors for HCV infection is needed to plan effective prevention strategies.

Case-Control Studies↗

PubMed1994

Universal emergence of precore mutant hepatitis B virus along with seroconversion to anti-HBe irrespective of subsequent activity of chronic hepatitis B.

OBJECTIVES: It has been controversial whether or not the emergence of precore mutant HBV is related to the severe form of chronic hepatitis B (CH-B). To further clarify the role of the precore mutant HBV in the natural course of CH-B, we conducted a longitudinal analysis of precore-region sequences according to the biochemical severity along with seroconversion to anti-HBe in patients with CH-B. METHODS: The precore sequences of the ten sets of serial serum samples, obtained from 6 chronic hepatitis B patients with (group I) and from 4 patients without subsequent biochemical remission after seroconversion to anti-HBe (group II), were analyzed by direct sequencing of DNA amplified by PCR. RESULTS: The precore mutant HBV having a G-A mutation at the nucleotide 1896 was most commonly found (9/10). Wild-type precore HBV was detected in 4 of 6 (66.7%) in group I and 3 of 4 (75.0%) in group II during HBeAg-positive period (p > 0.05), and during anti-HBe-positive period it was found in 2 of 6 (33.3%) in group I and 0 of 4 (0%) in group II (p > 0.05). In contrast, precore mutant HBV was detected in 5 of 6 (83.3%) in group I and 2 of 4 (50.0%) in group II during HBeAg-positive period (p > 0.05), and in all patients of both groups during anti-HBe-positive period. CONCLUSION: The most common type of precore mutant HBV in Korea was the mutant with a G-A mutation at nucleotide 1896. The emergence of precore mutant HBV was a universal phenomenon during the natural history of CH-B; therefore, the precore mutant does not appear to have an pathogenic role in determining the severity of the CH-B.

Adult↗

PubMed2000

Seroconversion rate following measles vaccination.

OBJECTIVE: To assess the seroconversion rate following measles vaccination in Sri Lankan children. DESIGN: A descriptive study. SETTING: Immunisation clinic, Lady Ridgeway Hospital, Colombo (LRHC). SUBJECTS: 134 infants who attended the LRHC for measles vaccination. MEASUREMENTS: Pre- and post-vaccination blood samples were collected and serum was tested for the presence of anti-measles 1gG antibodies using the ELISA technique. RESULTS: Of the 134 infants only 102 were brought for the post-vaccination sample. Of these 102 samples, 101 were negative for anti-measles antibodies before vaccination. Of the 101 sero-negative samples 94 became sero-positive 6 to 8 weeks after vaccination. These results indicate that the seroconversion rate is 93.06%, which is similar to the results of studies done in other countries. CONCLUSION: Most infants are susceptible to measles infection by the age of 9 months, and it is appropriate to vaccinate infants at this age, as is the practice at present. However, further studies are needed to assess the duration of protection with a single dose of measles vaccine.

Antibodies, Viral↗

PubMed1989

Seroconversion after administration of measles vaccine to central Australian Aboriginal children at nine months of age.

A simple procedure for examining the seroconversion rates to measles vaccines in outlying communities is described; this involves the storage and transportation of dried-blood samples on filter paper, which is followed by the detection of measles-specific antibodies by means of a commercially-available immunofluorescence assay. Among 82 susceptible central Australian Aboriginal infants who were vaccinated at nine months of age, 76 (93% [95% confidence limits, 84.9%-96.6%]) children demonstrated seroconversion as a result of the vaccine, which is a figure that is similar to those that have been reported from some developing countries. The implications for a measles-vaccination policy are discussed.

Age Factors↗

PubMed1989

Incidence and risk factors for human immunodeficiency virus seroconversion in a cohort of Sydney homosexual men.

By means of prospective cohort data from the Sydney AIDS Project, we report on 55 homosexual or bisexual men who have become infected with human immunodeficiency virus (HIV), as measured by the development of serum HIV antibodies (seroconversion). We have compared the sexual practices, recreational drug abuse, history of sexually-transmissible diseases, and antecedent immunological findings of the men who seroconverted with those of 588 subjects who persistently remained seronegative in the same time-period. The cumulative incidence rate of HIV infection over the three years of observation was 8.5%. The cumulative incidence rate ranged from less than 1% for the six months before August 1, 1984, to a peak of 5% in the six months before August 1, 1985. Of those subjects for whom we had data for the period of seroconversion, all but two of the subjects who seroconverted admitted to a recognized high-risk sexual practice in the six months before the first visit at which they were found to be seropositive. Univariate analysis found that men who seroconverted were significantly more likely to have had a greater number of recent sexual partners (relative risk per partner, 1.02; P less than 0.001), to have engaged in receptive anal intercourse (incidence rate ratio, 3.1; 95% confidence interval [CI], 1.3-7.6; P = 0.01) and to have used nitrite inhalant (incidence rate ratio, 2.6; 95% CI, 1.2-5.9; P = 0.02) and amphetamine (incidence rate ratio, 4.8; 95% CI, 2.2-10.5; P less than 0.001) drugs. The men who seroconverted were significantly (incidence rate ratio, 2.7; 95% CI, 1.2-6.1; P = 0.014) more likely to have antecedent T-suppressor-cell counts of greater than 800 cells/microL. Factors that retained significance in multivariate analysis were the number of recent sexual partners, recent amphetamine abuse and a T-suppressor-cell count of greater than 800 cells/microL.

Adolescent↗