Incidence of symptoms and AIDS in 146 Swedish haemophiliacs and blood transfusion recipients infected with human immunodeficiency virus

Estimation in emerging epidemics: biases and remedies

When analysing new emerging infectious disease outbreaks, one typically has observational data over a limited period of time and several parameters to estimate, such as growth rate, the basic reproduction number R₀, the case fatality rate and distributions of serial intervals, generation times, latency and incubation times and times between onset of symptoms, notification, death and recovery/discharge. These parameters form the basis for predicting a future outbreak, planning preventive measures and monitoring the progress of the disease outbreak. We study inference problems during the emerging phase of an outbreak, and point out potential sources of bias, with emphasis on: contact tracing backwards in time, replacing generation times by serial intervals, multiple potential infectors and censoring effects amplified by exponential growth. These biases directly affect the estimation of, for example, the generation time distribution and the case fatality rate, but can then propagate to other estimates such as R₀ and growth rate. We propose methods to remove or at least reduce bias using statistical modelling. We illustrate the theory by numerical examples and simulations.

Transfusion-Associated HIV Infection in Mexico Related to Paid Blood Donors; HIV Epidemic

The objective of the study was to describe the clinical, epidemiological profile and conditional incubation period in a group of transfusion-associated HIV-infected (TAHI) patients seen in five national tertiary care centres in Mexico from 1983 to April 1998. Date of transfusions, AIDS diagnoses, opportunistic infections and malignancies were collected. The incubation period was estimated through a non-parametric conditional analysis.

One hundred and fifty-seven TAHI cases were analysed. The frequency of TAHI by year of transfusion was: 0.6% in 1980 and 1981, 4.5% in 1984, 22.4% in 1985, 54.5% in 1986, 10.3% in 1987, 0.6% in 1988, 1.9% in 1989 and 1990, 1.3% in 1993 and 0.6% in 1994 and 1996. The median incubation period was 4.3 years.

A well-defined epidemic period of HIV-infection among blood-recipients was identified that coincided with the HIV-epidemic among paid donors. TAHI patients in Mexico developed AIDS in a shorter time than that described for other populations.

Long-term follow up of HIV-1-infected Korean haemophiliacs, after infection from a common source of virus

In the early 1990s, 20 haemophiliacs (HPs) were infected with a common source of HIV-1 viruses through the contaminated clotting factor IX. The aim of this study is to review 20 HPs infected with a common source of virus. The enrolled patients have been consecutively treated with Korean red ginseng (KRG), zidovudine (ZDV) or two-drug therapy and highly active antiretroviral therapy (HAART). We determined full-length pol gene over 20 years and human leukocyte antigen (HLA) class I with peripheral blood mononuclear cells and reviewed medical records. Eighteen HPs experienced various opportunistic infections or clinical manifestations. There were significant inverse correlations between the HLA prognostic score and the annual decrease in CD4+ T-cell counts prior to HAART (AD) (P < 0.05) and the amount of KRG and the AD (P < 0.01). From 1998, the HPs had been treated with HAART. Each of the two patients died without and with HAART regimen respectively. At present, 16 HPs have been alive with HAART. Among the 16 HPs, 12 and 4 are on HAART-plus-KRG and HAART only respectively. Eleven HPs including 2 HPs with G-to-A hypermutations had revealed resistance mutations. Ten and two HPs have shown poor adherence and incomplete viral suppres-sion on HAART respectively. Virological failure based on WHO guidelines was not observed on KRG-plus-HAART. Two HPs revealed additional resistance mutations against two classes on KRG-plus-HAART. As a nationwide study, we first report overall features on clinical course of Korean haemophiliacs. Further education on the importance of drug adherence is needed.

STATISTICAL CHALLENGES OF AIDS: (The 1990 Knibbs Lecture, Canberra, 27 November 1990)

"This paper considers questions concerning the incubation period [of HIV infections], the effects of treatments, prediction of AIDS cases, the choice of surrogate end points for the assessment of treatments and design of strategies for screening blood samples. These issues give rise to a broad range of intriguing problems for statisticians. We describe some of these problems, how they have been tackled so far and what remains to be done. The discussion touches on topical statistical methods such as smoothing, bootstrapping, interval censoring and the ill-posed inverse problem, as well as asking fundamental questions for frequentist statistics." The geographical scope is worldwide, with some data for selected developed countries used to illustrate the models.

Uncertainty of AIDS incubation time and its effects on back-calculation estimates

Incubation time is the period from the onset of HIV infection to AIDS. The distribution of the incubation time is one of the main parameters of the back-calculation method for the estimation of incidence of HIV infection. Because of the long and variable incubation time, the assessment of its distribution is uncertain and this uncertainty spreads through the back-calculation method and affects the estimation of the precision of incidence of HIV infection. We propose a method to investigate the sensitivity of the estimates to variations of the incubation times, with particular regard to the covariate AGE in the modelling of the incubation period, making use of the parametric bootstrap. An application to the HIV epidemic in Italy is presented. The amplification of the uncertainty of the HIV incidence estimates resulting from the implementation of our proposed method tends to concentrate around the earlier periods of the epidemic, corresponding to the right tail of the incubation time distribution, which is very sensitive to small perturbations.

Comparison of clinical manifestations of HIV infection among women by risk group, CD4+ cell count, and HIV-1 plasma viral load. HER Study Group. HIV Epidemiology Research

OBJECTIVES

To compare the prevalence of HIV-related symptoms, physical examination findings, and hematologic variables among women whose risk for HIV is injection drug use since 1985 as opposed to sexual contact and to evaluate the influence of HIV plasma viral load and CD4+ cell count on clinical manifestations according to risk.

METHODS

Participants of the HIV Epidemiology Research Study (HERS; a multicenter, prospective, controlled study of HIV infection in women) were administered a risk behavior and symptom interview, underwent a physical examination, and received hematologic testing, including CD4+ cell counts done on study entry. Plasma HIV-1 viral loads were performed on stored frozen plasma using an ultrasensitive branched-DNA (b-DNA) signal amplification assay. CD4+ counts were categorized as <200 cells/microl, 200 to 499 cells/microl, or > or =500 cells/microl, and HIV viral loads were characterized in tertiles.

RESULTS

Cross-sectional analysis was conducted on data available for 724 HIV-infected women: 387 had a history of intravenous drug use and 337 were infected through heterosexual contact. The median CD4+ count was 376 cells/microl; the median HIV-1 viral load was 1135 copies/ml; and 281 of 724 HIV-infected women (38.8%) had an undetectable HIV-1 viral load. In analyses adjusting for CD4+ cell level alone and for plasma viral load combined with CD4+ cell level, injection drug users (IDUs) were more likely than those infected through heterosexual contact to report a recent episode of memory loss and weight loss, but less likely to have recent episodes of genital herpes; to have enlarged livers and a body mass index (BMI) <24, and to have hematocrit levels <34% and platelet counts <150,000 cells/ml. After adjustment for CD4+ cell level and risk group, high and medium HIV-1 plasma viral load levels were associated with the presence of oral hairy leukoplakia on examination, and only the highest level of plasma viral load was associated with recent histories of fever and thrush, oral hairy leukoplakia, pseudomembranous candidiasis, and BMI <24 on examination, and hematocrit <34%.

CONCLUSIONS

In this cohort of women, the distribution of HIV-1 plasma viral load was lower than that previously reported in populations of HIV-infected men. This study also shows some differences in frequency of signs, symptoms, and laboratory values between risk groups of HIV-infected women, but these results may be due to effects of injection drug use rather than HIV infection. Signs and symptoms identified as associated with increasing levels of viral load that were not different across risk groups suggest more direct association of these findings with HIV infection.

Longer survival after HIV infection for injecting drug users than for homosexual men: implications for immunology

BACKGROUND

Comparisons of progression in HIV-1 infection between injecting drug users (IDU) and homosexual men have been inconclusive due to the short follow-up periods, often with less well-defined starting points and endpoints. In addition, comparisons of survival after injection have been to some extent obscured by higher non-AIDS mortality in IDU.

METHOD

In a retrospective cohort study, homo-/bisexual men and IDU were followed, with dates of seroconversion defined within +/- 1 year by a previously negative HIV antibody test. Endpoints were CD4 cell count below 200 x 10(6)/l, AIDS and death from AIDS.

RESULTS

Sixty-three homo-/bisexual men and 125 IDU fulfilled the entry criteria, with no significant differences in age at or date for seroconversion. Mean follow-up times were 6.7 and 7.0 years, respectively. The homo-/bisexual group had a significantly accelerated progression rate to all three endpoints: time to CD4 cell count below 200 x 10(6)/l (P = 0.002), to AIDS (P = 0.0003), and to death from AIDS (P < 0.0001). Adjusting for age and sex only made marginal alterations. Ten years after infection, 54% of homosexual men had developed an AIDS-defining condition and 51% had died from AIDS, whereas the corresponding precentages in the IDU group were 26 and 15, respectively. There was, however, no difference in overall mortality due to almost constant, non HIV-related, yearly mortality of some 4% in IDU.

CONCLUSIONS

In our cohort there was a highly significant difference in disease progression and death from AIDS between homo-/bisexual men and IDU. This difference was proposed to be due to the transmission route determining the initial immune response and suggested that this route may have played a more important role than virus variability of the subsequent prognosis.

Category of exposure to HIV and age in the progression to AIDS: longitudinal study of 1199 people with known dates of seroconversion. HIV Italian Seroconversion Study Group

OBJECTIVES

To determine whether rate of development of AIDS is affected by category of exposure to HIV and whether the more rapid development found in older subjects persists for each exposure category.

DESIGN

Longitudinal study of people with known date of seroconversion to HIV.

SETTING

16 HIV treatment centres throughout Italy.

SUBJECTS

1199 people infected with HIV through use of injected drugs, homosexual sex, or heterosexual sex.

MAIN OUTCOME MEASURES

AIDS as defined by 1987 definition of Centers for Disease Control (including and excluding neoplasms) and by 1993 European definition.

RESULTS

225 subjects (18.8%) progressed to AIDS (Centers for Disease Control 1987 definition) during median follow up of 5.8 years. Univariate analyses showed more rapid progression to AIDS for older subjects compared with younger subjects and for homosexual men compared with other exposure categories. The age effect was of similar size in each exposure category and in men and women. In a bivariate model with age and exposure categories simultaneously included as covariates, differences by exposure category disappeared for use of injected drugs and heterosexual sex compared with homosexual sex (relative hazards 1.02 (95% confidence interval 0.71 to 1.45) and 1.07 (0.70 to 1.64) respectively), while the age effect remained (relative hazard 1.55 (1.32 to 1.83) for 10 year increase in age). Analyses using the other definitions for AIDS did not appreciably change these results.

CONCLUSIONS

There was no evidence of differences in rate of development of AIDS by exposure category, while there was a strong tendency for more rapid development in older subjects for all three groups. This supports the view that external cofactors do not play major role in AIDS pathogenesis but that age is of fundamental importance.

A meta-analysis of estimates of the AIDS incubation distribution

Information from 12 studies is combined to estimate the AIDS incubation distribution with greater precision than is possible from a single study. The analysis uses a hierarchy of parametric models based on a four-parameter generalized F distribution. This general model contains four standard two-parameter distributions as special cases. The cases are the Weibull, gamma, log-logistic, lognormal distributions. These four special cases subsume three distinct asymptotic hazard behaviors. As time increases beyond the median of approximately 10 years, the hazard can increase to infinity (Weibull), can plateau at some constant level (gamma), or can decrease to zero (log-logistic and lognormal). The Weibull, gamma and 'log-logistic distributions' which represent the three distinct asymptotic hazard behaviors, all fit the data as well as the generalized F distribution at the 25 percent significance level. Hence, we conclude that incubation data is still too limited to ascertain the specific hazard assumption that should be utilized in studies of the AIDS epidemic. Accordingly, efforts to model the AIDS epidemic (e.g., back-calculation approaches) should allow the incubation distribution to take several forms to adequately represent HIV estimation uncertainty. It is recommended that, at a minimum, the specific Weibull, gamma and log-logistic distributions estimated in this meta-analysis should all be used in modeling the AIDS epidemic, to reflect this uncertainty.

Why prescribe highly purified factor VIII and IX concentrates?

The aftermath of the HIV catastrophe and hepatitis virus transmission to hemophiliacs has been characterized by continuous efforts to improve the purity of factor VIII and factor IX concentrates, increasing sophistication of the virucidal methods used, and the introduction of recombinant factor VIII. The cost of hemophilia care is substantial and there is a large price difference between products depending on their purity; generally, the purer the concentrate, the higher the price. The use of expensive highly purified concentrates may be questioned if these products are not superior in terms of safety, efficacy or convenience. The properties of concentrates used in hemophilia care are discussed in this review, as are their safety and side effects. The available data do not clearly reveal any clinical difference between factor VIII concentrates, although the highly purified products may be of theoretical benefit. With regard to factor IX, purified products do not seem to carry any risk of the well-known thromboembolic complications which occur in certain situations after treatment with prothrombin complex concentrates.

Five myths about AIDS that have misdirected research and treatment

A number of widely repeated and factually incorrect myths have pervaded the AIDS research literature, misdirecting research and treatment. Five of the most outstanding are: 1) that all risk groups develop AIDS at the same rate following HIV infection; 2) that there are no true seroreversions following HIV infection; 3) that antibody is protective against HIV infection; 4) that the only way to treat AIDS effectively is through retroviral therapies; and 5) that since HIV is so highly correlated with AIDS incidence, it must be the sole necessary and sufficient cause of AIDS. A huge body of research, reviewed in this paper, demonstrates the falsity of these myths. 1) The average number of years between HIV infection and AIDS is greater than 20 years for mild hemophiliacs, 14 years for young severe hemophiliacs, 10 years for old severe hemophiliacs, 10 years for homosexual men, 6 years for transfusion patients of all ages, 2 years for transplant patients, and 6 months for perinatally infected infants. These differences can only be explained in terms of risk-group associated cofactors. 2) Seroreversions are common. Between 10 and 20 percent of HIV-seronegative people in high risk groups have T-cell immunity to HIV, and may have had one or more verified positive HIV antibody tests in the past. 3) Antibody, far from being protective against HIV, appears to be highly diagnostic of loss of immune regulation of HIV, and some evidence of antibody-enhancement of infection exists. 4) Non-retroviral treatments of HIV infection, including safer sex practices, elimination of drug use, high nutrient diets, and limited reexposure to HIV and its cofactors have proven to be effective means of preventing or delaying onset of AIDS. 5) Many immunosuppressive factors, including drug use, multiple concurrent infections, and exposure to alloantigens, are as highly correlated with AIDS risk groups as HIV. These data are more consistent with AIDS being a multifactorial or synergistic disease than a monofactorial one.

The effect of covariates on the induction time of AIDS using improved imputation of exact seroconversion times

This paper explores the effects of covariates such as age, gender, chronological time of seroconversion, and mode of virus transmission on the interval between HIV seroconversion and the development of AIDS. For many cohorts which are available to provide information about such effects, both the time of seroconversion and the time of onset of AIDS may be right- or interval-censored. To analyse these doubly-censored data, we propose a method in which we first estimate the marginal distribution of the chronological time of seroconversion and use this distribution to impute the seroconversion time for each subject. Subsequently, we estimate the distribution of induction times conditional on the seroconversion distribution. We apply this technique to a cohort of HIV seropositive subjects recruited from various outpatient facilities throughout Italy and show that age at seroconversion has the greatest effect on induction time.

Non-parametric analysis of transfusion-related HIV and AIDS incidence data

The method for making non-parametric inferences about the probability distribution of the incubation period for AIDS from transfusion-related AIDS data is extended to include data on individuals who have tested positive for HIV but do not have AIDS at the time of analysis. The method is illustrated with data on individuals infected by transfusion in Australia. The shape of the incubation distribution, as represented by the truncated distribution function, can be estimated, but the additional data contribute very little to the estimation of this shape. With a general non-parametric form for the incubation distribution the additional data do not overcome the identifiability problem that exists for non-parametric estimation of this distribution from AIDS data alone. If quarterly rates for HIV testing are specified, the additional data make it possible to estimate the cumulative distribution function for the incubation period. This is also possible when a simple parametric form, with one or two unknown parameters, is used for the testing rates. However, the additional data do not allow effective estimation of the HIV testing rates. The estimated shape of the incubation distribution indicates a higher proportion of short incubation periods than an earlier estimate based on U.S. data. Estimates for the incubation distribution itself do not vary much over a plausible range of HIV testing rates.

HIV infection and surgeons

The human immunodeficiency virus (HIV) causes acquired immunodeficiency syndrome, which remains uniformly fatal in affected individuals. A common route of HIV transmission is via inoculation of contaminated blood, which may occur during surgical procedures. Surgeons may estimate their risk of HIV infection over a 30-year surgical career based on HIV prevalence among surgical patients, percutaneous injury rate per operation, and seroconversion rate. Surgeons can reduce their risk by various means, but the most pragmatic is by reducing the rate of percutaneous injury through optimal surgical technique and proper precautions.

A new approach to estimating AIDS incubation times: results in homosexual infected men

STUDY OBJECTIVE

The aim was to develop a new approach for estimating the incubation period of acquired immunodeficiency syndrome (AIDS), based on age distributions.

DESIGN

Incubation period was expressed as the difference between age at time of diagnosis and age at time of contamination. Assuming independence between age at time of infection and incubation period, the age distribution of newly diagnosed AIDS cases is thus the convolution product between the distributions of the age of freshly infected patients and of the incubation times. AIDS incubation time can therefore be estimated from the age distribution of newly HIV infected subjects and newly diagnosed AIDS cases.

SUBJECTS

Subjects were 2220 AIDS cases diagnosed until 1987, reported to the Ministry of Health, France, and 172 subjects discovered to be HIV-1 seropositive during a blood donation in Paris between August 1985 and July 1988. In both groups, the only known risk factor was homosexuality.

MAIN RESULTS

The estimated median incubation time was 9.9 years (90% CI 9.0-10.9 years). Confidence intervals were narrow, even when taking into account the uncertainty in serodetection delay (90% CI 6.7-13.5 years).

CONCLUSIONS

The incubation estimate is as accurate as previous estimates based on other models. This technique could therefore be applied to other risk groups.

Intravenous immunoglobulin in HIV-I infected haemophilic patients

In order to evaluate the efficacy of intravenous immunoglobulin (IVIG) in the early stages of HIV infection (patients without AIDS or AIDS related complex) a prospective controlled open trial was conducted in 36 patients (age 6-19 years) with haemophilia. Eighteen patients received 0.3 g/kg IVIG at two week intervals; 18 patients served as controls. Major criteria for the evaluation were progression of HIV disease assessed by the modified Brodt/Helm classification, number of infectious events and HIV associated thrombocytopenia, and the CD4+ T cell count. After 24 months of evaluation seven patients in the IVIG group and five patients in the control group deteriorated according to their staging, with one patient in each group developing AIDS. Thrombocytopenia and infectious events, but no severe bacterial infections, occurred in both groups in similar numbers. The absolute CD4+ T cell count decreased by 284/microliters in the IVIG group and by 143/microliters in the control group respectively (mean values). The statistical analysis of these criteria did not reveal any significant difference. In conclusion, IVIG was not effective in the early stages of HIV infection in patients with haemophilia. IVIG did not slow down the progression of HIV disease and did not prevent the development of an immunodeficiency as assessed by the CD4+ T cell count.

Effects of different parametric estimates of seroconversion time on analysis of progression to AIDS among Italian HIV-positive haemophiliacs

The purpose of this study was to estimate seroconversion time using different parametric methods and to assess their influence on the estimation of the incubation time between HIV infection and onset of AIDS. Study subjects were 712 HIV-positive haemophiliacs enrolled in the Italian National Registry of patients with congenital coagulation disorders. Seroconversion time was estimated using the mid-point of each seroconversion interval (MID), the median of each interval under an estimated uniform distribution with cutpoints at December 1981 and December 1985 (MUU), the median of each interval under an estimated Weibull distribution (MUW), and the median of three random values drawn from each interval under the Weibull distribution (RUW). Kaplan-Meier survival analysis showed that the cumulative incidence of AIDS over a 7-year period was 11.6 per cent (SE 1.3 per cent) when using the MID estimate of seroconversion time, 10.8 per cent (1.2 per cent) with the MUU estimate, and 13.4 per cent (1.3 per cent) and 12.3 per cent (1.3 per cent) when using MUW and RUW estimates, respectively. This study demonstrates that the estimate of seroconversion time does not seem to be a major factor affecting estimates of AIDS incidence since the different techniques for estimating HIV seroconversion time yielded very similar results.

Progression of HIV disease in a haemophilic cohort followed for 11 years and the effect of treatment

OBJECTIVE

To describe the progression of HIV disease in a haemophilic cohort and to show the influence of treatment.

DESIGN

11 year longitudinal clinical and laboratory study.

SETTING

A haemophilia centre.

PATIENTS

111 patients infected with HIV during October 1979 to July 1985.

MAIN OUTCOME MEASURES

Symptoms of HIV infection, AIDs, and death.

INTERVENTIONS

26 asymptomatic patients started taking zidovudine or placebo (1000 mg/day) during November 1988 to February 1990; 10 patients with CD4+ counts of 0.2 x 10(9)/l started zidovudine 500 mg/day during January to November 1990. 35 patients used pentamidine for primary or secondary prophylaxis.

RESULTS

At 11 years from seroconversion the estimated rate of progression to AIDS was 42% (95% confidence interval 27% to 57%); to symptoms 85% (75% to 95%); and to death 41% (25% to 57%). Progression to AIDS was significantly faster in patients aged 25 and over than in those aged less than 25 (relative risk 5.0 (2.4 to 10.4); p less than 0.00001) and in those with previous cytomegalovirus infection than in those not infected (relative risk 3.0 (1.4 to 6.8); p = 0.006). 16 of 27 (59%) patients with p24 antigenaemia developed AIDS compared with 17 of 84 (20%) patients without p24 antigen (p less than 0.001). The risk of progression to AIDS before 30 November 1988 in patients with CD4+ counts less than or equal to 0.2 x 10(9)/l was higher than after November 1988 (relative risk 1.9 (0.85 to 4.43); p = 0.1). For 1989 and 1990 the observed cumulative numbers of AIDS cases (among 81 patients with sufficient CD4+ counts) were 22 and 25 compared with 29 and 37 predicted from the rate of fall of CD4+ counts up to the end of 1988 (p = 0.03).

CONCLUSION

Treatment seems to be reducing the progression of HIV disease in this haemophilic cohort.

The spread of HIV-1 in Africa: sexual contact patterns and the predicted demographic impact of AIDS

The spread of HIV-1 in Africa is examined here in the light of recent information on the main epidemiological and behavioural determinants of transmission. Mathematical models incorporating demographic, epidemiological and behavioural processes are used to assess the potential demographic impact of the disease AIDS. These analyses highlight the significance of patterns of sexual behaviour, and in particular networks of sexual contact, on the predicted spread of infection. Current data reveal substantial variations in the degree of spread between and in countries, but new analyses support earlier predictions that in the worst-afflicted areas AIDS is likely to change population growth rates from positive to negative values in a few decades.

A prospective study of 115 initially asymptomatic HIV infected gay men in Stockholm, Sweden

A cohort of 115 asymptomatic gay men, all seropositive for HIV, was recruited in a health screening project in Stockholm, Sweden, between Nov. 1982 and Dec. 1983 and subsequently followed and clinically evaluated after a mean observation time of 63 months. AIDS in accordance with the surveillance definition (CDC group IV C-1 and D) developed in 34 (29.6%) of the men, while 1 (0.9%) additional man died of multiple myeloma classified as CDC group IV E. Constitutional symptoms (CDC group IV A) developed in 13 (11.3%) men, while symptoms from the central nervous system classified as CDC group IV B occurred in 1 (0.9%) additional man. Minor opportunistic infections included in the definition for CDC group IV C-2 developed in 12 (10.4%) men, while 48 (41.7%) men remained asymptomatic, with or without persistent generalized lymphadenopathy (PGL). One man who died of AIDS had been treated for malignant melanoma (MM) and one who did not fulfill the criteria for CDC group IV died of MM during the observation period. The 5-year actuarial progression rate to surveillance defined AIDS was 31.5% and to CDC group IV 53.6%. No statistically significant association was found between disease progression and a number of recorded epidemiological variables, most previous and present sexually transmitted diseases (STD) (except gonorrhoea) and the presence of PGL at entry. On the other hand, reduced delayed cutaneous hypersensitivity, in particular to tuberculin, as well as the presence of a high IgG titer against cytomegalovirus (CMV), were correlated to disease progression.

HIV-1 infection in a cohort of haemophilic patients

The course of HIV infection in 53 haemophilic patients aged 5-20 years was evaluated by clinical examination and laboratory tests. During the evaluation time (median 30 months) two patients died of AIDS and 32 patients (60%) deteriorated when assessed by the Brodt-Helm classification. Nineteen patients (37%) had decreased absolute helper cell counts (less than 500 CD4 positive cells/microliters), and 45 patients (87%) had reduced helper cell to lymphocyte ratios (less than 0.35). HIV-1 was isolated from peripheral lymphocytes in 29 of 46 patients. As the disease progressed the number of positive viral cultures increased. Considerable progression of the HIV infection was seen in haemophilic children and adolescents during the median evaluation period of 30 months. The transition from symptomless HIV infection to immunodeficiency was easily recognised. A lowered ratio of helper cells to lymphocytes seems to be a useful marker of the beginning of the deterioration of the immune system.

Course of HIV-I infection in a cohort of homosexual and bisexual men: an 11 year follow up study

OBJECTIVE--To characterise the natural history of sexually transmitted HIV-I infection in homosexual and bisexual men. DESIGN--Cohort study. SETTING--San Francisco municipal sexually transmitted disease clinic. PATIENTS--Cohort included 6705 homosexual and bisexual men originally recruited from 1978 to 1980 for studies of sexually transmitted hepatitis B. This analysis is of 489 cohort members who were either HIV-I seropositive on entry into the cohort (n = 312) or seroconverted during the study period and had less than or equal to 24 months between the dates of their last seronegative and first seropositive specimens (n = 177). A subset of 442 of these men was examined in 1988 or 1989 or had been reported to have developed AIDS. MAIN OUTCOME MEASURES--Development of clinical signs and symptoms of HIV-I infection, including AIDS, AIDS related complex, asymptomatic generalised lymphadenopathy, and no signs or symptoms of infection. MEASUREMENTS AND MAIN RESULTS--Of the 422 men examined in 1988 or 1989 or reported as having AIDS, 341 had been infected from 1977 to 1980; 49% (167) of these men had died of AIDS, 10% (34) were alive with AIDS, 19% (65) had AIDS related complex, 3% (10) had asymptomatic generalised lymphadenopathy, and 19% (34) had no clinical signs or symptoms of HIV-I infection. Cumulative risk of AIDS by duration of HIV-I infection was analysed for all 489 men by the Kaplan-Meier method. Of these 489 men, 226 (46%) had been diagnosed as having AIDS. We estimated that 13% of cohort members will have developed AIDS within five years of seroconversion, 51% within 10 years, and 54% within 11.1 years. CONCLUSION--Our analysis confirming the importance of duration of infection to clinical state and the high risk of AIDS after infection underscores the importance of continuing efforts both to prevent transmission of HIV-I and to develop further treatments to slow or stall the progression of HIV-I infection to AIDS.

Susceptibility to HIV infection and AIDS in Italian haemophiliacs is HLA associated

We compared the frequencies of HLA antigens in two matched groups of 31 HIV-seronegative and 31 HIV-seropositive haemophiliacs, exposed during the years 1981-85 to comparable amounts and batches of presumably infectious clotting factor concentrates. The frequency of A2 was significantly higher in HIV-seropositive than in seronegative haemophiliacs, with a relative risk (RR) of seroconversion of 3.92, whereas both Bw52 and DR4 were negatively associated with it. We also studied the distribution of HLA antigens in a larger group of 76 HIV-seropositive haemophiliacs, who were at different clinical stages of HIV infection (CDC classes II-IV) but were comparable for age and time elapsed since seroconversion. DR3 and DQw2 antigens were, particularly when concomitantly present, associated with a high risk of developing symptomatic HIV infection (RR = 11.79 and 25.33). Our data suggest that the HLA region controls susceptibility to infection with HIV and its progression to symptomatic disease in Italian haemophiliacs.

The natural history of human immunodeficiency virus infection: a five year study in a London cohort of homosexual men

Progression rates from asymptomatic to symptomatic Human Immunodeficiency Virus (HIV) infection according to the CDC classification were prospectively studied in a cohort of 172 seropositive homosexual and bisexual men. The median follow-up time was 4 years. The progression from data of entry to the study to any group IV disease was 56% (SE 7%) at 5 years. However, the progression from an estimated date of seroconversion to any group IV disease was 36% (SE 4%) at 5 years. This was more than double the progression rate to AIDS-14% (SE 3%) at 5 years calculated in the same way. There were no differences in progression to AIDS from group IV A (systemic symptoms such as unexplained fever, weight loss or persistent diarrhoea) and group IV C-2 (oral candida or oral hairy leukoplakia). Progression rates to AIDS were significantly lower (p = 0.02) in patients who were under 25 years of age at entry than in those over 25. A review of progression rates to AIDS among homosexual cohorts shows that they tend to be higher than in cohorts of haemophiliac patients, in the early stage of infection. However, when Pneumocystis carinii pneumonia is the outcome measure, progression rates in all studies are remarkably similar.

Time from infection with HIV to onset of AIDS in patients with haemophilia in the UK

The two-stage parametric regression model of Brookmeyer and Goedert has been adapted and fitted to data on the development of AIDS in haemophiliacs in the UK who are seropositive for HIV. The risk of developing AIDS by a given time following seroconversion increases with increasing age at seroconversion. It is likely that the risk increases smoothly with age, although the data have been analysed in three age categories, and it is estimated that by seven years after seroconversion 6 per cent of patients aged under 25 at seroconversion, 20 per cent of those aged 25-44 and 34 per cent of those aged 45 or more have developed AIDS. For a given age at seroconversion the annual risk of developing AIDS increases with increasing time after seroconversion, and at seven years the annual risks of developing AIDS during the next year in the three age groups are estimated to be 2 per cent for those aged less than 25 at seroconversion, and 10 and 11 per cent respectively for those aged 25-44 and 45 or more.

Estimating the distribution of times from HIV seroconversion to AIDS using multiple imputation. Multicentre AIDS Cohort Study

Multiple imputation is a model based technique for handling missing data problems. In this application we use the technique to estimate the distribution of times from HIV seroconversion to AIDS diagnosis with data from a cohort study of 4954 homosexual men with 4 years of follow-up. In this example the missing data are the dates of diagnosis with AIDS. The imputation procedure is performed in two stages. In the first stage, we estimate the residual AIDS-free time distribution as a function of covariates measured on the study participants with data provided by the participants who were seropositive at study entry. Specifically, we assume the residual AIDS-free times follow a log-normal regression model that depends on the covariates measured at enrolment on the seropositive participants. In the second stage we impute the date of AIDS diagnosis for the participants who seroconverted during the course of the study and are AIDS-free with use of the log-normal distribution estimated in the first stage and the covariates from each seroconverter's latest visit. The estimated proportions developing AIDS within 4 and within 7 years of seroconversion are 15 and 36 per cent respectively, with associated 95 per cent confidence intervals of (10, 21) and (26, 47) per cent. We discuss the Bayesian foundations of the multiple imputation technique and the statistical and scientific assumptions.

Risk of AIDS in HIV seroconverters: a comparison between intravenous drug users and homosexual males

A multicentre cohort study was conducted in Italy to estimate the risk of developing AIDS in 261 intravenous drug users and 89 homosexual males for whom the seroconversion period was known. Four years after HIV seroconversion, AIDS incidence, estimated by Kaplan-Meier survival technique, was 13.8% for intravenous drug users and 16.2% for homosexual males; the difference was not statistically significant. These findings suggest that four years after seroconversion the risk of developing AIDS in HIV seropositive intravenous drug users is no higher than that of subjects who acquired HIV infection through sexual contact.

Incubation time of AIDS: progression of disease in a cohort of HIV-infected homo- and bisexual men with known dates of infection

The time from infection with HIV to symptoms and AIDS is an important parameter in describing the natural course of HIV infection. We here describe disease progression in a group of 389 homo- and bisexual men. Of these 102 had known dates of infection, and during an average follow-up time of 31 months (range 2-108), 28 of these progressed from being symptom-free (CDC group II and III) to having some symptom from CDC group IV; 7 progressed to AIDS. By life-table analysis, the estimated average time from seroconversion to first symptom is approximately 5 years and to AIDS approximately 8 years. Very few patients are diagnosed with AIDS the first 2 years after infection, but after that the risk seems to be 5-10% per year. Increasing use of anti-HIV medication will render studies of this kind difficult in the future.

HIV-1 infection in haemophilia

Guidelines have been prepared by the National Hemophilia Foundation, USA, for treating patients with haemophilia, these are: 1. General recommendations. The risks of withholding treatment far outweigh risks of treatment. Patients should however be educated to use appropriate clotting factor doses to minimize overuse and contain costs. 2. Factor VIIIC-deficient patients. DDAVP should be used whenever possible by patients with mild or moderate factor VIIIC deficiency. When feasible, an alternative to concentrates may be the use of cryo-precipitate prepared from one well-screened donor or from a small number of such donors. (a) Prevention of hepatitis. Hepatitis B vaccination is essential for uninfected patients. Preliminary data suggest that products that are pasteurized, solvent/detergent-treated or monoclonal antibody-purified are at a reduced risk of transmitting hepatitis viruses. (b) Prevention of HIV-1. Concentrates pasteurized, treated with solvent/detergent, purified with monoclonal antibody, heated in suspension with organic solvents, or dry heat-treated for long periods are preferred. These products carry a substantially reduced risk of transmitting HIV-1. 3. Factor IX deficiency. For patients with severe deficiency the use of virus-inactivated Factor IX concentrate is recommended. For mild to moderate patients when feasible an alternative would be fresh, frozen plasma prepared from one well-screened and repeatedly-tested donor or from a small number of such donors. In the past few years, significant progress has been made in understanding the nature of the defect in haemophilia both at the molecular and structural levels, such a foundation is necessary for definitive treatments in the future. For now, however, the dark side of replacement therapy must be accepted along with its benefits.

The natural history of transfusion-associated infection with human immunodeficiency virus. Factors influencing the rate of progression to disease

Patients infected by the human immunodeficiency virus (HIV) as a result of blood transfusions are unique in that their dates of infection are well defined and their medical conditions before infection are known. To characterize the natural history of transfusion-associated HIV infection, we studied 694 recipients of blood from 112 donors in whom AIDS later developed and from 31 donors later found to be positive for HIV antibody. Of the recipients tested, 85 were seronegative, 116 were seropositive, and 19 had AIDS. Of 101 HIV-seropositive recipients followed for a median of 55 months after infection, 54 had Centers for Disease Control Class IV disease, including 43 with AIDS. Life-table analysis suggested that AIDS will develop in 49 percent of infected recipients (95 percent confidence limits, 36 to 62 percent) within seven years after infection. As compared with recipients without AIDS, the 43 recipients with AIDS had received more transfusions at the time of infection (median, 21 vs. 7; P = 0.01). HIV-infected blood donors in whom AIDS developed were grouped according to whether AIDS developed within 29 months (the median) after donation (Group 1) or 29 or more months after donation (Group 2). As compared with the 31 recipients of blood from Group 2 blood donors, the 31 recipients of blood from Group 1 donors were more likely to have AIDS four years after infection (49 percent vs. 4 percent; P = 0.005) and illnesses resembling acute retroviral syndrome (14 of 24 vs. 5 of 22; P = 0.03). We conclude that most recipients of HIV-infected blood become seropositive, that AIDS develops in about half these recipients within seven years, and that the risk may be higher when AIDS develops in the blood donor soon after donation.

The natural history of human immunodeficiency virus infection in a haemophilic cohort

112 haemophilic patients infected with HIV were followed up with clinical and laboratory assessment between 1 December 1979 and 30 November 1988. Sixty-six (59%) of the patients developed HIV-related clinical symptoms and 22 (20%) developed AIDS. Twenty (18%) of the patients developed p24 antigenaemia. Amongst the 59 patients whose date of seroconversion could be estimated the calculated 8-year cumulative incidence of AIDS was 40% (symptoms 73%). For the whole cohort of 112 patients, the median slope of linear regression of the absolute T4 lymphocyte count was steeper for those with AIDS (-0.113 x 10(9)/l per year) than for those without AIDS (-0.054 x 10(9)/l per year) (P less than 0.02). While 15 cases of AIDS developed during 58 patient-years of follow up after falling below a T4 lymphocyte count of 0.2 x 10(9)/l, only two cases occurred during 450 patient-years before reaching this count. Thus the decline of the T4 lymphocyte count to 0.2 x 10(9)/l may be an appropriate additional end-point for the assessment of new treatments for asymptomatic patients infected with HIV.

Estimation of the incidence of HIV infection

The aim of the method of 'back projection' is to provide estimates of the number of new infections with the human immunodeficiency virus (HIV) as a function of time, by using the numbers of diagnoses of the acquired immune deficiency syndrome (AIDS) together with information on the distribution of the incubation period between infection and diagnosis. Here, the method is investigated with particular reference to cases of HIV infection and AIDS in the United Kingdom.

Incidence of AIDS and excess of mortality associated with HIV in haemophiliacs in the United Kingdom: report on behalf of the directors of haemophilia centres in the United Kingdom

OBJECTIVE--To estimate the cumulative incidence of AIDS by time since seroconversion in haemophiliacs positive for HIV and to examine the evidence for excess mortality associated with HIV in those who had not yet been diagnosed as having AIDS. DESIGN--Analysis of data from ongoing national surveys. SETTING--Haemophilia centres in the United Kingdom. PATIENTS--A total of 1201 men with haemophilia who had lived in the United Kingdom during 1980-7 and were positive for HIV. INTERVENTION--None. END POINTS--Diagnosis of AIDS; death in those not diagnosed as having AIDS. MEASUREMENTS AND MAIN RESULTS--Estimation of cumulative incidence of AIDS and number of excess deaths in seropositive patients not diagnosed with AIDS. Median follow up after seroconversion was 5 years 2 months. Eight five patients developed AIDS. Cumulative incidence of AIDS five years after seroconversion was 4% among patients aged less than 25 at first test positive for HIV, 6% among those aged 25-44, and 19% among those aged greater than or equal to 45. There was little evidence that type or severity of haemophilia or type of factor VIII or IX that had caused HIV infection affected the rate of progression to AIDS. Mortality was increased among those who had not been diagnosed as having AIDS, especially among those with "AIDS related complex." Thirteen deaths were observed among 36 patients diagnosed as having AIDS related complex against 0.65 expected, and 34 deaths in 1080 other patients against 22.77 expected; both calculations were based on mortality rates observed in haemophiliacs in the United Kingdom in the late 1970s. CONCLUSIONS--Rate of progression to AIDS depended strongly on age. There is a substantial burden of fatal disease among patients positive for HIV who have not been formally diagnosed as having AIDS.

Safety of blood and blood products in Scandinavia today

The safety of blood and blood products in Scandinavia today is high. An absolutely safe blood supply is, however, an unattainable goal. The dominating risk is transmission of non-A, non-B virus (NANBV). The calculated per blood unit risk is 1:200. The incidence of cirrhosis due to post-transfusion hepatitis NANB is calculated to at most 0.1% among recipients of blood components from about 5 donors. Other risk factors are transmission of hepatitis B virus (HBV), human immunodeficiency virus (HIV-1) and cytomegalovirus (CMV). The prevalence of HBsAg among first time donors is about 0.05% (Sweden). In Scandinavia, anti-HIV-1 has been found in 0.001% of donations from start of screening in 1985 to December 1987. The prevalence was higher in Denmark, lower in Finland (and perhaps Iceland). The prevalence has declined during the last years. As of June 1988, 117 patients in the Scandinavian countries have been infected by blood components, all but 2 before screening was introduced. Besides these, 226 haemophiliacs have been infected by, in almost all cases, imported clotting factor concentrates before heat treatment was introduced. Most of the infected patients are still asymptomatic. About 70% of blood donors have anti-CMV, a few percent of which will transmit CMV-infection, with severe symptoms, to immunosuppressed patients without anti-CMV.