A model-based approach to characterize the incubation period of paediatric transfusion-associated acquired immunodeficiency syndrome

Traditional statistics, such as the average, currently provide a misleading statistical description of the incubation periods of paediatric transfusion-associated acquired immunodeficiency syndrome (TA-AIDS). Two types of length-biased sampling, left censoring and right censoring, occur in the 37 cases diagnosed before 1986 and reported to the Centers for Disease Control by 15 September 1986. To correct for these problems, we propose a truncated Weibull distribution with use of a maximum likelihood technique. This approach suggests that the mean incubation period of paediatric TA-AIDS cases is 2.4 years with a 90 per cent confidence interval ranging from 1.5 years to 7.2 years. The mode is 1.25 years. These estimates are much shorter than those recently published for adults, therefore the success of TA-AIDS prevention strategies may be seen sooner in the paediatric age group.

Transmission of human immunodeficiency virus (HIV) by blood transfusions screened as negative for HIV antibody

Since early 1985, blood donations in the United States have been screened for antibody to human immunodeficiency virus (HIV). To identify instances of HIV transmission by antibody-negative donations, we investigated 13 persons seropositive for HIV who had received blood from 7 donors who were screened as negative for HIV antibody at the time of donation. Twelve of the 13 recipients had no identifiable risk factors for HIV infection other than the transfusions they had received. On evaluation 8 to 20 months after transfusion, HIV-related illnesses had developed in three recipients, and the acquired immunodeficiency syndrome had developed in one. All seven donors were found to be infected with HIV. On interview, six reported a risk factor for HIV infection, and five had engaged in high-risk activities or had had an illness suggestive of acute retroviral syndrome within the four months preceding their HIV-seronegative donation. Thus, these donors had apparently been infected only recently, and so were negative at the time of blood donation according to available antibody tests. We conclude that there is a small but identifiable risk of HIV infection for recipients of screened blood. To minimize this risk, the reasons for deferral of donation need to be communicated more effectively to blood donors who are at high risk of HIV infection, and new assays that detect HIV infection earlier should be evaluated for their effectiveness in screening donated blood.

Risk of human immunodeficiency virus transmission from heterosexual adults with transfusion-associated infections

The risk of human immunodeficiency virus (HIV) transmission was studied by interviewing and testing the serum of heterosexual contacts and casual family contacts of adults with transfusion-associated HIV infections. Two (8%) of 25 husbands and ten (18%) of 55 wives who had had sexual contact with infected spouses were seropositive for HIV. Compared with seronegative wives, the seropositive wives were older (median ages, 54 and 62 years; P = .08) and actually reported somewhat fewer sexual contacts with their infected husbands (means, 156 and 82; P greater than .1). There was no difference in the types of sexual contact or methods of contraception of the seropositive and seronegative spouses. There was no evidence of HIV transmission to the 63 other family members. Although most husbands and wives remained uninfected despite repeated sexual contact without protection, some acquired infection after only a few contacts. This is consistent with an as yet unexplained biologic variation in transmissibility or susceptibility.

Twin study of genetic and environmental effects on lipid levels

A study of 106 pairs of monozygotic (MZ) and 94 pairs of dizygotic (DZ) twins tested the hypothesis that part of the previously described genetic influence on blood lipid levels can be ascribed to closer similarities among MZ than among DZ twin pairs in environmental factors that affect lipid levels. Participants were adult twin volunteers (age 17-66; 64 male and 136 female pairs) who were selected from the NH & MRC Twin Registry or were respondents to advertisements. They completed a 4-day weighed food diary from which mean nutrient intake was derived. Information on lifestyle and demographic variables was obtained by questionnaire and a nonfasting blood sample was taken for measures of total, low-density lipoprotein (LDL) cholesterol, and high-density lipoprotein (HDL) cholesterol and the HDL2 and HDL3 subfractions. Height and weight were measured, and body mass index (BMI) was calculated (kg/m2). Estimates of the heritability of sex-adjusted lipid levels were 0.72 for total cholesterol, 0.79 for HDL cholesterol, 0.69 for HDL2, 0.20 for HDL3, 1.06 for LDL cholesterol, and 0.44 for sex-adjusted BMI. In all cases except for HDL3, genetic variance was statistically significant. After adjusting for the effects of environmental variables in three different ways, the estimates of heritability were somewhat lower for total cholesterol, HDL2, and BMI, and those for HDL cholesterol (borderline) and LDL cholesterol (definitely) remained statistically significant but were decreased. A genetic influence on HDL3 was not found. Adjusted heritability estimates obtained from one method of analysis were 0.35 for total cholesterol, 0.49 for HDL, 0.04 for HDL2, -0.34 for HDL3, 0.66 for LDL, and 0.32 for BMI. These results suggest that the assumptions made in the classical twin study approach are not appropriate when examining genetic effects on lipid levels or BMI, or indeed on any biological variable that may be affected by environmental factors that tend to be more similar in MZ twins than in DZ twins. In these circumstances, more complex models may be needed to differentiate between genetic and environmental influences.

Lifestyle factors in monozygotic and dizygotic twins

In examining genetic influences on biological variables using twins, it may be important to examine the distribution between and within twin pairs of demographic and lifestyle factors that may themselves affect the biological variable being studied. We explored the distribution of demographic and lifestyle factors that may affect blood lipid levels or ischaemic heart disease (IHD) risk among a sample of 106 monozygotic (MZ) and 94 like-sex dizygotic (DZ) twin pairs. In our sample, MZ twins were statistically significantly different from DZ twins only in marital status, cigarette smoking habits, and the ratio of polyunsaturated to saturated fat (P:S ratio) in their dietary intake. The latter variable was among many dietary variables examined (using 4-day weighed food diaries), and the size of the difference in intake was small. When comparisons were made of the similarities within twin pairs, we found members of MZ twin pairs to be statistically significantly closer than DZ twins in educational achievement, occupation, cigarette smoking, and exercise habits, and the number of days a week on which alcohol was consumed. These last three variables were consistently closer among twins with closer contact than among those with a smaller degree of current shared environment. For 12 of the 13 nutrients examined, the within-pair correlations were higher for MZ than for DZ twins, although our test for significant genetic variance showed statistical significance only for intake of complex carbohydrates. We conclude that MZ twins share demographic and lifestyle factors that might influence the risk of IHD and blood lipid levels to a greater degree than do DZ twins, although it is difficult to say if these similarities in lifestyle result from genetic influences or not. Nevertheless, ascribing differences between correlations in MZ and DZ twin pairs for lipid levels as being purely "genetic"--as implicit in conventional measures of heritability--is likely to overestimate the influence of genetic factors.

Risk of AIDS for recipients of blood components from donors who subsequently developed AIDS

Reported cases of acquired immunodeficiency syndrome (AIDS) in San Francisco as of March 31, 1986, include 92 individuals who had donated blood subsequent to 1978. Their donated blood components had been transfused into 406 different recipients. The current status of 336 of these recipients was ascertained as of April 1, 1986. Of these, 223 had died at the time of our first contact, almost all as a result of the condition for which they were transfused. Seven had developed AIDS; five of these died, two before entry into the study and three subsequently. Forty-six additional living recipients were interviewed and evaluated. Seven had the AIDS-related complex, 18 had antibody to the human immunodeficiency virus (HIV) but were otherwise healthy, and 19 had no detectable anti-HIV. Two had risk factors other than transfusion. The frequency of infection of the recipient decreased as the time interval between transfusion and the diagnosis of AIDS in the donor increased. This information should be useful when counseling patients who have been transfused with blood components from donors later found to be infected with HIV.

Estimating the risks of transfusion-associated acquired immune deficiency syndrome and human immunodeficiency virus infection

The risk of transfusion-associated acquired immunodeficiency syndrome (AIDS) has been difficult to estimate because of the long and variable incubation period. Mathematical modeling suggests there may eventually be 2100 cases among persons aged 13 to 65 who received transfusions between 1978 and 1984. An estimated 12,000 living transfusion recipients of all ages from these years are infected with the human immunodeficiency virus, the virus that causes AIDS. Secondary transmission might be prevented by testing and counseling recipients, but the likelihood of infection in any single recipient is small.

Association of eosinophilic myositis with an unusual species of Sarcocystis in a beef cow

The carcass of a mature cow had numerous, disseminated lesions typical of eosinophilic myositis. To elucidate the nature and possible cause of the lesions, histological sections were examined by light microscopy and selected areas were removed and processed for electron microscopy. The lesions were granulomatous in nature. Each granuloma contained at its centre an intact or ruptured sarcocyst associated with degenerate muscle fibers. Surrounding this was a layer of epithelioid cells and an intense accumulation of inflammatory cells, most of which were eosinophils. The primary cyst wall of the sarcocysts in these granulomas consisted of hair-like protrusions that featured many unusual electron-dense bodies. Sarcocysts with ultrastructures characteristic of Sarcocystis cruzi and Sarcocystis hirsuta were also present in muscle from the same animal, but these sarcocysts lacked any associated cellular responses. The eosinophilic myositis in this case appeared to be associated with sarcocystosis of an unknown species. Possibly, the inflammatory reaction was due to the host-parasite interaction in an unusual host.

Isolation and characterization of salivary antigens from the female tick, Dermacentor andersoni

The salivary glands of ixodid ticks are complex organs which are known to contain the antigens responsible for tick resistance in animals. We have identified a large number of proteins from salivary gland extracts (SGE), at least some of which are immunologically recognized by tick resistant animals and which are therefore presumed to be secreted salivary components. During the 6 to 10 day feeding process, a number of these antigens alter in concentration according to individual kinetics, and some of these changes correlate with the kinetics of skin test reactivity of SGE obtained at different times throughout the feeding period. By use of immunoaffinity chromatography we have isolated large quantities of many of the salivary antigens (SGA) contained in SGE, and found that they contain several esterase activities. SGA stimulates both immediate and delayed skin reactions in tick resistant guinea-pigs, and these reactions are about 200-fold more intense, per unit protein, than those elicited by SGE. The skin reactions to SGA are basophil-mediated and have many features in common with the cutaneous basophil hypersensitivity reactions of tick resistant animals. The demonstrated antigenic complexity of the glands may have profound implications for attempts to develop anti-tick vaccines, as it may eventually be found that candidate vaccines will have to incorporate more than one tick antigen in order to be effective.

Laboratory and epidemiologic evaluation of an enzyme immunoassay for antibodies to HTLV-III

The enzyme immunoassays (EIAs) for antibody to human T-cell lymphotropic virus type III (HTLV-III) were rapidly adopted for screening donated blood and plasma. To evaluate the significance of a positive EIA reaction, test performance was examined in a blood bank screening program. Specimens were tested by EIA, Western blot assay, and HTLV-III/lymphadenopathy-associated virus (LAV) culture. The EIA was positive in 0.25% of 67 190 blood donations. Specimens were categorized and 57.3% had low (weak) reactivity, 12.7% had moderate reactivity, and 30.0% had high reactivity. Highly reactive specimens were strongly associated with a positive Western blot or culture (86.7%) in contrast to moderately and weakly reactive specimens (1.9%). Twenty-five of 29 donors interviewed with a highly reactive EIA had risk factors for HTLV-III/LAV infection. Risk factors were not identified for 74 of 75 interviewed donors with specimens of lower reactivity. The minimum calculated specificity was 99.82%. The use of the HTLV-III EIA has virtually eliminated the use of blood and plasma from HTLV-III/LAV infected donors.

Assessment of screening as a preventive technology: the example of HTLV-III/LAV antibody testing

Screening for disease control can be defined as a preventive technology that is used to examine asymptomatic people in order to classify them as likely or unlikely to have the disease that is the object of screening. Screening may consist of routine physical examinations, radiologic procedures, semi-invasive procedures such as endoscopy, or serologic tests. In this paper, a new serologic test is considered. Acquired immunodeficiency syndrome (AIDS) is a devastating disease with high mortality, recently shown to be caused by a retrovirus named human T-lymphotropic virus Type III (HTLV-III) or lymphadenopathy-associated virus HTLV-III antibody in serum specimens. Performance characteristics are excellent with high sensitivity and specificity when reactive serum specimens are checked for consistency of response by enzyme immunoassay (EIA). This test is now part of the screening protocol for all blood donation centers to decrease the risk of HTLV-III transmission via blood or blood products. About 0.2% (1 in 400) of blood donors have repeatedly reactive EIA tests to HTLV-III antibody. Approximately one-third of these donors have other laboratory evidence of infection. Screening for HTLV-III is a new technology that illustrates virtually all of the factors that need consideration in an assessment of disease screening. This paper explores these technical, epidemiologic, economic, legal, social, and ethical factors.

Are there compartment syndromes in some patients with idiopathic back pain?

Palpable rigidity of the epaxial (paraspinal) muscles, lordotic flattening, and spinal flexion accompanying back pain generally are ascribed to epaxial muscle spasm. However, palpable rigidity without muscle spasm occurs in compartment syndromes and epaxial muscle contractions extend the spine, increasing lordosis. Epaxial compartment syndromes are proposed as a possible cause of palpable rigidity, lordotic flattening, and spinal flexion accompanying idiopathic back pain. This article demonstrates the following: existence of an epaxial compartment by latex and dye injections; simulation of epaxial compartment syndromes in unembalmed cadavers by saline injections; and a "Bourdon tube effect" producing spinal flexion with lordotic flattening during epaxial compartment syndrome simulation in embalmed cadavers. In addition, resting and exercising epaxial compartment pressures were measured in 18 normal volunteers with a slit catheter.

Allogeneic bone marrow transplantation at Christchurch 1979-1985

Twelve bone marrow transplants have been carried out at Christchurch since 1979 in five patients with aplastic anaemia and seven with acute leukaemia. Five patients are currently alive at 77, 69, 63, 45, and seven months post-transplant. Acute and chronic graft versus host disease have been major problems and its clinical features and management are described. Long term follow-up data is presented on the four patients currently alive at between three to six years post-transplant. The practical problems we have experienced by carrying out bone marrow transplants without special funding have been considerable and the implications of this are discussed.