Prevalence of hepatitis C virus infection and risk for hepatocellular carcinoma and non-Hodgkin lymphoma in AIDS

Hepatitis C virus (HCV) infection is highly prevalent in some subpopulations with AIDS. HCV is linked to hepatocellular carcinoma (HCC) and possibly non-Hodgkin lymphoma (NHL), but the impact of AIDS on these associations is uncertain. We used U.S. registry data to study HCC and NHL risk in 304,411 adults with AIDS, comparing cohort subgroups with high prevalence (hemophiliacs and injection drug users) or low prevalence (homosexual men, heterosexuals, and others) of HCV infection. The ratio of observed to expected cancer cases (standardized incidence ratio [SIR]) measured risk relative to the general population. Sixty-one HCC cases were observed (SIR, 7.5; 95% confidence interval, 5.7-9.6). Risk for HCC was higher in subgroups with high prevalence of HCV infection than in subgroups with low prevalence of HCV infection (SIR: 11.4 versus 5.5, respectively; p =.004). Subjects developed the following NHL grades: low, 35 cases; intermediate, 1035 cases; high, 784 cases; and unspecified, 1395 cases. For each NHL grade, SIRs were highest in subgroups with low prevalence of HCV infection. These data suggest an effect of HCV infection on HCC risk among adults with AIDS. On the other hand, NHL risk was not higher for groups in whom HCV infection was prevalent.

Absence of simian virus 40 in human brain tumors from northern India

Simian virus 40 (SV40), a monkey polyomavirus, was a contaminant of early poliovirus vaccines administered to millions of individuals in the 1950s and early 1960s. SV40 causes brain tumors in laboratory animals, and SV40 DNA sequences have been variably identified in human choroid plexus tumors and ependymomas. We studied the possible association between SV40 and human brain tumors in northern India, where humans have frequent contact with SV40-infected rhesus macaques. DNA from pathologic specimens from 33 ependymomas, 14 choroid plexus tumors and 18 control brain tissues (contused brain, brain metastases) was extracted and analyzed under masked conditions. We used real-time PCR to detect and quantify SV40 (T antigen) and human (GAPDH) DNA sequences. The SV40 PCR assay detected as few as 10 copies of SV40 DNA and had a linear range from 1 x 10(2) to 1 x 10(6) copies. SV40 DNA was detected in 1 specimen (an ependymoma). However, few SV40 DNA copies were detected in this sample (<10 copies, equivalent to <1 copy/350 cells, based on simultaneous GAPDH quantification), and SV40 was not detected when this sample was retested. Our findings do not support a role for SV40 in choroid plexus tumors or ependymomas from northern India.

Kaposi's sarcoma-associated herpesvirus infection in elderly Jews and non-Jews from New York City

BACKGROUND

Worldwide, Kaposi's sarcoma (KS) occurs in immunocompetent elderly adults, especially men. Elderly Jews have relatively high KS risk, but it is unclear whether this indicates heightened prevalence of KS-associated herpesvirus (KSHV), the KS agent. We studied Jewish and non-Jewish patients at a New York City geriatrics clinic.

METHODS

We measured plasma antibodies against K8.1 (a KSHV glycoprotein) by enzyme immunoassay and against viral latency antigens by immunofluorescence assay. Individuals positive by either were considered KSHV-seropositive. Titres were performed for positive subjects. We used polymerase chain reaction to quantify circulating KSHV DNA.

RESULTS

Of 467 subjects (median age 80 years), 40 were KSHV-seropositive (8.6%). Seroprevalence was 8.8% among Jews (18 of 204), similar to other religious groups, and did not differ by sex or region of birth. However, K8.1 antibody titres were higher in men than women (geometric mean titre 177 versus 35, P = 0.03) and increased with age (P = 0.02). The K8.1 titres were higher in three people from Central/Eastern Europe (1,280, 1,280, 320), all of whom were Jewish, than in others (geometric mean titre 39, P = 0.006). The single person with detectable circulating KSHV (457 copies/million cells) had the highest titre (5,120).

CONCLUSIONS

The KSHV seroprevalence was not elevated among elderly Jews, despite their known high risk for KS. However, among KSHV-seropositive individuals, K8.1 titres were highest in subgroups at greatest risk for KS (men, older individuals, people from Central/Eastern Europe) and may identify individuals with poor immune control of KSHV replication during asymptomatic infection.

Pleural and peritoneal lymphoma among people with AIDS in the United States

OBJECTIVE

To describe the occurrence and characteristics of pleural and peritoneal lymphoma in a large cohort of persons with AIDS in 11 regions in the United States.

METHODS

We used AIDS and cancer registries to identify cases of non-Hodgkin lymphoma (NHL) among 304,439 adults with AIDS. NHLs were categorized by site codes into pleural/peritoneal lymphoma and other NHLs. Data on age, sex, HIV exposure category, histology, history of Kaposi sarcoma (KS), CD4 counts, and survival were analyzed.

RESULTS

Fourteen lymphomas were identified (four within the pleura, 10 in the peritoneum) representing 0.13% (95% confidence interval [CI], 0.05-0.20) of 10,510 cases of NHL. Those with pleural/peritoneal lymphoma were similar to those with other NHLs in age (median, 43 years), race (79% white, 7% black, 14% Hispanic), and HIV transmission category (86% homosexual men), but they tended to have a higher prevalence of prior KS (29% vs. 12%; p =.06). More cases of pleural/peritoneal lymphoma had immunoblastic histology than did other NHLs (43% vs. 22%; p =.06). CD4 counts for pleural/peritoneal lymphomas were also higher than for other NHLs (median 203 vs. 65 cells/mm3; p =.05), but post-NHL survival was similar (median 7.1 vs. 5.1 months, respectively; p =.32).

CONCLUSIONS

Pleural and peritoneal lymphomas are a rare subtype of AIDS-associated NHL, occurring with less severe immune deficiency than for other NHLs. The increased frequency among persons with prior KS suggests a common etiology, presumably infection with KS-associated herpesvirus, as found in primary effusion lymphoma.

Merkel cell carcinoma and HIV infection

Merkel cell carcinoma (MCC) is a rare skin cancer that occurs more frequently after organ transplantation or B-cell malignancy, conditions of suppressed or disordered immunity. To assess further whether immune suppression increases MCC risk, we studied its occurrence in a cohort of 309365 individuals with acquired immunodeficiency syndrome (AIDS) by using linked AIDS and cancer registries. We identified six cases of MCC, corresponding to a relative risk of 13.4 (95% CI 4.9-29.1) compared with the general population. These results suggest that immune suppression induced by the human immunodeficiency virus increases MCC risk.

Human immunodeficiency virus infection, aging, and cancer

HIV infection increases non-Hodgkin's lymphoma and Kaposi's sarcoma risk. Among HIV-uninfected persons, risk for these malignancies and others increases with age. As HIV-infected persons age, new patterns in cancer incidence may emerge. In this article, data from the AIDS-Cancer Registry Match study are presented on risk for Kaposi's sarcoma and lung cancer among persons with AIDS. For 132,346 homosexual men with AIDS, Kaposi's sarcoma incidence was highest for men 30-39 years old (5.0 cases/100 person-years) and declined with age (P(trend) <.0001). This trend likely arises from variation in Kaposi's sarcoma herpesvirus prevalence among homosexual men. For 239,257 adults with AIDS (all risk groups), lung cancer incidence increased with age, and was higher than in the general population (P <.0001), probably reflecting heavy smoking among HIV-infected adults. Identifying separate effects of HIV and aging on cancer risk will require detailed data on individuals' HIV infection status and exposures to known carcinogens.

Cancers associated with Kaposi's sarcoma (KS) in AIDS: a link between KS herpesvirus and immunoblastic lymphoma

Kaposi's sarcoma (KS), common among persons with acquired immunodeficiency syndrome (AIDS), is caused by KS herpesvirus (KSHV) but whether KSHV causes other malignancies is uncertain. Using linked United States AIDS and cancer registries, we measured the incidence of specific malignancies in persons with AIDS (4-27 months after AIDS onset). We identified associations with KSHV by calculating a relative risk: cancer incidence in persons with KS (all were KSHV-infected) divided by incidence in persons without KS. Using Poisson regression, relative risks were adjusted for human immunodeficiency virus risk group, gender, age, race, and calendar year. We included 189 159 subjects (26 972 with KS). Immunoblastic lymphoma was significantly associated with KS (506 cases; relative risks: unadjusted 2.44, 95%CI 2.00-2.96, adjusted 1.58, 95%CI 1.29-1.93). Only one immunoblastic lymphoma had pleura as primary site. None of 37 other specified malignancies (other non-Hodgkin lymphomas, haematological malignancies, solid tumours) was significantly associated with KS. In summary, the association of immunoblastic lymphoma with KS was specific among examined malignancies and remained significant after statistical adjustment. Our findings, and the previously demonstrated presence of KSHV in the histologically related primary effusion lymphoma, suggest that KSHV is involved in the pathogenesis of some immunoblastic lymphomas.

Thirty-five year mortality following receipt of SV40- contaminated polio vaccine during the neonatal period

Early poliovirus vaccines, both inactivated and live attenuated, were inadvertently contaminated with simian virus 40 (SV40), a monkey virus known to be oncogenic for newborn hamsters. Although large epidemiologic studies have not identified an elevated cancer risk in persons who received SV40-contaminated vaccines, fragments of SV40 DNA have recently been identified in certain human tumours. We report the follow-up of a cohort of 1073 persons, unique because they received SV40-contaminated poliovirus vaccines as newborns in 1961-63. A previous report of the status of these subjects as of 1977-79 identified 15 deaths, none due to cancer. The present study utilized the National Death Index to identify deaths in the cohort for the years 1979-96. Expected deaths were calculated from Cleveland area sex-, age-, race- and year-specific mortality rates. Increased mortality from all causes was not found. 4 deaths from cancer were found compared to 3.16 expected (P = 0.77). However, 2 deaths from testicular cancer occurred, compared to 0.05 expected (P = 0.002), which may be a chance finding due to multiple comparisons. There were 2 deaths due to leukaemia, a non-significant finding, and no deaths due to tumours of the types putatively associated with SV40. Although these results are, for the most part, consistent with other negative epidemiologic investigations of risks from SV40-contaminated vaccines, further study of testicular cancer may be warranted, and it will be important to continue monitoring this cohort which is now reaching middle-age.

Strategies for diagnosing and treating suspected acute bacterial sinusitis: a cost-effectiveness analysis

OBJECTIVE

Symptoms suggestive of acute bacterial sinusitis are common. Available diagnostic and treatment options generate substantial costs with uncertain benefits. We assessed the cost-effectiveness of alternative management strategies to identify the optimal approach.

DESIGN

For such patients, we created a Markov model to examine four strategies: 1) no antibiotic treatment; 2) empirical antibiotic treatment; 3) clinical criteria-guided treatment; and 4) radiography-guided treatment. The model simulated a 14-day course of illness, included sinusitis prevalence, antibiotic side effects, sinusitis complications, direct and indirect costs, and symptom severity. Strategies costing less than 50,000 dollars per quality-adjusted life year gained were considered "cost-effective."

MEASUREMENTS AND MAIN RESULTS

For mild or moderate disease, basing antibiotic treatment on clinical criteria was cost-effective in clinical settings where sinusitis prevalence is within the range of 15% to 93% or 3% to 63%, respectively. For severe disease, or to prevent sinusitis or antibiotic side effect symptoms, use of clinical criteria was cost-effective in settings with lower prevalence (below 51% or 44%, respectively); empirical antibiotics was cost-effective with higher prevalence. Sinus radiography-guided treatment was never cost-effective for initial treatment.

CONCLUSIONS

Use of a simple set of clinical criteria to guide treatment is a cost-effective strategy in most clinical settings. Empirical antibiotics are cost-effective in certain settings; however, their use results in many unnecessary prescriptions. If this resulted in increased antibiotic resistance, costs would substantially rise and efficacy would fall. Newer, expensive antibiotics are of limited value. Additional testing is not cost-effective. Further studies are needed to find an accurate,low-cost diagnostic test for acute bacterial sinusitis.

Trends in human immunodeficiency virus type 1 (HIV-1) load among HIV-1-infected children with hemophilia

In human immunodeficiency virus type 1 (HIV-1)-infected persons, virus load (serum/plasma level of HIV) predicts outcome. Virus load trends have been characterized in adults and infants but not in children. Virus load trends in 22 male children with hemophilia who acquired HIV-1 postnatally (age 0.7-5.2 years at seroconversion) were studied. The mean HIV-1 load 2 years after seroconversion was 4.40 log10 copies/mL, and the mean change over time (slope) was 0.03 log10 copies/(mL x year). Significant among-children variation was apparent: a random effects model predicted that 95% of children had early virus loads 3.75-5.04 log10 copies/mL and slopes -0.07 to 0.12 log10 copies/(mL x year). Higher early virus loads and higher slopes were each associated with increased mortality (P=.006 and P=.03, respectively). In conclusion, those subjects had virus load trends similar to those in adults. Early virus loads were lower than those in vertically infected infants, which suggests that factors changing soon after birth affect viral replication.

Cause-specific mortality associated with HIV and HTLV-II infections among injecting drug users in the USA

BACKGROUND

Human T-lymphotropic virus type II (HTLV-II) is widespread among injecting drug users (IDU) and may contribute to the risk of leukemia/lymphoma, neurodegenerative disease, and perhaps pneumonia, especially with HIV co-infection.

METHODS

In 1987--1991, 6570 IDU were tested for HIV and HTLV-II antibodies. In 1998, they were matched to the National Death Index. Numbers of observed deaths of each cause were compared by standardized mortality ratios with the numbers expected, using sex-, race-, age-, and year-specific rates in the general population. Relative risk (RR) associated with each virus, compared to uninfected drug users, was estimated by Poisson modeling.

RESULTS

There were 1351 deaths, including 683 (15%) of 4604 participants who enrolled seronegative for both viruses; 328 (47%) of 701 who had HIV but not HTLV-II infection; 220 (21%) of 1033 who had HTLV-II but not HIV infection; and 120 (52%) of 232 who were infected by both viruses. Compared to the general population, mortality for participants with neither virus was increased 4.3-fold [95% confidence interval (CI), 4.0--4.7] and was significantly elevated for virtually every cause of death. With HIV, mortality from medical causes, but not external causes, was increased 3.7-fold (95% CI, 3.3--4.2), particularly with AIDS and related conditions. With HTLV-II, all-cause mortality was reduced (RR, 0.8; 95% CI, 0.7--0.9), with no statistically significant reduction or elevation for any specific cause. A non-significant excess of tuberculosis deaths (RR, 4.6; 95% CI, 0.8--25.2) was noted with HTLV-II, but there was no excess mortality from leukemia/lymphoma, other malignancies, or neurodegenerative disease.

CONCLUSIONS

Without HIV or HTLV-II, IDU had profoundly increased mortality from medical and external causes. HIV was specifically associated with death due to AIDS and related conditions. HTLV-II infection was not significantly associated with mortality from any cause, suggesting that it is not a significant human pathogen, even when present with HIV infection.

Appendectomy and subsequent risk of inflammatory bowel diseases

BACKGROUND

Case-control studies have reported an inverse relationship between appendectomy and the risk of ulcerative colitis, but the association has not been confirmed in prospective studies.

METHODS

Using national hospital discharge registry data in Denmark, the authors followed up 154,434 patients who underwent appendectomy during the period 1977 to 1989 to investigate whether they had subsequent hospitalizations for ulcerative colitis and Crohn's disease. Ratios of observed-to-expected first hospitalizations for inflammatory bowel diseases served as measures of the relative risk (RR).

RESULTS

Hospitalization for ulcerative colitis occurred in 84 patients who had appendectomies versus 97.0 expected (RR = 0.87; 95% CI, 0.69-1.07). RRs were not significantly reduced in subgroups defined by sex, age, time since appendectomy, calendar period, or cause of appendectomy. Hospitalization for Crohn's disease occurred in excess (RR = 2.88; 95% CI, 2.45-3.39; n = 150), notably in the first year after appendectomy (RR = 10.83; 95% CI, 8.49-13.62; n = 73); but after 5 years, the RR was not significantly elevated.

CONCLUSIONS

This large population-based cohort study failed to support a significant inverse association between appendectomy and ulcerative colitis risk in the first decade after the operation. The excess of Crohn's disease shortly after appendectomy most likely reflects differential diagnostic problems in patients newly presenting with abdominal pain.

Association of cancer with AIDS-related immunosuppression in adults

CONTEXT

Large-scale studies are needed to determine if cancers other than Kaposi sarcoma, non-Hodgkin lymphoma, and cervical cancer occur in excess in persons with human immunodeficiency virus (HIV) infection or acquired immunodeficiency syndrome (AIDS).

OBJECTIVES

To examine the general cancer pattern among adults with HIV/AIDS and to distinguish immunosuppression-associated cancers from other cancers that may occur in excess among persons with HIV/AIDS.

DESIGN, SETTING, AND SUBJECTS

Analysis of linked population-based AIDS and cancer registry data from 11 geographically diverse areas in the United States, including 302 834 adults aged 15 to 69 years with HIV/AIDS. The period of study varied by registry between 1978 and 1996.

MAIN OUTCOME MEASURE

Relative risks (RRs) of cancers, calculated by dividing the number of observed cancer cases by the number expected based on contemporaneous population-based incidence rates. We defined cancers potentially influenced by immunosuppression by 3 criteria: (1) elevated overall RR in the period from 60 months before to 27 months after AIDS; (2) elevated RR in the 4- to 27-month post-AIDS period; and (3) increasing trend in RR from before to after AIDS onset.

RESULTS

Expected excesses were observed for the AIDS-defining cancers, but non-AIDS-defining cancers also occurred in statistically significant excess (n = 4422; overall RR, 2.7; 95% confidence interval [CI], 2.7-2.8). Of individual cancers, only Hodgkin disease (n = 612; RR, 11.5; 95% CI, 10.6-12.5), particularly of the mixed cellularity (n = 217; RR, 18.3; 95% CI, 15.9-20.9) and lymphocytic depletion (n = 36; RR, 35.3; 95% CI, 24.7-48.8) subtypes; lung cancer (n = 808; RR, 4.5; 95% CI, 4.2-4.8); penile cancer (n = 14; RR, 3.9; 95% CI, 2.1-6.5); soft tissue malignancies (n = 78; RR, 3.3; 95% CI, 2.6-4.1); lip cancer (n = 20; RR, 3.1; 95% CI, 1.9-4.8); and testicular seminoma (n = 115; RR, 2.0; 95% CI, 1.7-2.4) met all 3 criteria for potential association with immunosuppression.

CONCLUSION

Although occurring in overall excess, most non-AIDS-defining cancers do not appear to be influenced by the advancing immunosuppression associated with HIV disease progression. Some cancers that met our criteria for potential association with immunosuppression may have occurred in excess in persons with HIV/AIDS because of heavy smoking (lung cancer), frequent exposure to human papillomavirus (penile cancer), or inaccurately recorded cases of Kaposi sarcoma (soft tissue malignancies) in these persons. However, Hodgkin disease, notably of the mixed cellularity and lymphocytic depletion subtypes, and possibly lip cancer and testicular seminoma may be genuinely influenced by immunosuppression.

Risk of T-cell lymphomas in persons with AIDS

Lymphomas in persons with AIDS are mostly B-cell types, but T-cell lymphomas have also been reported. We examined T-cell lymphoma risk in the 2-year period after AIDS onset by linking 302,834 adults with AIDS to cancer registry data. Of 6,788 cases of non-Hodgkin's lymphoma (NHL) with specified histologies, 96 (1.4%) were T-cell lymphomas. Assessment was based on clinical diagnosis and histology because T-cell marker data were inadequate, but when present, marker data supported the T-cell diagnosis. The relative risk of T-cell lymphoma, estimated by standardized incidence ratio, was 15.0 (95% confidence interval: 10.0--21.7). Risks were increased for all subtypes, including mycosis fungoides, peripheral lymphomas, cutaneous lymphomas, and adult T-cell leukemia/lymphoma (ATLL). HIV-related immunodeficiency could be important, but differences between the population developing AIDS and the general population (e. g., immigration from the Caribbean region for ATLL) might independently increase T-cell lymphoma risk.

Patellar versus hamstring tendons in anterior cruciate ligament reconstruction: A meta-analysis

PURPOSE: To compare the outcome of ACL reconstuction using patellar tendon (PAT) to that when using hamstring tendons. Type of Study: Meta-analysis of controlled trials of patellar tendon versus hamstring tendons for ACL reconstruction. METHODS: Meta-analysis is a systematic method for statistical analyses that allows compilation of combined data from various independent studies. This allows one to assess the potential benefits of various treatments when conclusions based on individual studies are difficult to assess. We conducted a meta-analyses (M-A) using controlled trials (CTs) to determine if there are differences between the 2 methods. Although both surgical techniques have potential for good results, we hypothesized that there are differences in outcomes between these techniques. We included CTs that used standard evaluation techniques with a minimum 2-year follow-up. Outcomes evaluated included: return to preinjury level of activity, KT testing, Lachman scores, pivot shift scores, range of motion (ROM) loss in flexion and extension, complications, and failures. Relative risks for each outcome were calculated for each study and pooled across studies using a fixed effects method. RESULTS: Four studies fulfilled our inclusion criteria. Relative risks with 95% confidence intervals and P values were obtained for each of the outcomes listed above. The results show significant differences between PAT and semitendinosus and gracilis tendon (ST&G) reconstructions. PAT patients have a greater chance of attaining a statically stable knee (as measured by KT) and nearly a 20% greater chance of returning to preinjury activity levels. CONCLUSIONS: Although both techniques, as performed in the late 1980s and early 1990s, yielded good results, PAT reconstuction led to higher postoperative activity levels and greater static stability than hamstring reconstruction. This is statistically significant based on this meta-analysis.

Latent class analysis of human herpesvirus 8 assay performance and infection prevalence in sub-saharan Africa and Malta

Human herpesvirus 8 (HHV-8) is thought to be highly prevalent in Mediterranean countries and sub-Saharan Africa, where it causes Kaposi's sarcoma in a small proportion of infected immunocompetent persons. However, the lack of serological tests with established accuracy has hindered our understanding of the prevalence, risk factors and natural history of HHV-8 infection. We tested 837 subjects from Congo, Botswana (mostly young adults) and Malta (elderly adults), using an immunofluorescence assay and 2 enzyme immunoassays (EIAs, to viral proteins K8.1 and orf65). Each assay found HHV-8 seroprevalence to be high (49-87%) in the African populations and generally lower (9-54%) in Malta. However, there was only modest agreement among tests regarding which subjects were seropositive (3-way kappa, 0.05-0.34). We used latent class analysis to model this lack of agreement, estimating each test's sensitivity and specificity and each population's HHV-8 prevalence. Using this approach, the K8.1 EIA had consistently high sensitivity (91-100%) and specificity (92-100%) across populations, suggesting that it might be useful for epidemiological studies. Compared with the K8.1 EIA, both the immunofluorescence assay and the orf65 EIA had more variable sensitivity (80-100% and 58-87%, respectively) and more variable specificity (57-100% and 48-85%, respectively). HHV-8 prevalence was 7% among elderly Maltese adults. Prevalence was much higher (82%) in Congo, consistent with very high Kaposi's sarcoma incidence there. Prevalence was also high in Botswana (87% in Sans, an indigenous group, and 76% in Bantus), though Kaposi's sarcoma is not common, suggesting that additional co-factors besides HHV-8 are needed for development of Kaposi's sarcoma.

Meta-analysis of diagnostic tests for acute sinusitis

To facilitate management of acute sinusitis, we conducted a meta-analysis of published studies comparing diagnostic tests for this disorder. Thirteen studies were identified through literature search. Based on sinus puncture/aspiration (considered most accurate), 49-83% of symptomatic patients had acute sinusitis. Compared with puncture/aspiration, radiography offered moderate ability to diagnose sinusitis (summary receiver operator curve [SROC] area, 0.83). Using sinus opacity or fluid as the criterion for sinusitis, radiography had sensitivity of 0.73 and specificity of 0.80. Studies evaluating ultrasonography revealed substantial variation in test performance. The clinical evaluation, particularly risk scores formally incorporating history and physical examination findings, had moderate ability to identify patients with positive radiographs (SROC area, 0.74). Many studies were of poor quality, with inadequately described test methods and unblinded test interpretation. In conclusion, acute sinusitis is common among symptomatic patients. Radiography and clinical evaluation (especially risk scores) appear to provide useful information for diagnosis of sinusitis.

Heterogeneity and statistical significance in meta-analysis: an empirical study of 125 meta-analyses

For meta-analysis, substantial uncertainty remains about the most appropriate statistical methods for combining the results of separate trials. An important issue for meta-analysis is how to incorporate heterogeneity, defined as variation among the results of individual trials beyond that expected from chance, into summary estimates of treatment effect. Another consideration is which 'metric' to use to measure treatment effect; for trials with binary outcomes, there are several possible metrics, including the odds ratio (a relative measure) and risk difference (an absolute measure). To examine empirically how assessment of treatment effect and heterogeneity may differ when different methods are utilized, we studied 125 meta-analyses representative of those performed by clinical investigators. There was no meta-analysis in which the summary risk difference and odds ratio were discrepant to the extent that one indicated significant benefit while the other indicated significant harm. Further, for most meta-analyses, summary odds ratios and risk differences agreed in statistical significance, leading to similar conclusions about whether treatments affected outcome. Heterogeneity was common regardless of whether treatment effects were measured by odds ratios or risk differences. However, risk differences usually displayed more heterogeneity than odds ratios. Random effects estimates, which incorporate heterogeneity, tended to be less precisely estimated than fixed effects estimates. We present two exceptions to these observations, which derive from the weights assigned to individual trial estimates. We discuss the implications of these findings for selection of a metric for meta-analysis and incorporation of heterogeneity into summary estimates. Published in 2000 by John Wiley & Sons, Ltd.

Identifying human herpesvirus 8 infection: performance characteristics of serologic assays

Epidemiologic studies of infection with the oncogenic human herpesvirus 8 (HHV-8) depend on serologic methods to diagnose infection. However, optimal strategies for identifying HHV-8 infection remain undefined. We therefore evaluated four enzyme-linked immunoassays (EIAs) and one immunofluorescence assay (IFA) using sera from 87 individuals with the prototype HHV-8 disease, Kaposi's sarcoma (KS), and 210 participants in a hemophilia study (who were presumed not to be infected with HHV-8). Assays performed reasonably well in distinguishing between infected and uninfected persons, with receiver operator curve areas between 0.86 and 0.96. Nonetheless, IFA had only 86% sensitivity and 88% specificity, and no EIA simultaneously had sensitivity and specificity above 90% for any of the optical density (OD) cutpoints used to define seropositivity. Some assays were markedly less sensitive with diluted KS sera, suggesting that they poorly identify low-titer antibodies present in asymptomatic infection. We also developed a classification tree that categorized individuals as seropositive if they had OD > 2.00 on recombinant K8.1 protein EIA or if they had both K8.1 OD between 0.51 and 2.00 and positive IFA results; this strategy had between 80% and 90% sensitivity and 95% and 100% specificity. Overall, assays performed adequately for use in most epidemiologic investigations, but wider applications will require improved tests.

Vaccines for preventing typhoid fever

BACKGROUND

Whole cell vaccines, consisting of relatively crude preparations of Salmonella typhi administered parenterally, are effective but have a high incidence of adverse effects. Two vaccines have been developed more recently. Ty21a (an attenuated strain of S. typhi administered orally) and Vi (the purified bacterial capsule, given parenterally), have appeared less toxic than the older whole cell vaccines and are thought to be equally effective.

OBJECTIVES

The objective of this review was to assess the effects of typhoid fever vaccines.

SEARCH STRATEGY

We searched the Cochrane Library, Medline, Index Medicus, Embase and reference lists of articles.

SELECTION CRITERIA

Randomised trials comparing typhoid vaccines to other types of vaccine or placebo.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed trial quality and extracted data.

MAIN RESULTS

Seventeen studies, involving nearly two million people, were included. For the whole cell vaccines single dose regimens provided significant protection for the first two years. Two dose regimens provided significant protection for five years. For the Ty21a vaccine, both two and three dose regimens provided statistically significant protection for two years. The three dose regimen provided protection in the third and fourth years, but protection was not statistically significant in the fifth year. The Vi vaccine provided protection for two years, but the protection in the third year was not significant. The three year cumulative efficacy of two doses of whole cell vaccines was 73% (95% confidence interval 65-80), three doses of Ty21a was 51%, (95% confidence interval 35 to 63) and one dose of Vi was 55% (95% confidence interval 30 to 71). Data on adverse effects were limited, but indicate that whole cell vaccines are more toxic than the newer Ty21a and Vi vaccines.

REVIEWER'S CONCLUSIONS

The whole cell vaccines provided more prolonged protection than either the Ty21a vaccine or the Vi vaccine. However whole cell vaccines are associated with higher toxicity.