Predictors of positivity for hepatitis B and the derivation of a selective screening rule in a Canadian sexually transmitted disease clinic

Developing a predictive model to prioritize human immunodeficiency virus partner notification in North Carolina

BACKGROUND

Disease intervention specialists (DIS) in North Carolina have less time to conduct partner notification because of competing responsibilities while simultaneously facing increased case loads because of increased human immunodeficiency virus (HIV) testing. We developed a model to predict undiagnosed HIV infection in sexual partners to prioritize DIS interviews.

METHODS

We abstracted demographic, behavioral, and partnership data from DIS records of HIV-infected persons reported in 2 North Carolina surveillance regions between January 1, 2003 and December 31, 2007. Multiple logistic regression with generalized estimating equations was used to develop a predictive model and risk scores among newly diagnosed persons and their partners. Sensitivities and specificities of the risk scores at different cutoffs were used to examine algorithm performance.

RESULTS

Five factors predicted a partnership between a person with newly diagnosed HIV infection and an undiagnosed partner--a period of 4 weeks or fewer between HIV diagnosis and DIS interview, no history of crack use, no anonymous sex, fewer total sexual partners reported to DIS, and sexual partnerships between an older index case and younger partner. Using this model, DIS could choose an appropriate cutoff for locating a particular partner by determining the weight of false negatives relative to false positives.

CONCLUSIONS

Although the overall predictive power of the model is low, it is possible to reduce the number of partners that needs to be located and interviewed while maintaining high sensitivity. If DIS continue to pursue all partners, the model would be useful in identifying partners in whom to invest more resources for locating.

An economic assessment of pre-vaccination screening for hepatitis A and B

OBJECTIVE

The availability of a single vaccine active against hepatitis A and B may facilitate prevention of both infections, but complicates the question of whether to conduct pre-vaccination screening. The authors examined the cost-effectiveness of pre-vaccination screening for several populations: first-year college students, military recruits, travelers to hepatitis A-endemic areas, patients at sexually transmitted disease clinics, and prison inmates.

METHODS

Three prevention protocols were examined: (1) screen and defer vaccination until serology results are known; (2) screen and begin vaccination immediately to avoid a missed vaccination opportunity; and (3) vaccinate without screening. Data describing pre-vaccination immunity, vaccine effectiveness, and prevention costs borne by the health system (i.e., serology, vaccine acquisition, and administration) were derived from published literature and U.S. government websites. Using spreadsheet models, the authors calculated the ratio of prevention costs to the number of vaccine protections conferred.

RESULTS

The vaccinate without screening protocol was most cost-effective in nine of 10 analyses conducted under baseline assumptions, and in 69 of 80 sensitivity analyses. In each population considered, vaccinate without screening was less costly than and at least equally as effective as screen and begin vaccination. The screen and defer vaccination protocol would reduce costs in seven populations, but effectiveness would also be lower.

CONCLUSIONS

Unless directed at vaccination candidates with the highest probability of immunity, pre-vaccination screening for hepatitis A and B immunity is not cost-effective. Balancing cost reduction with reduced effectiveness, screen and defer may be preferred for older travelers and prison inmates.

An economic assessment of pre-vaccination screening for hepatitis A and B

OBJECTIVE

The availability of a single vaccine active against hepatitis A and B may facilitate prevention of both infections, but complicates the question of whether to conduct pre-vaccination screening. The authors examined the cost-effectiveness of pre-vaccination screening for several populations: first-year college students, military recruits, travelers to hepatitis A-endemic areas, patients at sexually transmitted disease clinics, and prison inmates.

METHODS

Three prevention protocols were examined: (1) screen and defer vaccination until serology results are known; (2) screen and begin vaccination immediately to avoid a missed vaccination opportunity; and (3) vaccinate without screening. Data describing pre-vaccination immunity, vaccine effectiveness, and prevention costs borne by the health system (i.e., serology, vaccine acquisition, and administration) were derived from published literature and U.S. government websites. Using spreadsheet models, the authors calculated the ratio of prevention costs to the number of vaccine protections conferred.

RESULTS

The vaccinate without screening protocol was most cost-effective in nine of 10 analyses conducted under baseline assumptions, and in 69 of 80 sensitivity analyses. In each population considered, vaccinate without screening was less costly than and at least equally as effective as screen and begin vaccination. The screen and defer vaccination protocol would reduce costs in seven populations, but effectiveness would also be lower.

CONCLUSIONS

Unless directed at vaccination candidates with the highest probability of immunity, pre-vaccination screening for hepatitis A and B immunity is not cost-effective. Balancing cost reduction with reduced effectiveness, screen and defer may be preferred for older travelers and prison inmates.

HIV and hepatitis B surveillance in First Nations alcohol and drug treatment centres in British Columbia, Canada, 1992-2000

We provide ongoing HIV and Hepatitis B surveillance in residential First Nations alcohol and drug treatment centres in British Columbia, Canada. All clients entering the centres are offered confidential viral testing as part of an education program on sexually transmitted diseases. Participation is voluntary and approximately two thirds of clients choose to be tested. Information about risk factors for communicable disease and immunization status is not recorded. The testing program began in January 1992. As of September 2000, 2,345 people have been tested for HIV. Nine tested positive, giving a prevalence of 3.8 per 1,000 (95% confidence interval: 1.3 to 6.3 per 1,000), lower than among all British Columbians who choose to be tested (8.5 per 1,000). Also, 2,166 people were tested for hepatitis B surface antibody, 23% of these were positive, 10% were positive for hepatitis B core antibody (indicating prior infection with hepatitis B). Seven clients (3.2 per 1,000; 95% Cl: 0.8 to 5.6 per 1,000) were positive for hepatitis B surface antigen and are therefore presumed to be chronically infected. The prevalence of hepatitis B markers was intermediate between what has previously been found in high risk groups and that found in the general population.

Chronic hepatitis B infection in Canada

Recent developments in the treatment and prevention of hepatitis B virus (HBV) infections warrant revisiting important epidemiological questions, such as how prevalent is chronic HBV infection in Canada, in which Canadian subpopulations are HBV prevalence rates the highest, in what percentage of infected individuals is the virus actively replicating, and how many infected Canadians are candidates for antiviral therapy? Currently available data suggest the overall prevalence of HBV-infected individuals in the general population is approximately 2%, with 5% to 10% having serological evidence of previous HBV infection. In high risk groups, such as street-connected individuals, Aboriginals and immigrants from endemic areas, these rates of viral prevalence and serological evidence of previous HBV infection are approximately two to 10 and five to 10 times higher, respectively, than in the general population. Candidates for antiviral therapy range from less than 1% of infected Aboriginals to 15% to 30% of Asians with chronic HBV. From these data, it is clear that chronic HBV remains an important public health problem in this country. Hence, resources must be identified to enhance Canadians' awareness of HBV infection, maintain, if not expand, efforts to identify and implement safe and effective antiviral therapy for HBV-infected individuals, and continue programs for universal vaccination to prevent new HBV infections.

Epidemiology of hepatitis B in Canada

OBJECTIVE

To provide a current and comprehensive review of the epidemiology of hepatitis B virus (HBV) in Canada.

DATA SOURCES

Published and unpublished epidemiological studies and surveillance reports of the past decade, primarily from Canada were studied. Fifty reports addressing HBV surveillance, incidence and prevalence, transmission-associated risk factors, co-infections, and prevention strategies were reviewed.

DATA SYNTHESIS

HBV infection is an important vaccine-preventable infectious disease in Canada. The incidence rate of clinically recognized, acute HBV infection in 1998/1999 was estimated to be 2.3/100,000 people or approximately 700 cases a year. The prevalence of HBV carriers is estimated to be 0.5% to 1.0% of the population, but varies substantially according to population-specific risk factors. Most acute HBV infections are associated with injection drug use or high risk heterosexual activities, but 20% to 30% of acute cases did not report any identified risk factors. Surveillance activities such as the National Notifiable Disease Reporting system provide information regarding trends and risk factors. The primary preventive strategy for HBV consists of universal immunization for preadolescents and/or infants. Other strategies, such as the universal prenatal screening and postnatal immunization, and the prevention of nosocomial acquisition, are also important. The recently described hepatitis B surface antigen (HBsAg) escape mutants may not be detected by current HBsAg test assays, and the existing HBV vaccines may not protect vaccinees from infections by such mutants.

CONCLUSION

Ongoing surveillance and research are required to assess risk factors for HBV transmission, evaluate the effectiveness of immunization programs and monitor the impact of HBsAg escape mutants.