Occupational exposure to human immunodeficiency virus and hepatitis B virus: a comparative analysis of risk

A nationwide cross-sectional survey on hepatitis B and C screening among workers in Japan

In Japan, there is no publicly funded screening for hepatitis B virus (HBV) and hepatitis C virus (HCV) infections (using HBs antigen and HCV antibody, respectively) among workers, and workplace health programmes play a crucial role in reducing viral hepatitis-related deaths. The national number of hepatitis screening tests conducted in the workplace is unknown. To provide baseline data for policy formulation, we conducted a nationwide survey to estimate these parameters using data from approximately 10.5 million workers (6.8 million men and 3.8 million women) who underwent mandatory health examinations in their workplaces between April 2016 and March 2017. Among these workers, 494,303 (5.23%, 95% confidence interval [CI] 5.22%-5.24%) and 313, 193 (3.82%, 95% CI 3.81%-3.84%) were screened for HBV and HCV, respectively. Among those who were screened, 0.28% (95% CI 0.27-0.30%) and 0.35% (95% CI 0.33-0.37%) tested positive for HBs antigen and HCV antibody, respectively. According to the age-specific prevalence from the survey an estimated 0.30 and 0.14 million workers in Japan require treatment for HBV and HCV, respectively. To reduce viral hepatitis-related deaths by efficiently identifying workers who need treatment and promoting access to treatment, one-time hepatitis screening of all workers should be considered.

Knowledge, attitude, and practice of Iranian surgeons about blood-borne diseases

BACKGROUND

Perhaps more than any other healthcare worker, it is the surgeons who are at an increased risk of exposure to hepatitis B (HB) virus, hepatitis C virus, and human immunodeficiency virus. The aim of this study was to evaluate surgeons' concerns regarding risk awareness and behavioral methods of protection against blood-borne pathogen transmission during surgery.

MATERIALS AND METHODS

A 31-item questionnaire with a reliability coefficient of 0.73 was used. Of 575 surgeons invited to participate from three universities and one national annual surgical society between May and July 2007, 430 (75%) returned completed forms.

RESULTS

Concern about being infected with blood-borne diseases was more than 70 (from a total score of 100). Only 12.9% of surgeons always used double gloves. Complete vaccination against HB was done in about 76% of surgeons and only 56.8% had checked their HB surface antibody (anti-HBs) level. Older surgeons never used double gloves (P = 0.001).

CONCLUSION

Iranian surgeons are not aware of the correct percentage of infected patients with and seroconversion rate of blood-borne diseases, do not use double gloves adequately, do not report their needlestick injuries, vaccinate against HB, and check anti-HBs after vaccination. Educational meetings, pamphlets, and facilities must be provided to health care workers, informing them of hazards, prevention, and postexposure prophylaxis to needlestick injuries, vaccination efficacy, and wearing double gloves.

Risk of transmission of hepatitis B virus through childhood immunization in northwestern China

Transmission of bloodborne pathogens by means of unsafe injection practices is a significant public health problem in developing countries. Although the overall proportion for immunization is low among injections, unsafe immunization practices affect mostly infants, a population with an increased likelihood of becoming hepatitis B virus carriers. This study estimated the prevalence of unsafe injection among vaccinators working at the peripheral level in northwestern China and the risk of HBV infections among infant vaccinees, and analyzed factors contributing to the most prevalent unsafe practice: the reuse of a non-sterilized reusable syringe among infants. A knowledge-attitude-practice survey was conducted in which 180 peripheral vaccinators selected by multi-stage cluster sampling in each of four provinces and one autonomous region completed a self-administered questionnaire. The lack of observational data for assessing the validity of the self-reported practices made the study prone to systematic respondent bias that may have skewed the results towards underestimation of unsafe practices. The minimum estimate of the percentage of peripheral vaccinators reusing a syringe and/or needle without sterilization between infants was 7.2-55.0%, whereas the percentage of those disposing of used disposable syringes and needles inappropriately was 8.9-23.3% by province. According to a model-based estimate, the annual number of HBV infections among 100,000 fully immunized children due to unsafe immunization injection was at least 135-3120. An insufficient supply of syringes and the attitude to justify reuse were significantly associated with the unsafe reuse of a reusable syringe in most part of the area studied. Introduction of auto-disable syringes may contribute to curb the unsafe practices, but the development of safe collection and disposal procedures for used syringes and needles is prerequisite. Sufficient supply of equipment as well as training, supervision, and monitoring targeting specifically on the risk behaviors and concerned attitudes are essential for behavior changes among the vaccinators.

Cost-effectiveness of transfusion of platelet components prepared with pathogen inactivation treatment in the United States

Background: The Intercept Blood System (IBS) for platelets has been developed to reduce pathogen transmission risks during transfusions.

Objective: This study was a comprehensive economic analysis of the cost-effectiveness of using the IBS for single-donor apheresis platelets (AP) and random-donor pooled platelet concentrates (PC) versus AP and PC without the IBS in the United States in patient populations in which platelets are commonly transfused.

Methods: All data used in this analysis were summarized from existing published sources (primarily indexed in MEDLINE) and data on file at Baxter Healthcare Corporation (Chicago, Illinois) and Cerus Corporation (Concord, California). A literature-based decision-analytic model was developed to assess the economic costs and clinical outcomes associated with the use of AP and PC treated with the IBS for several conditions and procedures that account for a considerable proportion of the platelet usage in the United States: acute lymphocytic leukemia, non-Hodgkin's lymphoma, coronary artery bypass graft, and hip arthroplasty Risks of infection with HIV, hepatitis C virus (HCV), hepatitis B virus, human T-cell lymphotropic virus type 1, or bacterial agents were incorporated into the model. Possible benefits of reduction of the risk of emerging HCV like pathogens and elimination of the need for gamma irradiation were explored in sensitivity analyses.

Results: The incremental cost per quality-adjusted life-year gained by using AP + IBS versus untreated AP ranged from $1,308,833 to $4,451,650 (without bacterial testing) and $4,759,401 to $22,968,066 (with bacterial testing). Corresponding figures for PC + IBS versus untreated PC ranged from $457,586 to $1,816,060. Inclusion of emerging HCV like virus and the elimination of the need for gamma irradiation improved the cost-effectiveness to a range of $177,695 to $1,058,127 for AP without bacterial testing, $176,572 to $1,330,703 for AP with bacterial testing, and $22,888 to $153,564 for PC. The model was most likely to be affected by mortality from bacterial contamination, IBS effect on platelet utilization, and the inclusion of potential benefits (ie, gamma irradiation and/or emergent HCVlike virus). The model was relatively insensitive to changes in the IBS price and viral transmission risks.

Conclusions: The cost-effectiveness of pathogen inactivation via the IBS for platelets is comparable to that of other accepted blood safety interventions (eg, nucleic acid amplification technology). The IBS for platelets may be considered a desirable strategy to increase the safety of platelet transfusions and a potential insurance against the threat of emerging pathogens.

Needlestick injuries among medical students

BACKGROUND

Concern about occupational exposure to bloodborne pathogens exists, and medical students, who lack in experience in patient care and surgical technique, may be at an increased exposure risk.

METHODS

This prospective cohort study evaluated needlestick injuries and practices regarding the use of protective strategies against bloodborne pathogens in medical students. A questionnaire was developed and sent to 224 medical students.

RESULTS

Of 224 students, 146 students (64%) returned questionnaires. Forty-three students (30%) reported needlestick injuries that most commonly occurred in the operating room; 86% of students reported always using double gloves in the operating room; 90% reported always wearing eye protection, and all but one student had been vaccinated against hepatitis B. A concern about contracting a bloodborne pathogen through work was noted in 125 students, although they usually reported that this concern only slightly influenced their decision regarding a career subspecialty.

CONCLUSION

Medical students have a high risk for needlestick injuries, and attention should be directed to protection strategies against bloodborne pathogens.

Seroprevalences of hepatitis B and C among health care workers in Turkey

We determined the seroprevalence of hepatitis B virus (HBV) and hepatitis C virus (HCV) among health care workers (HCWs) at Gülhane Military Medical Academy, Haydarpasa Training Hospital in Istanbul, Turkey. Between April 1998 and September 2000, 702 HCWs were included in the study. The blood samples were tested for hepatitis B surface antigen (HBsAg), hepatitis B surface antibody (anti-HBs) and HCV antibody (anti-HCV) using third-generation tests, with confirmation by reverse transcriptase-polymerase chain reaction. Seroprevalence rates were compared with those detected in 5670 blood donors during the same period. HBsAg, anti-HBs and anti-HCV were detected in 21 (3.0%), in 480 (68.4%) and in 2 (0.3%) of 702 HCWs respectively. HBsAg and anti-HCV rates were 2.1 and 0.4% in blood donors, respectively. These data show that the prevalence rates of HBV and HCV were similar with prevalence rates detected in randomized blood donors showing that universal infection-control precautions and encouraging HBV vaccination reduces HCW infection with hepatotropic viruses.

A review of the application of health economics to health and safety in healthcare

A literature review is described which aimed to evaluate economic evaluations of health and safety interventions in healthcare. Severe limitations in the methodological rigor of nearly all the published work were identified. Most effort had been invested in costing studies, which are not economic evaluations in their own right. Problems were identified with valuing benefits in health and safety because they frequently take many years to emerge and are difficult to measure. Understanding of economic techniques within the health and safety professions was limited, resulting in wide-ranging assumptions being made as to the positive economic impact of health and safety interventions. Reasons for this are explored and include the subjective benefits of intervention programmes being so impressive and the likelihood of economic savings so great that there have been few demands for objective data. Healthcare managers, health economists, and health and safety professionals have not traditionally worked together and have inherent misunderstandings of each other roles. The review concludes that the aim of future research should be to assist the National Health Service (NHS) to make valid decisions about health and safety investment and risk control methods. This should be done with the aim of improving the health of those affected by or working within the healthcare sector.

AIDS policy modeling for the 21st century: an overview of key issues

Decisions about HIV prevention and treatment programs are based on factors such as program costs and health benefits, social and ethical issues, and political considerations. AIDS policy models--that is, models that evaluate the monetary and non-monetary consequences of decisions about HIV/AIDS interventions--can play a role in helping policy makers make better decisions. This paper provides an overview of the key issues related to developing useful AIDS policy models. We highlight issues of importance for researchers in the field of AIDS policy modeling as well as for policy makers. These include geographic area, setting, target groups, interventions, affordability and effectiveness of interventions, type and time horizon of policy model, and type of economic analysis. This paper is not intended to be an exhaustive review of the AIDS policy modeling literature, although many papers from the literature are discussed as examples; rather, we aim to convey the composition, achievements, and challenges of AIDS policy modeling.

Surgeon-patient barrier efficiency monitored with an electronic device in three surgical settings

Blood-borne viral pathogens are an occupational threat to health care workers (HCWs), particularly those in the operating room. A major risk is posed by accidental penetrating injury, but skin contamination with body fluids from an infected patient, with prolonged intimate cutaneous contact, is a frequent occurrence during surgery, carrying further risk of transdermal infection. We have monitored barrier failure in three surgical settings (microsurgery, orthopedic surgery, general surgery) by means of an electronic surveillance device. A total of 111 surgical procedures were monitored: 67 microsurgeries, 22 orthopedic surgeries, and 22 general surgeries. Of the 278 electronic alarms signaling barrier failure, 44 (15.8%) were associated with glove perforation, 39 of which (88.6%) were not perceived by the operator. In 16 of those, the skin was visibly stained with the patient's blood. Altogether, 76 of the alarms (27.3%) were consequent to contacts caused by soaked gowns/sleeves, and 121 (43.5%) were attributed to hydration of latex porosities; 37 alarms (13.4%) were unexplained false positives. On only one occasion did a surgeon observe blood stains on his hands without a previous alarm; this event was classified as a device failure due to incorrect wiring. Double-gloving offered satisfactory protection against skin contamination during microsurgery but not during orthopedic surgery. The data presented here indicate that electronic monitoring of the surgical barrier enables prompt detection of barrier failure, especially at the level of the gloves, thereby limiting skin contamination with patients' body fluids during surgery.

Risk of infection from needle reuse at a phlebotomy center

OBJECTIVES

This study determined infection risk for HIV, hepatitis B virus (HBV), and hepatitis C virus (HCV) from needle reuse at a phlebotomy center that possibly exposed 3810 patients to infection.

METHODS

We used a model for the risk of infection per blood draw, supplemented by subsequent testing results from 1699 patients.

RESULTS

The highest risk of transmission was for HBV infection: 1.1 x 10(-6) in the best case and 1.2 x 10(-3) in the (unlikely) worst case. Subsequent testing yielded prevalence rates of 0.12%, 0.41%, and 0.88% for HIV, HBV, and HCV, respectively, lower than National Health and Nutrition Examination Survey III prevalence estimates.

CONCLUSIONS

The infection risk was very low; few, if any, transmissions are likely to have occurred.

Contagious diseases in competitive sport: what are the risks?

Great concern is often expressed over the possibility of contagion among athletes in competitive sports, particularly sports with much person-to-person contact. Human immunodeficiency virus (HIV) is only the most notorious of infectious agents; potentially, other viruses, bacteria, and even fungi may be involved. Because of the concern, however, special attention is paid to HIV and hepatitis B infections. For most of the infections considered, the athlete is more at risk during activities off the playing field than while competing. Inclusion of immunizations against measles and hepatitis B among prematriculation immunization requirements (PIRs) for colleges and universities would eliminate these two diseases from the list of dangers to college athletes and all students. Education, rather than regulations, should remain the cornerstone in considering the risks to athletes from contagious diseases.

Exposure to human immunodeficiency virus among healthcare workers in South Africa

There have been no reports in the literature on occupational hazards of HIV in developing countries. The aim of this study was to evaluate occupational exposure to HIV in healthcare workers in Durban, South Africa. Individuals with occupational exposure to HIV were interviewed. Thirteen percent of the staff reported injuries with HIV positive patients. Registrars in training were the highest risk group (60%). Of the injuries, 94% were percutaneous and 65% occurred during emergency surgery. The commonest place of injury was the operating theater (46%) and the commonest procedure associated with accidental exposure was cesarean section (57%). Fifty-one percent were not wearing eye protection during procedures and although 83% initiated post-exposure prophylaxis (PEP), 48% discontinued treatment due to side effects of the drugs. Occupational exposure to HIV is common in the developing world. Rectifiable factors identified in this study that contributes to the milieu of occupational acquisition of HIV include less than proper adherence to universal precaution; inadequate documentation procedures and failure of a large percentage of respondents to complete post-exposure prophylaxis.

Economic methods for measuring the quality of life associated with HIV infection

BACKGROUND

Quality of life is measured as utilities for cost-effectiveness analyses.

OBJECTIVE

To test the adequacy of three common utility elicitation methods for individuals with Human Immunodeficiency Virus (HIV) disease.

MEASUREMENTS

HIV-positive participants (n = 75) rated three standardized health states (symptomatic HIV infection, minor AIDS defining illness, and major AIDS defining illness) with two utility elicitation methods (Standard Gamble [SG], and Time Trade-off [TTO]) and one value method (Visual Analog [VA]). Participants also rated their own health with one utility method (Health Utilities Index [HUI]) and one conventional quality of life method (Medical Outcomes Study--HIV Health Survey [MOS-HIV]).

RESULTS

For all states, SG and TTO scores ranged from near 0.00 (equivalent to death) to 1.00 (best possible quality of life). Mean scores for symptomatic HIV were similar with the SG (0.80) and TTO (0.81) but higher than with the VA (0.70). Similar results were observed for minor AIDS defining illnesses (0.65, 0.65, 0.46 respectively) and major AIDS defining illnesses (0.42, 0.44, 0.25 respectively). Discrepant SG and TTO scores were observed in many individuals and were not explained by demographic characteristics. As expected, HUI scores of an individual's own health were related to the disease state. Four of ten MOS-HIV subscales (overall health, physical functioning, role functioning, and pain) were also related to disease state. HUI scores were correlated with the MOS-HIV score for overall health and for all MOS-HIV subscales except health transition.

CONCLUSIONS

Mean utility scores for HIV-related health states elicited by the Standard Gamble and Time Trade-off were similar but a large degree of individual variation persists. Economic methods provide imprecise estimates of the quality of life associated with HIV infection.

Surgeons' concern and practices of protection against bloodborne pathogens

OBJECTIVE

To evaluate surgeons' concern regarding risk awareness and behavioral methods of protection against bloodborne pathogen transmission during surgery.

METHODS

A 29-item questionnaire was sent to 914 surgeons from two universities and two surgical societies.

RESULTS

The questionnaire was returned by 768 active surgeons. Slight or moderate concern about contracting human immunodeficiency virus (HIV) was reported by most surgeons; 8% reported extreme concern and 4% reported no concern. In total, 605 surgeons reported having been vaccinated against hepatitis B; surgeons in practice <7 years were most likely to be vaccinated. Most surgeons did not routinely use double gloves: 92 of 768 surgeons reported that they always use double gloves when performing surgery, and 83 reported that they usually use double gloves. There was a statistically significantly higher proportion of surgeons who always or usually use double gloves who also had hepatitis B vaccinations. Most surgeons incorrectly estimated the seroconversion rates with exposure to a patient with HIV (66% incorrect), hepatitis B (88% incorrect), or hepatitis C (84% incorrect). Most surgeons never or rarely report needle-stick injuries, and only 17% always report needle-stick injuries.

CONCLUSIONS

Most surgeons underestimate the risk of bloodborne pathogens and do not routinely use double gloves.

Risk of blood contamination of health care workers in spine surgery. A study of 324 cases

STUDY DESIGN

The relative risk of blood contamination during spine surgery was studied using data collected from 324 procedures.

OBJECTIVES

To analyze demographic factors that predict blood-borne pathogens in the population of spine surgery patients, study the rates and patterns of blood contamination in health care workers (i.e., skin-penetrating incidents and nonpenetrating surface skin contamination from patients' blood) and compare those risks with those in other surgical departments, and analyze the effectiveness of barrier systems worn by the surgical team.

SUMMARY OF BACKGROUND DATA

The Centers for Disease Control and Prevention has reported 49 health care workers infected by the human immunodeficiency virus through occupational exposure. Several studies have noted the risk of blood contamination in various surgical departments, but the relative risk during spine surgery has not been determined.

METHODS

This year-long survey included 9795 cases, or 60,789 health care worker--patient contacts, of which spine disorders comprised 324 cases (2234 health care workers and patients). Data collection forms were designed and inservice training conducted with operating room staffs. Information regarding type of case, staff position (surgeon, assistant, scrub nurse, circulator), protective clothing worn, length of operating room time, blood loss, incidence of blood spills, was recorded, among other data.

RESULTS

Prevalence of human immunodeficiency virus in patients in the overall series was 0.19% versus 0.93% in spine patients. The rate of HCW contamination in the overall series was 7.76%, of which 0.92% resulted from skin-penetrating incidents. Contamination in spine surgery occurred in 31.86% of cases, of which 1.23% were the result of skin-penetrating incidents.

CONCLUSIONS

Health care workers in spine surgery have a statistically significant overall higher risk of blood contamination than do those in other surgical departments. The increased risk occurred with blood contacting intact skin. There was no higher risk for skin penetrating injury. Analysis of data suggests that health care workers always should wear double gloves, forearm-reinforced gowns, and eye protection.

Physicians' assessments of the utility of health states associated with human immunodeficiency virus (HIV) and hepatitis B virus (HBV) infection

An understanding of quality of life (QOL) with human immunodeficiency virus (HIV) is important because the merits of prevention and treatment alternatives may depend substantially on how these interventions affect QOL. Physicians' views about QOL are important, because they influence the therapeutic options that physicians consider or offer, the recommendations that physicians make, and because they are important for the analysis of certain policy questions. We assessed physicians' utilities of health states associated with HIV infection, and hepatitis B virus (HBV) infection; assessment of utilities for HBV was induced to provide a comparison with HIV utilities. We surveyed 200 housestaff and staff physicians in an academic medical centre by anonymous paper-based questionnaire and used the time-tradeoff method to assess physicians' utilities of the health states. On a scale in which 0 was equivalent to death, and 1 was equivalent to good health, the median utilities for asymptomatic HIV infection, symptomatic HIV infection, and AIDS were 0.833, 0.417, and 0.167, respectively (p < 0.01 or each two-way comparison). Median utilities for asymptomatic HBV infection, mildly symptomatic HBV infection, and severely symptomatic HBV infection were 0.917, 0.667, and 0.167, respectively (p < 0.01 for each two-way comparison). Although physicians varied substantially in the ratings of health states, they assessed the utility of life with HIV disease, including asymptomatic infection, as severely reduced. Studies of the effectiveness and cost-effectiveness of preventive and therapeutic interventions for HIV should evaluate the effect of the intervention on utility-based assessments of QOL. Studies that do not assess such effects may significantly underestimate or overestimate the value of these interventions, depending on the intervention's effect on QOL.

Seroconversion to HBV associated with seroconversion to HIV in a cohort of intravenous drug misusers in Turin, Italy

Between March 1986 and March 1994, the seroconversion to HBV associated to the seroconversion to HIV was investigated in 120 HIV seroconverters drawn from 2368 i.v. drug misusers screened for HIV, HBV and STDs. Among the 185 individuals susceptible to HIV and HBV at intake (41/120 HIV seroconverters and 144/364 HIV-negative controls), HBV seroconversion was associated with the seroconversion to HIV (p = 0.006) and history of more than 3 sexual partners per year (p = 0.000). Only the history of more than 3 partners per year remained associated with the HBV seroconversion in the conditional regression. The associated seroconversion to HIV and HBV was linked to the short period of i.v. drug injections (p = 0.032), history of more than 3 partners per year (p = 0.000) and more than 3 i.v. drug injections per day (p = 0.016). Compared to the seroconverters to HBV alone, the seroconverters to HBV and HIV were likely to have higher frequency of i.v. drug injection per day on univariate (p = 0.031) and multivariate analysis (p = 0.024). The seroconverters to both the viruses differed from the seroconverters to HIV alone in the year of drug debut (p = 0.045), short period of i.v. drug use (p = 0.048) and high frequency of injection per day (p = 0.008). The multivariate analysis confirmed only the association with high frequency of injection per day (p = 0.033). Higher risk of HIV seroconversion from the debut of i.v. drug use was observed in the subjects with concurrent HBV seroconversion (Log-Rank test: p = 0.0008).

A nurse's right to refuse a patient care assignment

Ethics is a set of moral principles or values--a guiding philosophy for behavior. Ethical dilemmas in the health care setting occur daily. Perioperative nurse managers need to consider basic ethical principles when resolving these dilemmas, and they must keep in mind that solutions need to serve the best interests of all people involved in given situations. This article discusses criteria by which a nurse can refuse a patient care assignment and those by which a nurse manager can require that a nurse perform a patient care assignment.

The decision to enter a randomized trial of tamoxifen for the prevention of breast cancer in healthy women: an analysis of the tradeoffs

OBJECTIVE

Interest in breast cancer prevention has led to the Breast Cancer Prevention Trial (BCPT), a controversial randomized trial of tamoxifen for women at risk for breast cancer. The goal of our study was to determine whether the potential benefits of enrolling in the randomized trial of prophylactic tamoxifen outweigh the potential risks.

METHODS

We used a decision analytic model based on the available data on tamoxifen treatment benefits in women with breast cancer and extrapolated to its use in healthy women.

RESULTS

For a 50-year-old woman with a breast cancer risk twice that of the average woman her age, the BCPT offers an increase in life expectancy of about 9 days, a gain that is modest compared with other health interventions. For women ages 35 to 60 who meet the minimum risk of breast cancer for trial eligibility, the trial increases life expectancy by about 8 or 9 days. Assumptions about the effect of tamoxifen on the incidence of endometrial and liver cancer and on quality of life associated with tamoxifen did not alter our findings.

CONCLUSIONS

Advocates and opponents of the BCPT should temper their concerns to reflect the modest absolute benefits and harms associated with the trial. Although women at increased risk for breast cancer should be aware of the likely overall benefit associated with entry into the trial, for most women, entry into the BCPT is unlikely to alter substantially their length of life, in either a beneficial or harmful manner.

Development of outcome-based practice guidelines: a method for structuring problems and synthesizing evidence

BACKGROUND

The growth in guidance development projects has focused attention on the methods used in developing the guideline. For a guideline to be sound it should be linked on the basis of scientific evidence to the very health outcome that the guideline is designed to promote.

METHODS

Structuring a health intervention as an influence diagram, a decision model (1) allows for the identification of the relevant benefits, harms, and costs that may result from an intervention; (2) provides an explicit link between the intervention and these outcomes, a crucial prerequisite for the development of an outcome-based guideline; and (3) identifies the evidence that must be synthesized to predict the effect of the intervention on the health outcomes.

EXAMPLE

In the development of a guideline related to prevention of opportunistic infections in HIV-infected persons, we would define the interventions (for example, use of medication for PCP pneumonia), the intended health outcome (a potential reduction in the number of opportunistic infections), and the evidence that demonstrates that the intervention produces the desired outcome. If PCP prophylaxis is delayed, the HIV-infected person is exposed to a undue risk of PCP, with its attendant morbidity and mortality. If it is initiated too early, the person incurs excess monetary costs and may experience additional side-effect-associated morbidity.

EXAMPLE

The intervention in question is screening for HIV infection, and the outcomes of interest are the medical benefits and harms associated with screening and the financial costs (and savings) that a screening program would incur. Screening for HIV infection differs from many clinical questions because it has potential benefit both to the persons screened and to public health if the screened person reduces risk behaviors that might transmit HIV infection.

CONCLUSIONS

Structuring a problem with an influence diagram: delineates an explicit link between interventions and outcomes; focuses the questions to be addressed (a series of more sharply defined questions, each of which we may be able to answer based on direct evidence, replaces a much broader question [should we screen for HIV?], which cannot be answered directly); and highlights the importance of a clear, unambiguous statement whose benefit and costs are under consideration.