Does gabapentin provide benefit for patients with knee OA? A benefit-harm and cost-effectiveness analysis

OBJECTIVE

Gabapentin can treat neuropathic pain syndromes and has increasingly been prescribed to treat nociplastic pain. Some patients with knee osteoarthritis (OA) suffer from both nociceptive and nociplastic pain. We examined the cost-effectiveness of adding gabapentin to knee OA care.

METHOD

We used the Osteoarthritis Policy Model, a validated Monte Carlo simulation of knee OA, to examine the value of gabapentin in treating knee OA by comparing three strategies: 1) usual care, gabapentin sparing (UC-GS); 2) targeted gabapentin (TG), which provides gabapentin plus usual care for those who screen positive for nociplastic pain on the modified PainDETECT questionnaire (mPD-Q) and usual care only for those who screen negative; and 3) universal gabapentin plus usual care (UG). Outcomes included cumulative quality-adjusted life years (QALYs), lifetime direct medical costs, and incremental cost-effectiveness ratios (ICERs), discounted at 3% annually. We derived model inputs from published literature and national databases and varied key input parameters in sensitivity analyses.

RESULTS

UC-GS dominated both gabapentin-containing strategies, as it led to lower costs and more QALYs. TG resulted in a cost increase of $689 and a cumulative QALY reduction of 0.012 QALYs. UG resulted in a further $1,868 cost increase and 0.036 QALY decrease. The results were robust to plausible changes in input parameters. The lowest TG strategy ICER of $53,000/QALY was reported when mPD-Q specificity was increased to 100% and AE rate was reduced to 0%.

CONCLUSION

Incorporating gabapentin into care for patients with knee OA does not appear to offer good value.

Cost-effectiveness of health coaching and financial incentives to promote physical activity after total knee replacement

OBJECTIVE

We evaluated the cost-effectiveness of Telephonic Health Coaching and Financial Incentives (THC + FI) to promote physical activity in total knee replacement recipients.

DESIGN

We used the Osteoarthritis Policy Model, a computer simulation of knee osteoarthritis, to evaluate the cost-effectiveness of THC + FI compared to usual care. We derived transition probabilities, utilities, and costs from trial data. We conducted lifetime analyses from the healthcare perspective and discounted all cost-effectiveness outcomes by 3% annually. The primary outcome was the Incremental Cost-Effectiveness Ratio (ICER), defined as the ratio of the differences in costs and Quality-Adjusted Life Years (QALYs) between strategies. We considered ICERs <$100,000/QALY to be cost-effective. We conducted one-way sensitivity analyses that varied parameters across their 95% confidence intervals (CI) and limited the efficacy of THC + FI to 1 year or to 9 months. We also conducted a probabilistic sensitivity analysis (PSA), simultaneously varying cost, utilities, and transition probabilities.

RESULTS

THC + FI had an ICER of $57,200/QALY in the base case and an ICER below $100,000/QALY in most deterministic sensitivity analyses. THC + FI cost-effectiveness depended on assumptions about long-term efficacy; when efficacy was limited to 1 year or to 9 months, the ICER was $93,300/QALY or $121,800/QALY, respectively. In the PSA, THC + FI had an ICER below $100,000/QALY in 70% of iterations.

CONCLUSIONS

Based on currently available information, THC + FI might be a cost-effective alternative to usual care. However, the uncertainty surrounding this choice is considerable, and further research to reduce this uncertainty may be economically justified.

Model-based evaluation of cost-effectiveness of nerve growth factor inhibitors in knee osteoarthritis: impact of drug cost, toxicity, and means of administration

OBJECTIVE

Studies suggest nerve growth factor inhibitors (NGFi) relieve pain but may accelerate disease progression in some patients with osteoarthritis (OA). We sought cost and toxicity thresholds that would make NGFi a cost-effective treatment for moderate-to-severe knee OA.

DESIGN

We used the Osteoarthritis Policy (OAPol) model to estimate the cost-effectiveness of NGFi compared to standard of care (SOC) in OA, using Tanezumab as an example. Efficacy and rates of accelerated OA progression were based on published studies. We varied the price/dose from $200 to $1000. We considered self-administered subcutaneous (SC) injections (no administration cost) vs provider-administered intravenous (IV) infusion ($69-$433/dose). Strategies were defined as cost-effective if their incremental cost-effectiveness ratio (ICER) was less than $100,000/quality-adjusted life year (QALY). In sensitivity analyses we varied efficacy, toxicity, and costs.

RESULTS

SOC in patients with high levels of pain led to an average discounted quality-adjusted life expectancy of 11.15 QALYs, a lifetime risk of total knee replacement surgery (TKR) of 74%, and cumulative discounted direct medical costs of $148,700. Adding Tanezumab increased QALYs to 11.42, reduced primary TKR utilization to 63%, and increased costs to between $155,400 and $199,500. In the base-case analysis, Tanezumab at $600/dose was cost-effective when delivered outside of a hospital. At $1000/dose, Tanezumab was not cost-effective in all but the most optimistic scenario. Only at rates of accelerated OA progression of 10% or more (10-fold higher than reported values) did Tanezumab decrease QALYs and fail to represent a viable option.

CONCLUSIONS

At $100,000/QALY, Tanezumab would be cost effective if priced ≤$400/dose in all settings except IV hospital delivery.

Surveillance for isocyanate asthma: a model based cost effectiveness analysis

AIMS

Because logistical and financial obstacles impede using large prospective cohort studies, surveillance decisions in occupational settings must often be made without evidence of relative benefits and costs. Using the example of isocyanate induced asthma, the most commonly reported immune mediated occupational asthma, the authors developed a model based approach to evaluate the costs and benefits of surveillance from both an employer and a societal perspective.

METHODS

The authors used a mathematical simulation model of isocyanate asthma to compare annual surveillance to passive case finding. Outcome measures included symptom free days (SFD), quality adjusted life years (QALY), direct costs, productivity losses, and incremental cost effectiveness ratio (CER), measured from the employer and the societal perspectives. Input data were obtained from a variety of published sources.

RESULTS

For 100,000 exposed workers, surveillance resulted in 683 fewer cases of disability over 10 years. Surveillance conferred benefits at an incremental cost of 24,000 dollars/QALY (employer perspective; 13.33 dollars/SFD) and was cost saving from the societal perspective. Results were sensitive to assumptions about sensitisation rate, removal rates, and time to diagnosis, but not to assumptions about therapy costs and disability rates.

CONCLUSIONS

Baseline results placed the CER for surveillance for isocyanate asthma within the acceptable range. Costs from the societal and employer perspective differed substantially with a more attractive CER from the societal perspective, suggesting opportunities for employer/societal cost sharing. The analysis demonstrates the value of a model based approach to evaluate the cost effectiveness of surveillance programmes for isocyanate asthma, and to inform shared decision making among clinicians, patients, employers, and society. Such a modeling approach may be applicable to surveillance programmes for other work related conditions.

Prevention of human immunodeficiency virus-related opportunistic infections in France: a cost-effectiveness analysis

A simulation model of human immunodeficiency virus (HIV) disease, which incorporated French data on the progression of HIV disease in the absence of antiretroviral therapy and on cost, was used to determine the clinical impact and cost-effectiveness of different strategies for the prevention of opportunistic infections in French patients who receive highly active antiretroviral therapy (HAART). Compared with use of no prophylaxis, use of trimethoprim-sulfamethoxazole (TMP-SMZ) increased per-person lifetime costs from euro 185,600 to euro 187,900 and quality-adjusted life expectancy from 112.2 to 113.7 months, for an incremental cost-effectiveness ratio of euro 18,700 per quality-adjusted life-year (euro/QALY) gained. Compared with use of TMP-SMZ alone, use of TMP-SMZ plus azithromycin cost euro 23,900/QALY gained; adding fluconazole cost an additional euro 54,500/QALY gained. All strategies that included oral ganciclovir had cost-effectiveness ratios that exceeded euro 100,000/QALY gained. In the era of HAART, on the basis of French data, prophylaxis against Pneumocystis carinii pneumonia, toxoplasmic encephalitis, and Mycobacterium avium complex bacteremia is cost-effective. Prophylaxis against fungal and cytomegalovirus infections is less cost-effective than are other therapeutic options for HIV disease and should remain of lower priority.

Use of health services by insurance status among children with asthma

OBJECTIVES

It is well known that asthmatic children receiving Medicaid use the emergency department (ED) more frequently than otherwise-insured asthmatic children. However, the extent to which this difference is attributable to provider characteristics, medication use, access to primary care, and symptomatology is poorly understood. These factors were explored as independent predictors of health care utilization.

METHODS

Baseline data from a prospective cohort study of childhood asthma severity were used. Subjects were recruited from seven New England hospitals. Home interviews collected data on monthly symptoms, health care visits, insurance status, as well as sociodemographics and asthma-related risk factors (n = 804). Characteristics of providers' practices, board certifications, and asthma specialty were obtained from Folio's Medical Dictionaries for Connecticut and Massachusetts.

RESULTS

After adjusting for frequency of asthma-related primary care visits, primary provider practice type, use of asthma specialist, age, gender, medication use, and symptomatology, Medicaid children still used the ED more frequently for asthma services than privately insured children (RR, 1.7; 95% CI, 1.1, 2.5). In general, race/ethnicity did not modify the relationship between insurance status and health care use, except that black children receiving Medicaid were 90% (95% CI, 0.0, 0.7) less likely to have had > or = 3 routine primary care visits for asthma in the previous year than black privately insured children. White children receiving Medicaid were 2.5 (95% CI, 1.0, 6.9) times more likely to use the ED for asthma than privately insured white children.

CONCLUSIONS

The results suggest that enabling, structural, and need factors do not necessarily explain observed differences in pediatric asthma health care use by insurance status. Future investigation must explore other explanatory factors such as maternal attitudes and beliefs and patient-provider communication.

Incidence of primary opportunistic infections in two human immunodeficiency virus-infected French clinical cohorts

BACKGROUND

Clinical guidelines for the prevention of opportunistic infections in human immunodeficiency virus (HIV)-infected individuals have been developed on the basis of natural history data collected in the USA. The objective of this study was to estimate the incidence of primary opportunistic infections in HIV-infected individuals in geographically distinct cohorts in France.

METHODS

We conducted our study on 2664 HIV-infected patients from the Tourcoing AIDS Reference Centre and the hospital-based information system of the Groupe d'Epidémiologie Clinique du SIDA en Aquitaine enrolled from January 1987 to September 1995 and followed through December 1995. We estimated: (1) CD4-adjusted incidence rates of seven primary opportunistic infections in the absence of prophylaxis for that specific infection or any antiretroviral drugs other than zidovudine; and (2) CD4 lymphocyte count decline.

RESULTS

The highest incidence rates for all opportunistic infections studied occurred in patients with CD4 counts < 200/microl. With CD4 counts < 50/microl, the most common opportunistic infections were toxoplasmic encephalitis (12.6 per 100 person-years) and Pneumocystis carinii pneumonia (11.4 per 100 person-years). Mycobacterium tuberculosis was the least common opportunistic infection (< 5.0/100 person-years). Even with CD4 counts > 300/microl, cases of Pneumocystis carinii pneumonia and toxoplasmic encephalitis were reported. The mean CD4 lymphocyte decline per month was 4.6 cells/microl. There was a significant association between HIV risk behaviour and the incidence of cytomegalovirus infection, between calendar year and the incidence of Pneumocystis carinii pneumonia, toxoplasmic encephalitis and Candida esophagitis, and between geographical area and the incidence of Pneumocystis carinii pneumonia and cytomegalovirus infection.

CONCLUSIONS

Geographical differences exist in the incidence of HIV-related opportunistic infections. These results can be used to define local priorities for prophylaxis of opportunistic infections.

Cost-effectiveness of inhaled corticosteroids in adults with mild-to-moderate asthma: results from the asthma policy model

BACKGROUND

Inhaled corticosteroids remain underused among United States-based clinicians in treating mild-to-moderate adult asthma.

OBJECTIVE

The purpose of this investigation was to estimate the clinical impact, health-related quality of life, cost, and cost-effectiveness of inhaled corticosteroid therapy in a population of patients aged 18 years and over with FEV(1) = 60% to 100% of predicted normal.

METHODS

We performed a cost-effectiveness analysis of quick relievers (eg, short-acting beta-agonists) on an as-needed basis plus inhaled corticosteroid therapy versus quick relievers alone. A mathematical simulation model was developed to forecast symptoms, acute exacerbations, quality-adjusted life-years (QALYs), health care costs, and cost-effectiveness, measured in both dollars per QALY gained and dollars per symptom-free day gained. All evaluation outcomes were discounted at an annual rate of 3% and measured over a 10-year planning horizon. Data on the natural history of disease, drug efficacy, patient preferences, and economic costs were obtained from a variety of observational cohorts, randomized trials, and patient surveys.

RESULTS

Over a 10-year period, use of inhaled corticosteroids increases total health costs from roughly $5,200 to $8,400 and improves QALYs from 6.8 to 7.0, implying an incremental cost of $13,500 per QALY gained. Costs per symptom-free day gained are $7.50. Both per-person acute exacerbations and hospitalizations are reduced by 33%. The cost-effectiveness findings are sensitive to the assumed efficacy and side-effects of inhaled corticosteroid therapy.

CONCLUSIONS

Inhaled corticosteroids appear to deliver good comparative value in adults with mild-to-moderate asthma. Although more research is needed to understand their impact on preferences regarding side effects and compliance, these findings might be useful for priority-setting in limited resource situations.

The cost effectiveness of combination antiretroviral therapy for HIV disease

BACKGROUND

Combination antiretroviral therapy with a combination of three or more drugs has become the standard of care for patients with human immunodeficiency virus (HIV) infection in the United States. We estimated the clinical benefits and cost effectiveness of three-drug antiretroviral regimens.

METHODS

We developed a mathematical simulation model of HIV disease, using the CD4 cell count and HIV RNA level as predictors of the progression of disease. Outcome measures included life expectancy, life expectancy adjusted for the quality of life, lifetime direct medical costs, and cost effectiveness in dollars per quality-adjusted year of life gained. Clinical data were derived from major clinical trials, including the AIDS Clinical Trials Group 320 Study. Data on costs were based on the national AIDS Cost and Services Utilization Survey, with drug costs obtained from the Red Book.

RESULTS

For patients similar to those in the AIDS Clinical Trials Group 320 Study (mean CD4 cell count, 87 per cubic millimeter), life expectancy adjusted for the quality of life increased from 1.53 to 2.91 years, and per-person lifetime costs increased from $45,460 to $77,300 with three-drug therapy as compared with no therapy. The incremental cost per quality-adjusted year of life gained, as compared with no therapy, was $23,000. On the basis of additional data from other major studies, the cost-effectiveness ratio for three-drug therapy ranged from $13,000 to $23,000 per quality-adjusted year of life gained. The initial CD4 cell count and drug costs were the most important determinants of costs, clinical benefits, and cost effectiveness.

CONCLUSIONS

Treatment of HIV infection with a combination of three antiretroviral drugs is a cost-effective use of resources.

Preevaluation of clinical trial data: the case of preemptive cytomegalovirus therapy in patients with human immunodeficiency virus

We developed a mathematical simulation model to anticipate outcomes from an upcoming trial of targeted, preemptive cytomegalovirus (CMV) therapy in high-risk, human immunodeficiency virus (HIV)-infected patients identified by means of CMV polymerase chain reaction screening. We estimated the costs and consequences of CMV prophylaxis in patients with CD4(+) counts < or =100 cells/microL under various assumptions regarding disease progression, complication rates, drug effects, and costs. Without CMV preemptive therapy, lifetime costs average $44,600 with expected duration of survival of 19.16 quality-adjusted life-months and 213 CMV cases per 1000 patients. Targeted preemptive therapy with orally administered valganciclovir increases costs and duration of survival to $46,900 and 19.63 quality-adjusted life-months, respectively. CMV cases decrease to 174 per 1000 patients. The cost per quality-adjusted life-year gained is $59,000. This result compares favorably with other strategies in end-stage HIV disease but hinges on valganciclovir cost and efficacy assumptions and the absence of minimally effective salvage antiretroviral therapy for HIV. The upcoming trial should resolve the clinical uncertainty surrounding some of these assumptions.

FEV(1) is associated with risk of asthma attacks in a pediatric population

BACKGROUND

FEV(1) is endorsed by the National Asthma Education and Prevention Program as a means for grading asthma severity. However, few data exist on the relationship between FEV(1) and asthma outcomes during long-term follow-up.

OBJECTIVE

We explored the relationship between the percent predicted FEV(1) (FEV(1)%) and subsequent asthma attacks in a longitudinal study of pediatric lung health.

METHODS

A retrospective cohort of 13,842 children (100,292 observations) seen annually over a 15-year interval was analyzed for measurement of pulmonary function, and a respiratory questionnaire was completed. Up to grade 9, a standard questionnaire was completed by a parent or guardian; thereafter it was completed by the patient. For each observation, the report of an attack during the past year was paired with FEV(1) recorded at the field survey 1 year earlier.

RESULTS

A progressive decrease in the proportion of individuals reporting an attack was associated with increasing decile of FEV(1)%. Two categorization schemes for FEV(1)% were examined: a scheme based on the National Asthma Education and Prevention Program recommendations (<60%, 60%-80%, and >80%), and an alternative scheme (<80%, 80%-100%, and >100%). In multivariate models, FEV(1)% was an independent predictor of attacks: among the parental report group, the odds ratios were 2.1 (95% CI, 1.3-3.4) and 1.4 (95% CI, 1.2-1.6) for FEV(1)% < 60% and FEV(1)% of 60% to 80% compared with FEV(1)% > 80%, respectively; and among the self-report group, odds ratios were 5.3 (95% CI, 2.2-12.9) and 1.4 (95% CI, 1.2-1.7) for FEV(1)% < 60% and FEV(1)% of 60% to 80% compared with FEV(1)% > 80%, respectively. With the alternative classification scheme, the relationship was similar, but the difference in risk between categories of FEV(1)% decreased.

CONCLUSION

The strong association between FEV(1)% and risk of asthma attack over the subsequent year supports an emphasis on objective measures of lung function in assessment of risk for adverse asthma outcomes.

Remarks on the role of economic modeling

BACKGROUND

Despite the growing scholarly acceptance of quantitative evaluation methods, modelers still struggle to define an appropriate role for their work at the decision-making level.

GOAL

To make observations about the policy relevance of mathematical and economic policy modeling in HIV and sexually transmitted disease prevention and treatment.

RESULTS

The debate is framed within the context of the inevitability of decision making. Viewed in this light, models can inform choices between competing alternatives by leveraging existing information, integrating data from multiple sources, addressing "what if" questions, evaluating future scenarios, and providing a uniform metric for evaluation.

CONCLUSIONS

The goal of model-based evaluation should not be to supplant the decision maker, but rather to redefine the terms of the debate using quantitative methods that make the beliefs and values that lie at the heart of all difficult choices explicit.

The cost-effectiveness of prophylaxis for Mycobacterium avium complex in AIDS

OBJECTIVE

To develop a simulation model to project costs, life expectancy, and cost-effectiveness in discounted dollars per quality-adjusted life-year (QALY) saved for clinical strategies to prevent Mycobacterium avium complex (MAC) in patients with AIDS.

METHODS

We used natural history data from the Multicenter AIDS Cohort Study, efficacy and toxicity data from randomized clinical trials, and cost data from the AIDS Cost and Services Utilization Survey. The model permits timing of prophylaxis to be stratified by CD4 count (201-300, 101-200, 51-100, and < or = 50/mm3), and allows combinations of prophylaxis, crossover to second- and third-line agents for toxicity, and consideration of adherence, resistance, and quality of life.

RESULTS

The model projects that the average HIV-infected patient with a beginning CD4 count between 201 and 300/mm3 has total lifetime costs of approximately $43,150 and a quality-adjusted life expectancy of 42.35 months. If azithromycin prophylaxis for M. avium complex is begun after the CD4 declines to 50/mm3, costs and quality-adjusted survival increase to approximately $44,040 and 42.78 months, respectively, for an incremental cost-effectiveness ratio of $25,000/QALY compared with no M. avium complex prophylaxis. Other prophylaxis options (i.e., rifabutin, clarithromycin, and combination therapies) either cost more but offer shorter survival, or have cost-effectiveness ratios above $260,000/QALY. Sensitivity analysis reveals that, for reasonable assumptions about quality of life, risk of infection, prophylaxis cost, adherence, and resistance, azithromycin remains the most cost-effective prophylaxis option.

CONCLUSIONS

Azithromycin prophylaxis, begun after the CD4 count has declined to 50/mm3, is the most cost-effective M. avium complex prophylaxis strategy. Consistent with new United States Public Health Service guidelines, it should be the first-line prophylaxis option.

Five minutes with the Governor

This paper aims to initiate a dialog among readers regarding the positioning and promotion of health-related decision analysis in the public sector. It is motivated by the author's personal observations that quantitative and economic evaluation methods continue to be viewed with skepticism by some public officials and that no consensus exists within our community as to what an appropriate message to such decision makers might be. A personal view of some key themes to be stressed in defining a vision for the field is presented.

Evaluation of therapeutic strategies: a new method for balancing risk and benefit

OBJECTIVE

A patient-specific drug safety-efficacy index was developed that combined objective clinical trial information about dose-related efficacy and toxicity with subjective perspectives on efficacy-toxicity trades.

METHODS

Patient preferences were systematically assessed using the probability tradeoff technique (PTT). Toxicity ranges over which a drug's efficacy exceeded the patient's minimally acceptable efficacy represented ranges of "surplus efficacy." These can be related to the dose interval in which a drug delivers this surplus efficacy. Seventy surplus efficacy functions (for 7 hypothetical drugs and 10 hypothetical preference curves) were simulated.

RESULTS

The analysis showed that index values change markedly by dose and patient preference, suggesting that different patients will benefit from different drugs depending on the dose prescribed and each patient's subjective assessment of the efficacy/toxicity tradeoff. In most situations, drugs achieve positive surplus efficacy only over limited dose ranges. The model was sensitive to different preference curves and discriminated well among drugs with different efficacy or safety profiles.

CONCLUSION

This index provides a new, systematic approach to choosing a specific therapeutic intervention and dosage, when known risks and benefits are reconciled against patient-specific preferences among an array of therapeutic alternatives.

Cost effectiveness of prophylaxis for opportunistic infections in AIDS. An overview and methodological discussion

Dramatic progress has recently been made in defining the pathogenesis and treatment of HIV infection. For the first time in the history of the AIDS epidemic, clinicians have at their disposal an understanding of the replication kinetics of HIV, reliable assays to measure viral load, an increasing number of effective agents to suppress viral replication and to reverse the process of immune system destruction, and a range of options for the treatment and prophylaxis of most of the major opportunistic infections in HIV disease. These remarkable advances are not without their costs, however. New antiretroviral therapies and opportunistic infection prophylaxis regimens impose considerable financial strain on public and private budgets for HIV patient care. They force decision-makers to confront a variety of competing considerations, including issues of length and quality of life, the risks of adverse effects and toxicities, and the dangers of promoting resistance. Questions regarding the continued appropriateness and efficiency of opportunistic infection prevention have prompted increased interest in studies of the cost effectiveness of HIV patient care. In this article, we reviewed the literature on the economic evaluation of prophylaxis for HIV-related complications. Section 1 provides background on recent scientific and clinical advances. Section 2 reviews the state-of-the-art understanding of the cost effectiveness of prophylaxis against specific opportunistic infections. Section 3 broadens the discussion to consider the more general question of optimal allocation of prophylaxis resources across competing opportunistic infections. In Section 4, we briefly examined the influence of cost-effectiveness evaluations on the development and refinement of clinical guidelines for HIV-related opportunistic infection prevention in the US. Section 5 presents some of the methodological challenges that arise in applying the methods of cost-effectiveness analysis to the particular case of opportunistic infection prevention in AIDS. We close, in Section 6, with a comment on directions for further research.

Acute scrotal symptoms in boys with an indeterminate clinical presentation: comparison of color Doppler sonography and scintigraphy

PURPOSE

To compare the performance of color Doppler ultrasonography (US) and scintigraphy in assessing testicular perfusion in boys with clinically equivocal presentations.

MATERIALS AND METHODS

Forty-one boys with clinically equivocal testicular perfusion underwent color Doppler US and scintigraphy. Studies were retrospectively classified as consistent with torsion, consistent with nontorsion, or indeterminate. Sensitivity and specificity were determined with alternate positivity criteria (indeterminate studies first considered positive and then negative for torsion).

RESULTS

Color Doppler US demonstrated nine of 11 cases of torsion and 23 of 30 cases of nontorsion, with one false-positive and eight indeterminate studies. Scintigraphy demonstrated 10 of 11 cases of torsion and 29 of 30 cases of nontorsion, with two indeterminate studies (both in patients with inguinal testis). When indeterminate studies were considered positive for torsion, specificity was 77% for color Doppler US versus 97% for scintigraphy (P = .05). There were no other statistically significant differences between the sensitivities and specificities.

CONCLUSION

Color Doppler US and scintigraphy demonstrate no statistically significant difference in ability to demonstrate testicular torsion in boys with acute scrotal symptoms and indeterminate clinical presentations. Owing to its greater specificity, scintigraphy may help prevent unnecessary surgery when color Doppler US shows equivocal flow.

A Monte Carlo simulation of advanced HIV disease: application to prevention of CMV infection

BACKGROUND

Disagreement exists among decision makers regarding the allocation of limited HIV patient care resources and, specifically, the comparative value of preventing opportunistic infections in late-stage disease.

METHODS

A Monte Carlo simulation framework was used to evaluate a state-transition model of the natural history of HIV illness in patients with CD4 counts below 300/mm3 and to project the costs and consequences of alternative strategies for preventing AIDS-related complications. The authors describe the model and demonstrate how it may be employed to assess the cost-effectiveness of oral ganciclovir for prevention of cytomegalovirus (CMV) infection.

RESULTS

Ganciclovir prophylaxis confers an estimated additional 0.7 quality-adjusted month of life at a net cost of $10,700, implying an incremental cost-effectiveness ratio of roughly $173,000 per quality-adjusted life year gained. Sensitivity analysis reveals that this baseline result is stable over a wide range of input data estimates, including quality of life and drug efficacy, but it is sensitive to CMV incidence and drug price assumptions.

CONCLUSIONS

The Monte Carlo simulation framework offers decision makers a powerful and flexible tool for evaluating choices in the realm of chronic disease patient care. The authors have used it to assess HIV-related treatment options and continue to refine it to reflect advances in defining the pathogenesis and treatment of AIDS. Compared with alternative interventions, CMV prophylaxis does not appear to be a cost-effective use of scarce HIV clinical care funds. However, targeted prevention in patients identified to be at higher risk for CMV-related disease may warrant consideration.

The cost-effectiveness of preventing AIDS-related opportunistic infections

CONTEXT

Multiple options are now available for prophylaxis of opportunistic infections related to the acquired immunodeficiency syndrome (AIDS). However, because of differences in incidence rates as well as drug efficacy, toxicity, and costs, the role of different types of prophylaxis remains uncertain.

OBJECTIVE

To determine the clinical impact, cost, and cost-effectiveness of strategies for preventing opportunistic infections in patients with advanced human immunodeficiency virus (HIV) disease.

DESIGN

We developed a Markov simulation model to compare different strategies for prophylaxis of Pneumocystis carinii pneumonia (PCP), toxoplasmosis, Mycobacterium avium complex (MAC) infection, fungal infections, and cytomegalovirus (CMV) disease in HIV-infected patients. Data for the model were derived from the Multicenter AIDS Cohort Study, randomized controlled trials, and the national AIDS Cost and Services Utilization Survey.

MAIN OUTCOME MEASURES

Projected life expectancy, quality-adjusted life expectancy, total lifetime direct medical costs, and cost-effectiveness in dollars per quality-adjusted life-year (QALY) saved.

RESULTS

For patients with CD4 cell counts of 0.200 to 0.300 x 10(9)/L (200-300/microL) who receive no prophylaxis, we projected a quality-adjusted life expectancy of 39.08 months and average total lifetime costs of $40288. Prophylaxis for PCP and toxoplasmosis with trimethoprim-sulfamethoxazole for patients with CD4 cell counts of 0.200 x 10(9)/L (200/microL) or less increased quality-adjusted life expectancy to 42.56 months, implying an incremental cost of $16000 per QALY saved. Prophylaxis for MAC for patients with CD4 cell counts of 0.050 x 10(9)/L (50/microL) or less produced smaller gains in quality-adjusted life expectancy; incremental cost-effectiveness ratios were $35000 per QALY saved for azithromycin and $74000 per QALY saved for rifabutin. Oral ganciclovir for the prevention of CMV infection was the least cost-effective prophylaxis ($314000 per QALY saved). Results were most sensitive to the risk of developing an opportunistic infection, the impact of opportunistic infection history on long-term survival, and the cost of prophylaxis.

CONCLUSIONS

The cost-effectiveness of prophylaxis against HIV-related opportunistic infections varies widely, but prophylaxis against PCP or toxoplasmosis and against MAC delivers the greatest comparative value. In an era of limited resources, these results can be used to set priorities and explore new alternatives for improving HIV patient care.

The cost-effectiveness of fluconazole prophylaxis against primary systemic fungal infections in AIDS patients

OBJECTIVE

To project the cost-effectiveness of fluconazole for prophylaxis against AIDS-related primary systemic fungal infections.

DESIGN

A Markov model with data from the literature.

PATIENTS

Hypothetical cohort of 100,000 AIDS patients.

INTERVENTION

No prophylaxis, and fluconazole prophylaxis beginning when a patient's CD4 count declined to below 200/mm3, below 100/mm3, or below 50/mm3.

RESULTS

The no-prophylaxis policy was associated with a discounted life expectancy of 28.20 months and direct medical costs of $36,100 per person. The < 200/mm3 strategy increased costs to $40,500 and life expectancy to 28.42 months, producing a ratio of $240,000 per year of life saved (YLS). Compared with the no-prophylaxis and < 200/mm3 policies, the intermediate alternatives were less economically efficient. A reduction in fluconazole's cost from $206 to $80 decreased the ratio to $50,000 for the < 200/mm3 strategy. Doubling fungal infection incidence lowered this ratio to $96,000/YLS.

CONCLUSIONS

Fluconazole prophylaxis is unlikely to be cost-effective unless its cost is lowered, or it is focused on patients in regions endemic for fungal infections.

The cost-effectiveness of HIV testing: accounting for differential participation rates

OBJECTIVE

To understand the impact of differences in participation rates between infected and uninfected individuals on estimates of the cost-effectiveness of HIV screening.

METHODS

Costs per infection detected are modeled as function of both prevalence and serostatus-dependent testing rates. Data from national surveillance surveys, seroprevalence studies, and other sources are employed to suggest the magnitude of results.

RESULTS

Differential participation produces a near-doubling in the estimated cost per infection identified. This result is sensitive to assumptions regarding the benefits of screening for seronegatives.

CONCLUSIONS

Voluntary HIV screening programs may incur prohibitive costs by over-recruiting people at little risk of infection. Failure to account for differential participation can result in over-optimistic cost-effectiveness estimates. However, the relevance of this result--and the significance of both prevalence and participation as cost drivers--is overwhelmed by what is assumed about the benefits conferred to uninfected people by HIV screening.

Estimating CE ratios under second-order uncertainty: the mean ratio versus the ratio of means

Two methods have been presented for estimating cost-effectiveness ratios under conditions of second-order (model) uncertainty: one method estimates a mean ratio of cost to effect (the "mean ratio" approach), and the other estimates a ratio of mean cost to mean effect (the "ratio of means" approach). However, the question of which estimate is theoretically correct has not been formally addressed. The authors show that the "ratio of means" approach follows directly from the theoretical foundations of cost-effectiveness analysis, has attractive internal consistency properties, and is consistent with a simple vector algebra approach to the problem. In contrast, the "mean ratio" approach has not been shown to follow from first principles, is internally inconsistent, and can prescribe economically inefficient choices. It is concluded that the "ratio of means" procedure should be preferred unless persuasive arguments are presented to the contrary.

Why training is the key to successful guideline implementation

The market for pharmacoeconomic analysis is rapidly expanding. Demand for experienced investigators seems to have outpaced the capacity of both the academic community and industry to train qualified practitioners. The result is that many professionals charged with producing and using cost-effectiveness and other drug-related economic evaluation studies may lack the basic skills required to carry out their duties. This, in turn, raises concerns regarding the credibility and integrity of the field as a whole. In our opinion, the adoption of self-imposed practice guidelines is a necessary first step in confronting these issues. However, the power of guidelines to promote responsible practice will be limited by the technical preparation of the analysts charged with adhering to them. A long term solution requires a collaborative commitment, on the part of both the academic community and the private sector, to targeted graduate training in pharmacoeconomic methods, and to the provision of ample opportunities for continuing professional education.

Mathematical programming for the efficient allocation of health care resources

Previous discussions of methods for the efficient allocation of health care resources subject to a budget constraint have relied on unnecessarily restrictive assumptions. This paper makes use of established optimization techniques to demonstrate that a general mathematical programming framework can accommodate much more complex information regarding returns to scale, partial and complete indivisibility and program interdependence. Methods are also presented for incorporating ethical constraints into the resource allocation process, including explicit identification of the cost of equity.

Cost-effectiveness of cancer screening in end-stage renal disease

BACKGROUND

Limited evidence suggests that persons with end-stage renal disease (ESRD) may be at increased risk for malignancy. The appropriateness of screening procedures in this population has not been evaluated.

OBJECTIVE

To determine the relative cost-effectiveness of hypothetical cancer screening programs in the population with ESRD compared with the general population.

METHODS

We performed a cost-effectiveness analysis, employing the declining exponential approximation of life expectancy. Assumptions were put forth to bias the model in favor of cancer screening. Secondary comparisons were made between cancer screening and other interventions targeted to patients with ESRD.

RESULTS

The costs per unit of survival benefit conferred by cancer screening were 1.6 to 19.3 times greater among patients with ESRD than in the general population, depending on age, sex, and race, and assumptions outlined herein. For persons with ESRD, the net gain in life expectancy from a typical cancer screening program was calculated to be 5 days or less. Similar survival gains could be obtained via a reduction of 0.02% or less in the baseline ESRD-related mortality rate.

CONCLUSIONS

These analyses suggest that routine cancer screening in the population with ESRD is a relatively inefficient allocation of financial resources. Direction of funds toward improving the quality of dialysis could attain such an objective at substantially lower cost. Furthermore, these findings highlight the importance of competing risks as a consideration in the evaluation of screening strategies and other interventions targeted to patients with ESRD and to other populations with chronic diseases associated with reduced survival.

Economic evaluation of HIV testing among intravenous drug users. An analytic framework and its application to Italy

We performed an economic evaluation of HIV testing among intravenous drug users (IVDUs) in Italy using the analytical framework of cost-effectiveness analysis. A semi-Markov model was developed to calculate costs and life expectancy of a cohort of IVDUs with and without an annual HIV testing program. We also investigated the incremental cost-effectiveness of a hypothetical early treatment to prolong the life expectancy of HIV-infected asymptomatic subjects by 1 year. The testing program is cost saving in the low prevalence scenario (0.05), and costs L 14,000,000 (US $8,400) and L 55,800,000 (US $33,500) per year of life saved in areas of medium (0.3) and high (0.6) prevalence, respectively. The incremental cost-effectiveness of the hypothetical early treatment may compare favorably with other health care interventions. The program may be considered a cost-effective procedure in low and medium prevalence areas. Where prevalence is high, more evidence about the magnitude of the behavior change is needed. In these areas, the availability of an effective early treatment may become the economic rationale for implementing such a program.

The FDA and regulation of cost-effectiveness claims

The Food and Drug Administration (FDA) has issued draft guidelines that would require more rigorous standards for making pharmacoeconomic claims. This paper critiques the guidelines and explores the objectives of market regulation for health-related cost and effectiveness information on pharmaceutical products. It argues that the FDA should proceed with caution and flexibility. In particular, regulations should recognize the potential usefulness of pharmacoeconomic information in helping health care decisionmakers make better-informed choices. They also should acknowledge the enhanced ability of those using the information to evaluate pharmacoeconomic studies and the degree to which the various players in the market can impose their own regulatory discipline.

The epidemiological and economic consequences of AIDS clinical trials

The Food and Drug Administration (FDA) must manage the delicate balance between speed and safety in the evaluation and approval of new drugs. To explore how these competing obligations might be formalized with respect to the AIDS epidemic, we present a simple decision-theoretic optimization model of the clinical trials process against a backdrop of HIV transmission. Our framework sheds light on such issues as the economic consequences of decisions, the potential savings of a new therapy, the costs to society of delay, the value of better information, and how and when to undertake a clinical trial. We believe that this article represents a first effort to unravel the tangled web of epidemiological, economic, and statistical considerations that plague this policy issue.