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Background and Objective: HIV chemoprophylaxis may be a future prevention strategy to help control the global epidemic of HIV/AIDS. Safety and efficacy trials of two agents are currently underway. We assess the expected number of HIV cases prevented and cost-effectiveness of a hypothetical HIV chemoprophylaxis program among men who have sex with men in a large US city., Design and Methods: We developed a stochastic compartmental mathematical model using HIV/AIDS surveillance data to simulate the HIV epidemic and the impact of a 5-year chemoprophylaxis program under varying assumptions for epidemiological, behavioral, programmatic and cost parameters. We estimated program effectiveness and costs from the perspective of the US healthcare system compared with current HIV prevention practices. The main outcome measures were number of HIV infections prevented and incremental cost per quality-adjusted life-years saved., Results: A chemoprophylaxis program targeting 25% of high-risk men who have sex with men in New York City could prevent 780 (4%) to 4510 (23%) of the 19 510 HIV infections predicted to occur among all men who have sex with men in New York City in 5 years. More than half of prevented infections would be among those not taking chemoprophylaxis but who benefit from reduced HIV prevalence in the community. Under base-case assumptions, incremental cost was US$ 31 970 per quality-adjusted life-years saved. The program was cost-effective under most variations in efficacy, mechanism of protection and adherence., Conclusion: HIV chemoprophylaxis among high-risk men who have sex with men in a major US city could prevent a significant number of HIV infections and be cost-effective.

Vasospasm is the leading cause of death and disability in patients with aneurysmal subarachnoid hemorrhage (SAH). Transcranial Doppler ultrasonography (TCD) can detect the arterial narrowing noninvasively, but the sensitivity and specificity of this technique have not been reported in a population of patients with a high frequency of angiographic vasospasm. In this study, 34 consecutive patients with SAH undergoing angiography during the period of risk for vasospasm had technically adequate TCD examinations within 24 hours of the angiogram. Using a mean flow velocity of 120 cm/sec and above as indicative of vasospasm, TCD correctly detected angiographic vasospasm in 17 patients; there were no false positives. It correctly determined that 5 patients did not have vasospasm, whereas there were 12 false negatives. False negatives were frequently due to angiographic vasospasm involving vessels not assessable by TCD. The correlation between mean flow velocity and the angiographic residual lumen diameter of the middle cerebral artery was statistically significant. These data suggest that TCD is a highly specific (100%), but less sensitive (58.6%) test for the detection of angiographic vasospasm following SAH. Confirmatory angiography may be avoided if the TCD study is positive, but additional studies may be necessary if the clinical picture is suspicious and the TCD study is negative.