One- and two-way sensitivity analyses examined how the prevalence of male infection and the cost of the LCR assay affected overall strategy cost. As prevalence increased, total program costs for each strategy differed. At a prevalence of 3%, no screening cost $4.47, LE-LCR cost $34.38, and LCR cost $57.80 per screened male. At a prevalence of 5%, no screening cost $7.44, LE-LCR cost $36.58, and LCR cost $59.20 per screened male. At a prevalence of 10%, no screening cost $14.89, LE-LCR cost $42.08, and LCR cost $62.72 per screened male. The LCR strategy became less expensive than LE-LCR above a prevalence of 60% and became less expensive than no screening above a prevalence of 70%.
One-way sensitivity analyses examined how the prevalence of male infection and the cost of the LCR assay affected overall strategy effectiveness. As shown in Figure 4, at any prevalence of male infection, the LCR strategy was more effective in preventing cases of PID than was the LE-LCR strategy, which in turn was more effective than the no screening strategy. Varying the cost of the LCR assay had no effect on program effectiveness.
At 5% prevalence, LE-LCR cost $12,041 to prevent an additional case of PID over no screening, and LCR cost $21,750 to prevent an additional case over LE-LCR. However, if the if the cost of the LCR assay fell to $18 or less, or if the prevalence of infection increased to 49%, the LCR strategy cost less to prevent an additional case of PID than the LE-LCR strategy.
We assessed the incremental cost-effectiveness of a variety of scenarios that account for some important analytic limitations. Inclusion of indirect costs or costs to private payors increased the cost of all strategies but did not significantly change the incremental cost-effectiveness of the strategies. When additional C trachomatis–associated sequelae (endometritis, perihepatitis, and proctitis) were included, the cost of the no screening strategy increased by 55% to $11.55 per male screened, LE-LCR increased by 6% to $38.78, and LCR increased by 2% to $60.59. In incremental analysis, LE-LCR became cost-saving over no screening at or above a prevalence of 41%, and the LCR strategy became cost-saving over LE-LCR at or above a prevalence of 44%. When costs of a clinic visit associated with screening in traditional healthcare settings were removed, LE-LCR became cost-saving over no screening at a prevalence of 23%, but the LCR strategy did not become cost-saving over the LE-LCR strategy until a prevalence of 62%. When costs from a recent economic evaluation of screening asymptomatic women were used, 48 both the LE-LCR and the LCR strategy became cost-saving at a prevalence of infection among men of 4% or higher.
We found that at a prevalence of chlamydial infection of 5% among asymptomatic men, prescreening urine for LE, followed by confirmatory testing with urine-based LCR, was the most cost-effective strategy. Relative to no screening, LE-LCR resulted in 242 fewer cases of PID per 100,000 males screened and cost $29.14 per male tested. While testing all men with LCR prevented more chlamydia-associated sequelae than LE-LCR, the additional cost was substantial ($22.62 per man screened). In sensitivity analysis, the cost of the LCR assay and the prevalence of C trachomatis infection in males critically impacted outcomes. In order for a strategy using only urine LCR screening to be more efficient than LE-LCR at the chlamydia prevalence in our base-case analysis (5%), the cost of the LCR assay needed to decline to $18 or less.
In general, our results concur with those of other investigators. Genc and colleagues 9 estimated that screening asymptomatic men with urine LE testing confirmed by a specific enzyme immunoassay (EIA) test was more cost-effective than screening with only EIA. Two other large studies also concluded that applying an initial nonspecific screening test (such as an LE test) followed by specific testing was the most cost-effective approach to screening asymptomatic men. 6,7 Our analysis extends this work in several ways. We evaluated the use of a nucleic acid amplification assay and, of critical importance, included costs of managing female partners of infected men. We accounted for outcomes of symptomatic and subclinical PID and incorporated new treatment protocols, including the use of methotrexate for ectopic pregnancy. All direct costs associated with chlamydial infection, not just the cost of diagnostic tests, were included (such as office visits, hospital fees, surgical procedures, laboratory work, medication). Finally, we performed extensive sensitivity analyses on cost variables to ensure applicability of the analysis to a wide array of settings and payor types.
Our study has several limitations. First, the validity of our model depends on the accuracy of the incorporated probabilities. Extensive sensitivity analyses mitigated some of this uncertainty. Second, our analysis was done from the perspective of the healthcare payor. An analysis from the societal perspective would include nonmedical direct costs, indirect costs, and intangible costs. Inclusion of indirect costs increased the overall cost of each strategy but did not significantly change the incremental cost of preventing an additional case of PID for either strategy. Third, we chose Medicaid reimbursements to Washington state providers and facilities. These cost values are likely to be lower than the cost to private health plans. Raising these estimates to more substantially represent private fee schedules did not change our general conclusions. Fourth, we did not include all C trachomatis–associated outcomes, such as urethritis, bartholinitis, endometritis, and perihepatitis in women and proctitis, prostatitis, and Reiter syndrome in men. Studies have also demonstrated an association between chlamydial infection and low birth weight, postpartum endometritis, premature rupture of membranes, and chorioamnionitis;3 enhanced risk of HIV transmission;49 and cervical cancer. 50 Inclusion of such events would favor the LCR strategy, since more of these expensive outcomes would be avoided.
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