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Research
Optimizing Treatment of Antimicrobial-resistant
Neisseria gonorrhoeae
Kakoli Roy,*
Susan A. Wang,* and Martin I. Meltzer*
*Centers for Disease Control and Prevention, Atlanta, Georgia, USA
Appendix 2. Average and Incremental
Cost-effectiveness Analysis
Average and incremental cost-effectiveness analyses conducted for a hypothetical
cohort of 1 million women treated with each of the 4 alternative strategies
is presented in the Table, below. Average cost-effectiveness
was estimated as the cost per case successfully treated with a given strategy
compared to the baseline strategy. Incremental cost-effectiveness ratio
was estimated as the additional cost per additional case of pelvic inflammatory
disease (PID) averted for a strategy compared to the next less effective
strategy.
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Appendix 2 Table. Average
and incremental cost-effectiveness analysis* for a cohort of 1 million
women (prevalence of ciprofloxacin resistance = 0.1%)
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Alternative strategies (from least to most effective)
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Expected number of cases of PID†
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Total cost (intervention + sequelae)
(US $1,000s)
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Incremental cost
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Average cost-effectiveness‡ ratio
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Incremental cost-effectiveness ratio§
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Neisseria gonorrhoeae prevalence = 0.01
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ST1: ciprofloxacin + culture
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787
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$26,000
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Baseline
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Baseline
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ST3: ceftriaxone + culture
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787
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$26,210
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$210,000
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(Strongly dominated)¶
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(Strongly dominated)¶
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ST2: ciprofloxacin + nonculture
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695
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$32,760
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$6,760,000
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$356,087
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$73,478
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ST4: ceftriaxone + nonculture
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694
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$34,070
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$8,070,000
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$366,344
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$8,070,000
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N. gonorrhoeae prevalence = 0.10
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ST1: ciprofloxacin+ culture
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7,874
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$62,090
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(Strongly dominated)#
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(Strongly dominated)#
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ST3: ceftriaxone + culture
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7,871
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$62,090
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(Strongly dominated)#
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(Strongly dominated)#
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ST2: ciprofloxacin + nonculture
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6,953
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$61,860
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Baseline
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Baseline
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ST4: ceftriaxone + nonculture
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6,941
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$63,420
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$1,560,000
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$7,046,000
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$173,000
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*Applies baseline values to all variables, other
than prevalence of N. gonorrhoeae.
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†PID (pelvic inflammatory disease) includes cases
of both symptomatic and asymptomatic PID and sequelae. If gonorrhea
prevalence is 1%, 1,600 cases of PID would result in the absence
of any intervention. If the prevalence of gonorrhea is 10%, the
number of PID cases would be 16,000. However, "do nothing"
is not a feasible strategy for a clinic as it has already committed
to treatment of sexually transmitted diseases.
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‡Cost-effectiveness ratios are expressed as cost
(in thousands of dollars) per additional case of PID prevented compared
to the baseline strategy.
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§ Incremental cost-effectiveness ratios are expressed
as cost (in thousands of dollars) per additional case of PID prevented
compared to the least expensive strategy listed in the preceding
row.
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¶A strongly dominated strategy is one that is more
expensive than an equally or a more effective strategy. For example,
ST3 is strongly dominated by ST1 as it is equally effective but
more expensive than ST1.
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#Both ST1 and ST3 are strongly dominated by ST2
as they are both strategies that are less effective but more expensive
than ST2.
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Cost per case prevented varies depending on prevalence of gonorrhea (PRGC)
and prevalence of ciprofloxacin resistance (PRCIPRO). Using
base-case estimates], and assuming that PRGC is 1% and PRCIPRO
is 0.1%, the resulting cost-effectiveness ratios (CERs) indicate that
ST3 (ceftriaxone + culture) is strongly dominated by ST1 (ciprofloxacin
+ culture). The costs per case of PID prevented compared to the baseline
(ST1) for ST2 (ciprofloxacin + nonculture) and ST4 (ceftriaxone + nonculture)
are $356,087 and $366,344, respectively. Incremental cost-effectiveness
analysis indicates that ST2 compared to ST1 costs an additional $73,478
per case prevented, and ST4 compared to ST2 costs an additional $8,070,000
per case prevented. However, if PRGC is 10%, even with PRCIPRO
at 0.1%, ST1 and ST3 are strongly dominated by ST2. Thus, nonculture-based
strategies (ST2 and ST4) are more cost-effective than culture-based strategies
(ST1 and ST3), and the cost per case of PID prevented by ST4 compared
to ST2 is $173,000.
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