Single-dose versus multiple-dose antibiotic prophylaxis for the surgical treatment of closed fractures

Figures & data

Table 1.  Model variables

Variable	Base case	Range	References
Incidence of SSI
Single-dose prophylaxis	0.025	0.01–0.06	Garotta et al. 1991, Gatell et al. 1987, Slobogean et al. 2008
Superficial	0.66	^a	Slobogean et al. 2008
Deep	0.34	0.3–0.6	Slobogean et al. 2008
Multiple-dose prophylaxis	0.02	0.01–0.06	Garotta et al. 1991, Slobogean et al. 2008, Ali and Raza 2006
Superficial	0.57	^a	Slobogean et al. 2008
Deep	0.43	0.3–0.6	Slobogean et al. 2008
Incidence of Abx-related C. difficile
Risk per dose of 1st generation cephalosporin	0.00028	0.0001–0.0013	Anand et al. 1994
Doses to treat superficial SSI	40	28–56
Risk of C. difficile	0.011	0.008–0.016
Doses to treat deep SSI	126	84–168
Risk of C. difficile	0.035	0.023–0.047
Costs (2007 USD)
ORIF ankle fracture	2,481	2,000–10,000	Bhandari et al. 2004
Preparation and dose of cefazolin	9	5–15	Garrelts et al. 1994 ^b
Single-dose prophylaxis	9	5–15
Multiple-dose prophylaxis	36	20–60
Superficial SSI	2,319	500–5,000	Zoutman et al. 1998
Deep SSI	5,255	3,000–15,000	Zoutman et al. 1998
C. difficile	4,689	2,270–14,717	Kyne et al. 2002, O'Brien et al. 2007
Quality Adjusted Life Days (QALD)
Ankle fracture	272	204–285	Bhandari et al. 2004
C. difficile	268	124–284	Kyne et al. 2002, Pepin et al. 2005
Superficial SSI	272	204–285
Superficial SSI and C. difficile	268	124–284	Kyne et al. 2002, Pepin et al. 2005
Deep SSI	267	123–283	Kuntz et al. 2000
Deep SSI and C. difficile	263	122–282	Kyne et al. 2002, Pepin et al. 2005, Kuntz et al. 2000

^a 1 – probability of deep infection.

^b cost obtained from institution's pharmacy.

SSI: surgical site infection.

Figure 1.  Decision tree representing the single- or multiple-dose prophylaxis decision for the surgical treatment of a closed fracture. The probability of an event occurring is listed beneath each respective branch.

Table 2. Health-related quality of life adjustments

Event	Health state (utilities)	QALD
Ankle fracture	0.34 for 30 days0.78 for remainder of time horizon	272
C. difficile	0.30 for 7 days0.34 for 30 days0.78 for remainder of time horizon	268
Superficial SSI	0.34 for 30 days0.78 for remainder of time horizon	272
Superficial SSI and C. difficile	0.30 for 7 days0.34 for 30 days0.78 for remainder of time horizon	268
Deep SSI	0.30 for 10 days0.34 for 30 days0.78 for remainder of time horizon	267
Deep SSI and C. difficile	0.25 for 7 days0.30 for 10 days0.34 for 30 days0.78 for remainder of time horizon	263

QALD: quality-adjusted life-days;

SSI: surgical site infection.

Table 3. Base case analysis

Prophylaxis	Cost ($)	QALD	ICER
Single	2,576.49	272	–
Multiple	2,595.84	272	Dominated

QALD: quality-adjusted life-days;

ICER: incremental cost-effectiveness ratio.

Figure 2.  Results of two-way sensitivity analysis. The incidence of surgical site infection (A) and the proportion of deep wound infection (B) for each prophylaxis strategy is varied throughout the range described in Table 1.

Figure 3.  Results of Monte Carlo probabilistic sensitivity analysis. The incremental cost-effectiveness ratio for multiple-dose prophylaxis compared to the single-dose strategy is shown. A “willingness to pay” threshold of $137 per incremental QALD (dashed line) and the 95% confidence interval (ellipse) are also shown.

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