Predictors of efficacy and health resource utilization in treatment of complicated intra-abdominal infections: evidence for pooled clinical studies comparing tigecycline with imipenem-cilastatin.

BACKGROUND

Duration of intravenous (IV) treatment, surgical/radiologic interventions for infection control, and hospital length of stay (LOS) are important cost considerations in complicated intra-abdominal infections (cIAIs).

METHODS

Data were pooled from two multinational, double-blind studies conducted in hospitalized adults with cIAIs who were randomized (1:1) to receive tigecycline (100 mg IV initial dose then 50 mg IV every 12 h) or imipenem-cilastatin (500 mg IV every 6 h) for 5 to 14 days in order to assess tigecycline safety and efficacy. This report focuses on developing predictors of cure and health care resource utilization, including the need for repeat surgical/radiologic interventions, duration of IV antibiotic therapy, and hospital LOS. Multiple regression models were applied for each of the above outcomes, incorporating both baseline and on-treatment potential covariates. Logistic modeling was used for categorical outcomes (cure; repeat surgical/radiologic interventions) and least squares modeling for continuous outcomes (duration of IV antibiotic therapy; LOS). Stepwise selection was used to retain only those predictors found to be significant (p < 0.05) independent risk factors.

RESULTS

The most common causative pathogen was Escherichia coli (63.0%), with 63.3% of the patients exhibiting polymicrobial infections. The most common cIAI diagnosis was complicated appendicitis (51.9%). Lack of clinical cure (+ 6.1 days; p < 0.0001), perforation of the intestine (+3.7 days; p < 0.0001), an Acute Physiology and Chronic Health Evaluation (APACHE) score >15 (+3.1 days; p=0.039), abnormal plasma sodium concentration (+3.7 days; p=0.026), and repeat surgical/radiologic intervention (+2.2 days; p=0.0097) were identified as key risk factors for longer LOS. Inadequate source control was associated with reduced odds of cure, longer IV treatment duration (+1.5 days; p=0.007), and longer LOS. The treatment groups did not differ in terms of LOS, IV treatment duration, or clinical cure.

CONCLUSION

Tigecycline was similar to imipenem-cilastatin in terms of both efficacy and health resource utilization. Risk factors identified in this study for both outcome measures are offered as support for guiding clinical practice.