Objective: To determine the effect of BMI on clinical response to the treatment of cIAI.

Methods: This is a post hoc analysis of microbiologically evaluable patients at early follow up assessment (EFA), using the data from a prospective randomized trial of ertapenem vs. piperacillin tazobactam for the treatment of cIAI. Patients were grouped into either normal (<30 kg/m2) or high (≥30 kg/m2 ) BMI to determine the effect of BMI on the proportion of favorable clinical response. . The proportions in the normal and high BMI categories were compared with a 95% exact confidence interval on the difference within each treatment group.

Results: The microbiologically evaluable population at EFA included 231 patients, 123 patients for the ertapenem and 108 patients for the piperacillin/tazobactam treatment groups. The proportion of patients with a favorable clinical response assessment at EFA by BMI and treatment group is shown in the table below. 12 patients did not have BMI recorded and were excluded. Patients receiving piperacillin tazobactam had a nominally lower response rate in the high BMI group.

Proportion of Patients With Favorable Clinical Response Assessments—at EFA
(Microbiologically Evaluable Population)

	BMI <30 (A)	BMI ≥ 30 (B)	Difference (A-B)
Treatment Group	n/N (%)	n/N (%)	% (95% CI)	p value 1
Ertapenem	69/86 (80%)	26/32 (81%)	-1% (-22%, 19%)	0.93
Pip Tazo	67/78 (86%)	15/23 (65%)	21% (-1%, 47%)	0.08

*n=favorable clinical response, N=number in subgroup, exact test on difference of two proportions

Conclusion: Differing antibiotic regimens may yield different clinical response rates for cIAI in patients with a high BMI. Due to the limitations of post hoc analysis and small subgroups, further study is needed.