SAN DIEGO (FRONTLINE MEDICAL NEWS) – Patients hospitalized for gram-negative bacteremia who weighed more than 70 kg had improved 30-day mortality, compared with those who weighed 70 kg or less, results from a single-center study showed.

“This study is a first step to determine the impact of low body weight on mortality in patients with bloodstream infections due to gram negative pathogens,” Ronald G. Hall II, Pharm.D., MSCS, said in an interview in advance of the annual Interscience Conference on Antimicrobial Agents and Chemotherapy. “It should reinforce that clinicians need to aggressively treat patients who weigh less than 70 kg due to the increased risk of death. However, more data are needed to confirm this finding and determine the causes of this association.”

For the study, Dr. Hall, of the Texas Tech University Health Sciences Center School of Pharmacy, Dallas, and his associates retrospectively evaluated 324 patients admitted to a community teaching hospital for gram-negative bacteremia who received at least two days of empiric antibiotic therapy. They used univariate and multivariable logistic regression analysis to compare the 30-day mortality of patients with a total body weight of 70 kg or less with those weighing more than 70 kg.

Of the 324 patients, 184 (57%) weighed more than 70 kg. The 30-day mortality rate was 16.3% for patients who weighed 70 kg or less, compared with 10.5% for their counterparts who weighed more than 70 kg. This difference did not reach statistical significance on univariate analysis (odds ratio 0.67 for the higher body weight patients), but it did reach statistical significance on multivariable analysis (OR .43 for the higher body weight patients). Other factors that remained significant in the multivariable model were a cancer diagnosis (OR 2.55) and a Pitt bacteremia score of 4 or greater (OR 16.83).

“This study is the first, to our knowledge, to evaluate the impact of low total body weight on mortality in patients with bloodstream infections due to gram-negative pathogens,” Dr. Hall said. “Other investigators have found similar results previously evaluating the impact of underweight patients using body mass index (BMI). However, BMI uses both height and weight, with height being taken into a greater account (kg/m2) which may be misleading on the impact of weight.”

He acknowledged certain limitations of the study, including its single-center design. “A larger cohort will help improve our confidence in this finding by being able to control for more potential confounding variables,” he said.

Dr. Hall disclosed that he is a scientific advisor for Genentech. The other researchers reported having no financial disclosures.