Assessment of radiofrequency device sensitivity for the detection of retained surgical sponges in patients with morbid obesity.

Hypothesis: Retained surgical sponges are serious medical errors that result in negative patient outcomes. A radiofrequency (RF) mat for the operating room bed has recently been introduced to detect the presence of a retained surgical sponge. The study objectives were to evaluate the sensitivity and specificity of the RF mat for the detection of surgical sponges through the torso of individuals with varying body habitus and to compare the sensitivity of the RF mat with that of the RF wand. We hypothesized that the sensitivity and specificity of the RF technology would be comparable to published findings of the manual sponge count by operating room personnel.

Design: A prospective, crossover, double-blinded study design was used. Participants served as their own controls. SETTING Large Midwestern academic medical center.

Participants: In total, the first phase of the study enrolled 203 participants, including 129 (63.5%) with morbid obesity. One hundred seventeen of 203 participants were also enrolled in the second phase of the study.

Main outcome measures: The study participants reclined in a supine position on top of an RF mat. Four surgical sponges were sequentially placed on top of the torso in locations approximating the abdominal quadrants. The torso was scanned for sponges. In a subset of participants, 4 surgical sponges were sequentially placed underneath the torso, and an RF wand was passed over the abdomen.

Results: Overall, 812 readings were obtained with the RF mat, and 468 readings were obtained with the RF wand. Twelve false-negative readings were obtained with the RF mat, exclusively in participants with super morbid obesity (body mass index [calculated as weight in kilograms divided by height in meters squared] >50.0). Overall, the sensitivity of the RF mat was 98.1%, and the specificity of the RF mat was 100.0%. In the subset of 117 participants in whom the RF wand was also used, the sensitivity and specificity of the wand were each 100.0%.

Conclusions: The sensitivity and specificity of RF device technology are much higher than those of surgical sponge counts or published findings on the use of intraoperative radiographs to identify retained surgical sponges. The RF wand is more sensitive than the RF mat in individuals with morbid obesity.