Performance of CT-based low skeletal muscle index, low mean muscle attenuation, and bioelectric impedance derived low phase angle in the detection of an increased risk of nutrition related mortality.

BACKGROUND & AIMS: The aim of this study was to evaluate in a head to head comparison the performance of bioimpedance derived low phase angle (PA), CT-based low skeletal muscle index (SMI) and low mean muscle attenuation (MA), and Pandora Score (PS) to detect an increased nutrition related mortality in hospitalized patients.

METHODS

A total of 7736 patients were hospitalized in Dessau community hospital (Nov 11, 2016-Feb 05, 2017). In 227/7736 patients an abdominal CT scan was obtained and low values (below threshold) of skeletal muscle index (SMI) and mean muscle attenuation (MA) were obtained at L3 level using Slice-O-Matic. In 180/227 patients, malnutrition screening (NRS-2002 ≥ 3), determination of low PA (<5th percentile) and calculation of 30-day mortality risk (PS ≥ 5%) were done within 6 days after the CT scan.

RESULTS

PA was low in 116 (64%), SMI was low in 95 (53%), and MA was below threshold in 137 (77%) patients. Using hospital mortality (8.3%) as a gold standard, low SMI, low MA, or low PA showed high sensitivity (SMI 93.3%; MA 86.7%; PA 86.7%) and high negative predictive (NPV) values (SMI 98.9%; MA 95.3%; PA 96.9%) and improved specificity (NRS + SMI 65.5%; NRS + MA 50.3%; NRS + PA 50.3%) when combined with the criterion NRS ≥ 3. Using hospital mortality as a gold standard, a PS ≥ 36 (predicted mortality ≥ 5%) showed a sensitivity of 73.3%, a specificity of 62.2% and an NPV of 96.4%. PS predicted mortality was ≥5% in 70 (39%) patients and was higher (median 5.2%; IQR: 2.8; 11.8 vs 1.7%; IQR: 1.0; 2.8; p < 0.001) in patients with a low PA and this was also observed for low vs normal SMI (median 5.7%; IQR: 2.6; 11.1 vs 2.7%; IQR:1.4;5.5; p < 0.001) but not for low vs normal MA (median 3.9%; IQR: 2.1; 8.8 vs 3.4%; IQR: 2.0; 8.1; ns).

CONCLUSION

Determination of phase angle < 5th percentile is a convenient non-invasive and inexpensive bedside method with high sensitivity and a high negative predictive value to detect patients at risk of nutrition related mortality with a performance comparable to CT derived skeletal muscle index or mean muscle attenuation.