We retrospectively searched our patient database for the records of all adult recipients of a single lung, bilateral lung, or heart-lung transplant at Mayo Clinic, Rochester, Minnesota, from January 1, 2000, through January 13, 2012. We included those with biobanked pre-transplant plasma samples and those with CT that covered the L3 vertebral level, performed within 365 days before transplant. We excluded those who did not provide Minnesota Research Authorization or were undergoing repeat transplant.
The Mayo Clinic Institutional Review Board approved this project and waived consent because of minimal risk. This study complies with the ethical Declarations of Helsinki and Istanbul.
We abstracted all demographic and patient-related information from the electronic medical records. Weight and height measurements were abstracted from the pretransplant period as close to the time of transplant as possible. We used the banked plasma samples from each patient to measure both serum creatinine concentration (in mg/dL) with the Roche enzymatic method (Roche Hitachi Modular P analyzer with the Roche Creatinine plus assay; Hoffmann–La Roche) and cystatin C concentration (in mg/L) with the cystatin C immunoturbidimetric assay (Gentian). If multiple pretransplant samples were available, we chose the sample closest to the date of the CT. SI was calculated as (serum creatinine value/cystatin C value) × 100.
To measure muscle mass, we used sliceOmatic software, version 5.0 (TomoVision) with the available CT images to determine the abdominal skeletal muscle cross-sectional surface area (SA) at the level of the first to third lumbar vertebrae (L1 to L3) (23 (link), 24 (link)). The software uses tissue radiodensity to identify muscle (Hounsfield units of −40 to +170) and can be manually corrected if needed. Muscles measured at this site include the rectus abdominis, internal and external obliques, psoas, quadratus lumborum, erector spinae, and the transversus abdominis. Prior studies have demonstrated that measurements at the L3 level are precise surrogates for total body muscle mass (25 (link), 26 (link)). Measurements were performed in duplicate and averaged. The interrater agreement has previously been demonstrated to be excellent. Kelm et al (1 (link)) reported the interrater Pearson correlation coefficient (r) for muscle index measurements to be 0.998 (95% CI, 0.997–0.999) (20 ). We calculated body surface area with the Mosteller formula: body surface area in m2 = (height in cm × weight in kg/3,600)1/2. The skeletal muscle index (cm2/m2) was computed as the ratio of the SA at the L3 level to body surface area.
The Mayo Clinic Institutional Review Board approved this project and waived consent because of minimal risk. This study complies with the ethical Declarations of Helsinki and Istanbul.
We abstracted all demographic and patient-related information from the electronic medical records. Weight and height measurements were abstracted from the pretransplant period as close to the time of transplant as possible. We used the banked plasma samples from each patient to measure both serum creatinine concentration (in mg/dL) with the Roche enzymatic method (Roche Hitachi Modular P analyzer with the Roche Creatinine plus assay; Hoffmann–La Roche) and cystatin C concentration (in mg/L) with the cystatin C immunoturbidimetric assay (Gentian). If multiple pretransplant samples were available, we chose the sample closest to the date of the CT. SI was calculated as (serum creatinine value/cystatin C value) × 100.
To measure muscle mass, we used sliceOmatic software, version 5.0 (TomoVision) with the available CT images to determine the abdominal skeletal muscle cross-sectional surface area (SA) at the level of the first to third lumbar vertebrae (L1 to L3) (23 (link), 24 (link)). The software uses tissue radiodensity to identify muscle (Hounsfield units of −40 to +170) and can be manually corrected if needed. Muscles measured at this site include the rectus abdominis, internal and external obliques, psoas, quadratus lumborum, erector spinae, and the transversus abdominis. Prior studies have demonstrated that measurements at the L3 level are precise surrogates for total body muscle mass (25 (link), 26 (link)). Measurements were performed in duplicate and averaged. The interrater agreement has previously been demonstrated to be excellent. Kelm et al (1 (link)) reported the interrater Pearson correlation coefficient (r) for muscle index measurements to be 0.998 (95% CI, 0.997–0.999) (20 ). We calculated body surface area with the Mosteller formula: body surface area in m2 = (height in cm × weight in kg/3,600)1/2. The skeletal muscle index (cm2/m2) was computed as the ratio of the SA at the L3 level to body surface area.
