Table 1. Baseline Characteristics at Time of First Liver Biopsy.
| Unweighted | Weighteda | |||||
|---|---|---|---|---|---|---|
| Bariatric surgery | Nonsurgical control | Standardized differenceb |
Bariatric surgery | Nonsurgical control | Standardized differenceb |
|
| No. of patients | 650 | 508 | ||||
| Liver biopsy | ||||||
| Median date | 7/27/2011 | 6/15/2011 | 0.13 | 7/08/2011 | 5/26/2011 | 0.20 |
| IQR | 12/22/2009-12/18/2013 | 9/20/2008-8/02/2014 | 12/01/2009-12/03/2013 | 8/22/2008-7/08/2014 | ||
| Demographics | ||||||
| Sex, No. (%) or % | ||||||
| Female | 436 (67.1) | 304 (59.8) | 0.15 | 62.9 | 62.9 | 0c |
| Male | 214 (32.9) | 204 (40.2) | 37.1 | 37.1 | ||
| Age, median (IQR), y | 49.0 (40.5 to 57.0) | 50.8 (41.0 to 58.3) | −0.06 | 49.0 (41.0 to 57.0) | 50.2 (40.5 to 58.1) | 0c |
| BMI, median (IQR)d | 45.8 (41.2 to 53.1) | 35.7 (32.8 to 39.7) | 1.41 | 45.7 (41.2 to 52.8) | 36.0 (32.9 to 39.9) | 2.09 |
| Weight, median (IQR), kg | 128.8 (112.2 to 152.4) | 103.7 (91.7 to 115.5) | 1.09 | 129.0 (112.3 to 153.4) | 103.9 (91.6 to 115.4) | 1.67 |
| Race, No. (%) or % | ||||||
| American Indian | 3 (0.5) | 0 | 0.20 | 0.3 | 0 | 0.20 |
| Asian | 0 | 2 (0.4) | 0 | 0.4 | ||
| Black | 59 (9.1) | 21 (4.1) | 9.3 | 4.0 | ||
| Multiracial | 11 (1.7) | 6 (1.2) | 1.7 | 1.2 | ||
| White | 577 (88.8) | 479 (94.3) | 88.7 | 94.4 | ||
| Annual zip code income, median (IQR), $e | 54 821 (46 110 to 69 125) | 60 230 (46 873 to 73 697) | −0.23 | 55 182 (46 110 to 69 125) | 60 095 (46 873 to 72 122) | −0.31 |
| Smoking status, No. (%) or % | ||||||
| Never | 346 (53.2) | 263 (51.8) | 0.11 | 52.5 | 52.5 | 0c |
| Former | 260 (40.0) | 194 (38.2) | 39.1 | 39.1 | ||
| Current | 44 (6.8) | 51 (10.0) | 8.4 | 8.4 | ||
| Cleveland Clinic location, No. (%) or % | ||||||
| Florida | 6 (0.9) | 25 (4.9) | 0.24 | 1.0 | 4.9 | 0.23 |
| Ohio | 644 (99.1) | 483 (95.1) | 99.0 | 95.1 | ||
| Medical history, No. (%) or %f | ||||||
| CCI, median (IQR)g | 3.0 (2.0 to 4.0) | 2.0 (1.0 to 4.0) | 0.23 | 3.0 (2.0 to 4.0) | 2.0 (1.0 to 4.0) | 0.32 |
| Hypertension | 535 (82.3) | 241 (47.4) | 0.78 | 83.0 | 46.9 | 0.82 |
| Dyslipidemia | 479 (73.7) | 241 (47.4) | 0.56 | 73.9 | 46.3 | 0.59 |
| Type 2 diabetes | 330 (50.8) | 169 (33.3) | 0.36 | 40.6 | 40.6 | 0c |
| Heart failure | 39 (6.0) | 9 (1.8) | 0.22 | 6.1 | 1.7 | 0.23 |
| Coronary artery disease | 35 (5.4) | 21 (4.1) | 0.06 | 6.1 | 4.2 | 0.08 |
| Cerebrovascular disease | 13 (2.0) | 9 (1.8) | 0.02 | 1.9 | 1.4 | 0.04 |
| Medication history, No. (%) or % | ||||||
| Antihypertensive | 511 (78.6) | 310 (61.0) | 0.39 | 79.0 | 60.2 | 0.42 |
| Lipid-lowering | 354 (54.5) | 179 (35.2) | 0.39 | 54.4 | 34.9 | 0.40 |
| For diabetes | ||||||
| Not insulin | 343 (52.8) | 150 (29.5) | 0.49 | 49.4 | 30.8 | 0.39 |
| Insulin | 178 (27.4) | 43 (8.5) | 0.51 | 27.6 | 8.2 | 0.52 |
| Vitamin E | 39 (6.0) | 37 (7.3) | −0.05 | 6.2 | 7.3 | −0.04 |
| Clinical and laboratory data, median (IQR) h | ||||||
| Systolic BP, mm Hge | 136 (123 to 148) | 132 (121 to 142) | 0.18 | 136 (123 to 148) | 131 (121 to 143) | 0.24 |
| Diastolic BP, mm Hge | 73 (65 to 83) | 77 (68 to 84) | −0.19 | 73 (65 to 83) | 77 (68 to 84) | −0.27 |
| Albumin, g/dLe | 4.3 (4.1 to 4.5) | 4.4 (4.1 to 4.6) | −0.08 | 4.3 (4.1 to 4.5) | 4.4 (4.1 to 4.6) | −0.11 |
| Bilirubin, mg/dLe | 0.5 (0.4 to 0.6) | 0.5 (0.4 to 0.7) | −0.05 | 0.5 (0.4 to 0.6) | 0.5 (0.3 to 0.7) | −0.04 |
| Creatinine, mg/dLe | 0.8 (0.7 to 1.0) | 0.8 (0.7 to 0.9) | 0.15 | 0.8 (0.7 to 1.0) | 0.8 (0.7 to 0.9) | 0.35 |
| Hemoglobin A1c, %e,i | 7.3 (6.5 to 8.6) | 6.8 (6.0 to 7.6) | 0.39 | 7.4 (6.5 to 8.6) | 6.8 (6.0 to 7.5) | 0.68 |
| International normalized ratioe | 1.0 (1.0 to 1.1) | 1.0 (1.0 to 1.0) | 0.23 | 1.0 (1.0 to 1.1) | 1.0 (1.0 to 1.0) | 0.36 |
| Platelet count, × 109/Le | 253 (210 to 297) | 240 (199 to 289) | 0.13 | 248 (208 to 292) | 243 (201 to 290) | 0.07 |
| HDL cholesterol, mg/dLe | 41 (35 to 49) | 43 (36 to 50) | −0.12 | 41 (35 to 49) | 43 (36 to 51) | −0.25 |
| LDL cholesterol, mg/dLe | 98 (77 to 123) | 111 (89 to 141) | −0.45 | 98 (77 to 123) | 114 (89 to 142) | −0.67 |
| Triglycerides, mg/dLe | 162 (119 to 225) | 165 (121 to 231) | 0.02 | 159 (118 to 228) | 167 (122 to 232) | 0.05 |
| Liver biopsy, No. (%) or % | ||||||
| Steatosis score | ||||||
| 1 | 263 (40.5) | 159 (31.3) | 0.19 | 38.7 | 33.3 | 0.14 |
| 2 | 253 (38.9) | 227 (44.7) | 38.1 | 44.1 | ||
| 3 | 134 (20.6) | 122 (24.0) | 23.2 | 22.6 | ||
| Lobular inflammation score | ||||||
| 1 | 325 (50.0) | 298 (58.7) | 0.20 | 47.3 | 61.6 | 0.31 |
| 2 | 303 (46.6) | 186 (36.6) | 48.6 | 34.5 | ||
| 3 | 22 (3.4) | 24 (4.7) | 4.0 | 3.9 | ||
| Hepatocyte ballooning score | ||||||
| 1 | 544 (83.7) | 351 (69.1) | 0.35 | 81.6 | 72.0 | 0.23 |
| 2 | 106 (16.3) | 157 (30.9) | 18.4 | 28.0 | ||
| Histological NAFLD activity scorej | ||||||
| 3 | 129 (19.8) | 85 (16.7) | 0.16 | 18.5 | 18.5 | 0c |
| 4 | 209 (32.2) | 150 (29.5) | 30.7 | 30.7 | ||
| 5 | 200 (30.8) | 140 (27.6) | 29.2 | 29.2 | ||
| 6 | 86 (13.2) | 102 (20.1) | 16.5 | 16.5 | ||
| 7 | 23 (3.5) | 29 (5.7) | 4.8 | 4.8 | ||
| 8 | 3 (0.46) | 2 (0.39) | 0.4 | 0.4 | ||
| Histological liver fibrosis stagek | ||||||
| 1 | 380 (58.5) | 226 (44.5) | 0.28 | 50.8 | 50.8 | 0c |
| 2 | 158 (24.3) | 160 (31.5) | 29.2 | 29.2 | ||
| 3 | 112 (17.2) | 122 (24.0) | 20.0 | 20.0 | ||
Abbreviations: BMI, body mass index; BP, blood pressure; CCI, Charlson Comorbidity Index; HDL, high-density lipoprotein; LDL, low-density lipoprotein; NAFLD, nonalcoholic fatty liver disease.
SI conversion factors: To convert bilirubin to μmol/L, multiply by 17.104; creatinine to μmol/L, multiply by 76.25; hemoglobin A1c to mmol/mol, subtract 2.152 from the percentage value and divide by 0.0915; HDL and LDL cholesterol to mmol/L, multiply by 0.0259; triglycerides to mmol/L, multiply by 0.0113.
After overlap weighting, a single individual no longer represents a single data entity and thus raw counts are not reported after overlap weighting.
Absolute value of the between-group difference in means or proportions (bariatric surgery − nonsurgical control) divided by the pooled SD.
Overlap weighting provided precise balance for these important variables.
Calculated as weight in kilograms divided by height in meters squared.
There were missing data for this variable. Missing values were handled with multiple imputation. For albumin, there were missing data for 82 patients; annual zip code income, 17 patients; bilirubin, 81 patients; creatinine, 85 patients; HDL cholesterol, 350 patients; hemoglobin A1c, 154 patients; international normalized ratio, 523 patients; LDL cholesterol, 365 patients; platelet count, 59 patients; systolic and diastolic BP, 31 patients; and triglycerides, 347 patients.
The diagnosis codes appear in eTable 3 in Supplement 2.
A method of predicting the risk of mortality based on the International Classification of Diseases diagnosis codes for 17 comorbidities. Presence of each comorbidity is awarded a point from 1 to 6. The final score is calculated by the summation of applicable points and scores range from 0 (no disease burden) to 29 (maximal disease burden).
The normal value range is 3.9 g/dL to 4.9 g/dL for albumin; 0.2 mg/dL to 1.3 mg/dL for bilirubin; 0.58 mg/dL to 0.96 mg/dL for creatinine; >39 mg/dL for HDL cholesterol; 4.3% to 5.6% for hemoglobin A1c; 0.9 to 1.3 for international normalized ratio; <100 mg/dL for LDL cholesterol; 150 to 400 × 109/L for platelet count; and <150 mg/dL for triglycerides.
Only measured in patients with type 2 diabetes at baseline.
Higher scores indicate more severe histological changes. Calculated based on the cumulative scores of liver steatosis (grade of 0 to 3), hepatocyte ballooning (grade of 0 to 2), and lobular inflammation (grade of 0 to 3).
Higher stages represent more severe fibrosis. Stage 0, no fibrosis; stage 1, perisinusoidal or periportal; stage 2, perisinusoidal and portal or periportal; stage 3, bridging fibrosis; and stage 4, cirrhosis.