Table 2.
Threshold Effect Analysis of Sensitivity to Thyroid Hormone Indices on DR Using the Two-Piecewise Linear Regression Model
| Incident DR | Crude (OR, 95% CI, P) | Adjusted (OR, 95% CI, P) |
|---|---|---|
| Exposure TSHI | ||
| Fitting model by standard linear regression | 0.86 (0.61, 1.21) 0.39 | 1.20 (0.79, 1.83) 0.40 |
| Fitting model by two-piecewise linear regression | ||
| Inflection point of thyroid hormone Index | 3.28 | 3.54 |
| < Inflection point | 1.22 (0.77, 1.92) 0.40 | 1.45 (0.91, 2.31) 0.12 |
| > Inflection point | 0.17 (0.04, 0.73) 0.02 | 0.06 (0.00, 1.64) 0.10 |
| Log likelihood ratio | 0.017 | 0.008 |
| Exposure TT4RI | ||
| Fitting model by standard linear regression | 1.00 (0.99, 1.01) 0.98 | 1.01 (0.99, 1.02) 0.47 |
| Fitting model by two-piecewise linear regression | ||
| Inflection point of thyroid hormone Index | 11.69 | 11.67 |
| < Inflection point | 1.25 (0.89, 1.75) 0.19 | 1.34 (0.95, 1.89) 0.10 |
| > Inflection point | 1.00 (0.98, 1.01) 0.66 | 1.00 (0.99, 1.02) 0.88 |
| Log likelihood ratio | 0.155 | 0.092 |
| Exposure TFQI | ||
| Fitting model by standard linear regression | 0.70 (0.42, 1.18) 0.18 | 1.41 (0.69, 2.91) 0.35 |
| Fitting model by two-piecewise linear regression | ||
| Inflection point of thyroid hormone Index | 0.18 | 0.23 |
| < Inflection point | 1.34 (0.62, 2.90) 0.45 | 3.19 (1.24, 8.17) 0.02 |
| > Inflection point | 0.13 (0.02, 0.66) 0.01 | 0.11 (0.01, 0.93) 0.04 |
| Log likelihood ratio | 0.022 | <0.001 |
Notes: Crude model was adjust for: None Adjusted model was adjust for: Sex; Age; BMI; Duration of diabetes; HbA1c; HDL-C; FT3; FT4. P value < 0.05 was considered significant.
Abbreviations: OR Odds ratios, CI Confidence, Ref Reference; BMI, body mass index; HDL-C, high-density lipoprotein cholesterol; HbA1c, glycated hemoglobin; FT3, free triiodothyronine; FT4, free thyroxine; TSHI, TSH Index; TT4RI, TSH T4 resistance index; TFQI, Thyroid Feedback Quantile-based Index; DR, diabetic retinopathy.