Table 4 Linear regression modelling of effect modification by ALAD genotypes on some renal parameters and blood lead levels.
| β coefficient | SE β | p value | |
|---|---|---|---|
| Urinary β2 microglobulin (log_Uβ2m) | |||
| R2 = 0.326 | |||
| Intercept | −0.96 | 0.17 | <0.001 |
| ALADg | −0.60 | 0.24 | 0.014 |
| Log_PbB(μg/dl) | 0.11 | 0.08 | 0.181 |
| Log_PbB*ALADg | 0.47 | 0.20 | 0.020 |
| Urinary α1 microglobulin (log_Uα1m) | |||
| R2 = 0.160 | |||
| Intercept | 0.55 | 0.12 | <0.001 |
| ALADg | −0.35 | 0.06 | 0.040 |
| Log_PbB(μg/dl) | 0.07 | 0.06 | 0.208 |
| Log_PbB*ALADg | 0.26 | 0.14 | 0.068 |
| Urinary N‐acetyl‐glucosaminidase (log_UNAG) | |||
| R2 = 0.138 | |||
| Intercept | −0.23 | 0.14 | 0.094 |
| ALADg | −0.37 | 0.20 | 0.065 |
| Log_PbB (μg/dl) | 0.30 | 0.07 | <0.001 |
| Log_PbB*ALADg | 0.29 | 0.17 | 0.083 |
| Urinary aminolevulinic acid (log_ALAU) | |||
| R2 = 0.215 | |||
| Intercept | −0.63 | 0.10 | <0.001 |
| ALADg | −0.05 | 0.14 | 0.731 |
| Log_PbB (μg/dl) | 0.40 | 0.05 | <0.001 |
| Log_PbB*ALADg | −0.02 | 0.12 | 0.870 |
| Urinary retinol binding protein (log_URBP) | |||
| R2 = 0.387 | |||
| Intercept | −0.78 | 0.15 | <0.001 |
| ALADg | −0.40 | 0.21 | 0.058 |
| Log_PbB (μg/dl) | −0.03 | 0.07 | 0.685 |
| Log_PbB*ALADg | 0.26 | 0.18 | 0.132 |
| Urinary albumin (log_Ualb) | |||
| R2 = 0.09 | |||
| Intercept | 0.62 | 0.14 | <0.001 |
| ALADg | −0.42 | 0.20 | 0.035 |
| Log_PbB (μg/dl) | −0.04 | 0.07 | 0.541 |
| Log_PbB*ALADg | 0.30 | 0.16 | 0.068 |
The model adjusts for age, gender, race, and exposure duration. ALADg refers to the ALAD genotypes. ALADg has two categories, ALAD1‐1 = 0, ALAD1‐2/2‐2 = 1.
The reference group is ALAD1‐1; the β coefficient of log_PbB is the slope for the association between PbB and renal parameters in participants with this genotype. The corresponding slope in participants with ALAD1‐2/2‐2 is the sum of the beta coefficient of log_PbB and that of log_PbB*ALADg in each model. (i.e. in the Uα1m model, the β coefficient of log_PbB for ALAD1‐1 group is 0.07, the corresponding β for ALAD1‐2/2‐2 is 0.33 = 0.07+0.26). P values for the log_PbB*ALADg reflect the statistical significance of the difference between the slopes of the regression line for ALAD1‐1 participants and for ALAD1‐2/2‐2 participants.