Table 6.
Linear regression models to evaluate associations of lead dose biomarkers and uric acid levels with renal outcomes in 266 lead workers in the oldest tertile of age.
| Method 1 (lead biomarker models)
|
Method 2 (uric acid models)
|
Method 3 (combined models)
|
|||||||
|---|---|---|---|---|---|---|---|---|---|
| Independent variables | βcoefficient | SE β | p-Value | βcoefficient | SE β | p-Value | βcoefficient | SE β | p-Value |
| BUN (mg/dL) models | |||||||||
| Blood lead (μg/dL) | 0.0352 | 0.0183 | 0.05 | — | — | — | 0.0293 | 0.0185 | 0.11 |
| Uric acid (mg/dL) | — | — | — | 0.4663 | 0.2307 | 0.04 | 0.3963 | 0.2343 | 0.09 |
| Serum creatinine (mg/dL) models | |||||||||
| Blood lead (μg/dL) | 0.0016 | 0.0006 | < 0.01 | — | — | — | 0.0012 | 0.0006 | 0.03 |
| Uric acid (mg/dL) | — | — | — | 0.0245 | 0.0072 | < 0.01 | 0.0215 | 0.0073 | < 0.01 |
| Tibia lead (μg Pb/g bone mineral) | 0.0004 | 0.0002 | 0.03 | — | — | — | 0.0003 | 0.0002 | 0.06 |
| Uric acid (mg/dL) | — | — | — | 0.0246 | 0.0072 | < 0.01 | 0.0233 | 0.0072 | < 0.01 |
| Measured creatinine clearance (mL/min) models | |||||||||
| Blood lead (μg/dL) | 0.1187 | 0.1177 | 0.31 | — | — | — | 0.1697 | 0.1198 | 0.16 |
| Uric acid (mg/dL) | — | — | — | −2.4871 | 1.4456 | 0.09 | −2.9352 | 1.4769 | 0.05 |
| Calculated creatinine clearance (mL/min) models | |||||||||
| Blood lead (μg/dL) | −0.1221 | 0.0594 | 0.04 | — | — | — | −0.0950 | 0.0600 | 0.11 |
| Uric acid (mg/dL) | — | — | — | −2.0384 | 0.7487 | < 0.01 | −1.8095 | 0.7604 | 0.02 |
| ln NAG [ln (μmol/hr/g creatinine)] models | |||||||||
| Blood lead (μg/dL) | 0.0089 | 0.0028 | < 0.01 | — | — | — | 0.0092 | 0.0028 | < 0.01 |
| Uric acid (mg/dL) | — | — | — | −0.0115 | 0.0364 | 0.76 | −0.0289 | 0.0361 | 0.42 |
| Tibia lead (μg Pb/g bone mineral) | 0.0023 | 0.0008 | < 0.01 | — | — | — | 0.0023 | 0.0008 | < 0.01 |
| Uric acid (mg/dL) | — | — | — | −0.0070 | 0.0366 | 0.85 | −0.0094 | 0.036 | 0.80 |
| DMSA-chelatable lead (mg Pb/g creatinine) | 0.1931 | 0.0511 | < 0.01 | — | — | — | 0.1944 | 0.0512 | < 0.01 |
| Uric acid (mg/dL) | — | — | — | −0.0182 | 0.0373 | 0.63 | −0.0235 | 0.0363 | 0.52 |
BUN, serum creatinine, measured creatinine clearance, and calculated creatinine clearance models were also adjusted for age, sex, BMI, current/former worker status, and hypertension. NAG and RBP models were adjusted for age, sex, BMI, systolic blood pressure, current/former worker status, alcohol ingestion, and diabetes. Only models in which p ≤0.05 for the lead variable without uric acid adjustment are shown, with the exception of the measured creatinine clearance model; this model is included because the p-value for the β-coefficient of the uric acid variable decreased to ≤0.05 after adjustment for blood lead.