**Definition** | Estimated glomerular filtration rate using CKD-EPI formula, using serum creatinine in micromol/L.
Reference: Levey AS et al. A New Equation to Estimate Glomerular Filtration Rate, Ann Intern Med. 2009;150:604-612. http://annals.org/article.aspx?articleid=744469
Note: We do not know if creatinine measurements in CPRD are calibrated to IDMS. Therefore we multiply the raw creatinine by 0.95 to obtain conservative values for perhaps uncalibrated creatinine. We also multiply by 0.011312 to convert from micromol/L to mg/dL. |

**Implementation** | egfr_ckdepi = 141 * min(crea_gprd * 0.010746 / K, 1)^alpha
* max(crea_gprd * 0.010746 / K, 1)^-1.209
* 0.993^age * 1.018 [if female] * 1.159 [if black]
where:
alpha = -0.329 for females, -0.411 for males
K = 0.7 for females, 0.9 for males |