MDRD eGFR Calculator (4-Variable)
MDRD eGFR Calculator (4-Variable)
The legacy MDRD Study equation, still quoted in older records, drug labels and trial criteria.
MDRD eGFR (4-Variable)
Legacy equationMale, age 62, creatinine 1.3 mg/dL, no race coefficient
Formula
- 175
- the IDMS-traceable constant; the original 1999 publication used 186 for non-standardised assays
- Scr
- serum creatinine in mg/dL
- 1.212
- the historical race coefficient, now widely removed — see below
Worked example
Male, age 62, creatinine 1.3 mg/dL, no race coefficient
175 × 1.3^−1.154 × 62^−0.203 = 56 mL/min/1.73 m²
CKD-EPI 2021 gives 62 for the same inputs — MDRD reads about 10% lower here
MDRD compared with CKD-EPI
| MDRD | CKD-EPI 2021 | |
|---|---|---|
| Derived in | Patients with known CKD | Pooled CKD and general population |
| Accuracy above 60 | Poor — systematically underestimates | Good |
| Accuracy below 60 | Reasonable | Reasonable |
| Race term | 1.212, historical | None |
| Current status | Legacy | Recommended |
Why MDRD is still here
The MDRD Study equation was derived in 1999 from patients with established chronic kidney disease, and for two decades it was what most laboratories reported. Its defining weakness follows directly from that derivation cohort: it was never fitted on people with normal kidney function, and it systematically underestimates GFR above about 60 mL/min/1.73 m². That produced a great deal of false-positive CKD labelling in healthy adults.
CKD-EPI corrected this and has replaced it in guidelines and in most laboratories. MDRD nevertheless persists in three places worth knowing about. Older records report it, so comparing a current eGFR against a value from ten years ago may be comparing two different equations rather than measuring a change. Many drug labels and clinical trial eligibility criteria were written using it. And some laboratories still report it alongside CKD-EPI.
The race coefficient of 1.212 has been removed by most institutions for the same reasons it was removed from CKD-EPI. This calculator defaults to not applying it, with the option retained only so historical values can be reproduced when auditing an old record.
Frequently asked questions
Should I use MDRD or CKD-EPI?
CKD-EPI 2021 for any current clinical decision. MDRD is useful only for reproducing a historical value or meeting a trial or drug-label criterion that specifies it.
Why does MDRD give a lower eGFR than CKD-EPI?
It was derived only in patients with established kidney disease, so it underestimates GFR in people with better function — the difference is largest above 60 mL/min/1.73 m².
What is the difference between the 175 and 186 versions?
186 was the original constant for non-standardised creatinine assays. 175 is the version for IDMS-traceable assays, which is what all modern laboratories use.
Should the race coefficient be applied?
No, not for clinical use. It has been removed by most institutions for the same reasons it was removed from CKD-EPI. The option here exists only to reproduce historical values.
Related calculators
References
- Levey AS et al. A more accurate method to estimate glomerular filtration rate from serum creatinine. Ann Intern Med. 1999;130(6):461–70.
- Levey AS et al. Expressing the MDRD study equation for estimating GFR with IDMS traceable results. J Am Soc Nephrol. 2007;18:2749.