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eGFR (estimated glomerular filtration rate)

Description

Defining and cleaning eGFR (estimated glomerular filtration rate) values in EHR data.

Rules

  • We recommend using cleaned serum creatinine values, age when value was measured and sex to calculate eGFR as per the CKD-EPI Creatinine Equation 2021 (ethnicity is not used in this equation). Using recorded eGFR values can lead to discrepancies where different equations have been used.

  • Cleaning serum creatinine values (to note: steps 1-3 below should be carried out in this order to produce a standardised end result):

  • Remove values less than 20 and greater than 2500 μmol/L as these are implausible.

  • Apply additional cleaning rules based on unit codes where available.

  • If multiple values recorded on the same day for a patient, we take the mean.

  • Check to make sure the date is within the range expected given the data source and patient DOB and death dates.

  • eGFR values can be used to infer CKD stage (see our previous work in CPRD)

Origins

  • The origin of the SNOMED codelist was the Pathology Bounded Code List (PBCL).

Data

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