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HbA1c

Description

Identifying and cleaning HbA1c values iN EHR data.

Rules

To note: steps 1-4 below should be carried out in this order to produce a standardised end reult:

  1. Convert all values to mmol/mol; where unit codes are not available we assume values <=20 are in % and require conversion.
  2. Remove values less than 20 or greater than 195 mmol/mol as these are implausible.
  3. Apply additional cleaning rules based on unit codes where available.

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

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

  6. In patients with diabetes, elevated HbA1c values (>=48 mmol/mol; based on clean values aggregated by patient identifier and date) are used in the algorithm to define diagnosis date - see conditions/diabetes.

Origins

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

Data

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