106737864
Pseudocode to select T2DM (type 2 diabetes mellitus) cases & controls:
Data to retrieve from the EMR by patient (specific codes and medications listed in the phenotype
definition document):

Number of dates with T2DM ICD-9 codes in patient’s encounters, problem list, and medical
history, by these diagnostic sources

Number of dates with T1DM ICD-9 codes in patient’s encounters, problem list, and medical
history, by these diagnostic sources

Insulin, insulin supply, & Symlin prescription dates (at least the last date)

T2DM medications prescription dates (at least the last date)

Fasting blood glucose lab values (at least the maximum)

Random blood glucose lab values (at least the maximum)

HBA1c lab values (at least the maximum)
For selecting controls also need this data:

diabetes family history

Related diabetes conditions’ ICD-9 codes
If you have any questions about this pseudocode, please contact:
Jennifer S. Allen
NUgene Informatics Lead
312-695-0712
jennifer-allen@northwestern.edu
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106737864
Flowchart for selecting cases: Algorithm for the Identification of Subjects with Type 2 Diabetes:
Patient Population
T2DM ICD9 code(s)
No T2DM and T1DM ICD9 codes
1)
2)
Treated with T2DM
medication
Treated with insulin
medication
No DM medication
but abnormal lab*
(iii)
Never on T2DM
medication
Treated with T2DM medication &
have an abnormal lab*
(iv)
On T2DM
medication in past
(i)
T1DM ICD9
code(s) & <2
diagnosis^ date
Type 2 Diabetes Cases
No T1DM ICD9
code & ≥2
diagnoses^ dates
(ii)
* Random glucose > 200mg/dl, Fasting glucose > 125 mg/dl, or hemoglobin A1c ≥6.5%.
^ Encounter or problem list diagnoses only (all other diagnoses in this chart could also include diagnoses in the medical history)
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(i)
106737864
From the EMR data, use the following logic to determine if a patient could be a case:
(Numbering below matches the numbers in the boxes in the above diagram)
IF a patient with at least 2 clinic (face-to-face outpatient clinic) visits:
1) is diagnosed with T2DM in an encounter, problem list, or in the medical history, AND :
i.
is currently prescribed only insulin or Symlin or insulin supplies (T1DM meds)
AND has been prescribed T2DM medication in the past
OR:
ii.
is currently prescribed only insulin or Symlin or insulin supplies (T1DM meds)
AND does not have any T1DM diagnoses
AND has been diagnosed on >= 2 dates with T2DM in encounter(s) or problem list
OR:
iii.
is prescribed T2DM medication;
and if also prescribed insulin or Symlin, prescribed at same time or before T2DM
medication prescribed
OR:
iv.
NOT prescribed any (T1 or T2) DM medication
AND has an abnormal lab*
OR:
2) is NOT diagnosed with T2DM NOR T1DM
i.
AND is prescribed T2DM medication
AND has an abnormal lab*
THEN the patient has T2DM.
* abnormal lab:= random (not a glucose tolerance test nor part of a pregnancy screen) blood glucose
level >200 mg/dL OR fasting blood glucose level > 125 mg/dL OR (glyco)hemoglobin A1c >= 6.5%
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106737864
Flowchart for selecting controls:
From the EMR data, use the following logic to determine if a patient could be a control:
IF a patient has at least 2 clinic (face-to-face outpatient clinic) visits**:
AND is NOT diagnosed with diabetes or related conditions
AND has NOT been prescribed insulin or Symlin or T2DM medications or any diabetic supplies
AND has a glucose lab** AND it is < 110 mg/dL
AND IF the patient has an HBA1c lab, it is < 6.0%
AND IF the patient has family history data, there is no history of diabetes
THEN the patient can be a T2DM CONTROL.
**These criteria help to ensure that we are only using patients as controls if they have enough data in
their EMR in order for us to safely assume they meet the control criteria.
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