Metadata

Name White Blood Cells
Type Biomarker
Group Biomarker
Data Sources
Clinical Terminologies Read Version 2
Codelists
Valid Event Data Range 01/01/1999 - 01/07/2016
Sex Female
Male
Authors Shah A
Agreement Date 23 Nov 2012
Version (UUID) Revision 1 (m9LJwQVE3LVudvQ5bCu6MZ)

Primary Care

In the Clinical Practice Research Datalink (CPRD, primary care data) we extracted white blood cell measurements using the structured data component of the test CPRD table (entity type 207) combined with a list of Read terms (see below). The value was extracted from the data2 field where the units data3 field were set as 37 [109/L], 153 [109], 17 [/L]. We filtered any values less than 50 10^9/L.

Read code Read term CALIBER category
42H..00 Total white cell count Total blood white cell count
42H..11 White blood count Total blood white cell count
42H..12 White cell count Total blood white cell count
42H1.00 White cell count normal Total blood white cell count
42H2.00 Leucopenia - low white count Total blood white cell count
42H2.11 Leucopenia Total blood white cell count
42H3.00 Leucocytosis -high white count Total blood white cell count
42H3.11 Leucocytosis Total blood white cell count
42H5.00 White cell count abnormal Total blood white cell count
42H7.00 Total white blood count Total blood white cell count
42H8.00 Total WBC (IMM) Total blood white cell count
42HZ.00 Total white cell count NOS Total blood white cell count
D400A00 Leucopenia Total blood white cell count
D40y.11 Leucocytosis Total blood white cell count
D40y.12 Leukocytosis Total blood white cell count
D40yz11 Leucocytosis Total blood white cell count

Implementation

Total white cell counts can be affected by many factors such as infections, autoimmune diseases, medication and haematological conditions. Similar to our recent study on eosinophil counts,1 we sought to differentiate between a patient’s long-term ‘stable’ total white cell count and results obtained when the patient had an ‘acute’ condition which may alter leukocyte counts. We used other information in the electronic health record (prescriptions, diagnoses, symptoms, hospitalisations) to assess whether the patient was clinically ‘acute’ or ‘stable’ at the time of the blood test, adapting a set of criteria proposed by the eMERGE consortium (electronic Medical Records and Genomics)2 for studying genetic determinants of the stable leukocyte counts: in hospital on the date of blood test, vaccination in the previous 7 days, anaemia diagnosis within the previous 30 days, symptoms or diagnosis of infection within the previous 30 days, prior diagnosis of myelodysplastic syndrome, prior diagnosis of haemoglobinopathy, cancer chemotherapy or G-CSF within 6 months before index date, the use of drugs affecting the immune system such as methotrexate or steroids within the previous 3 months, prior diagnosis of HIV infection, prior splenectomy or prior dialysis.