Completeness and representativeness of small area socioeconomic data linked with the UK Clinical Practice Research Datalink (CPRD)

Abstract

Background: The Clinical Practice Research Datalink (CPRD) holds primary care electronic healthcare records for 25% of the UK population. CPRD data can be linked via practice postcode in the UK, and additionally via patient postcode in England, to area-level socioeconomic status (SES) data including the Index of Multiple Deprivation (IMD), the Carstairs Index and the Townsend Deprivation Index; as well as rural-urban classification (RUC). This study aims to describe the completeness and representativeness of CPRD-linked SES and RUC data.

Methods: Patients currently registered at general practices contributing data to the May 2021 snapshots of CPRD GOLD (n=445 587) and CPRD Aurum (n=13 278 825) were used to assess the completeness and representativeness of CPRD-linked SES and RUC data against the UK general population.

Results: All currently registered patients had complete SES and RUC data at practice level across the UK. Most English patients in CPRD GOLD (78%), CPRD Aurum (94%) and combined (93%) had SES and RUC data at patient level. Patient-level SES data in CPRD for England were comparable to England's general population (average IMD decile in CPRD 5.52±0.00 vs 5.50±0.02). CPRD UK practices were on average in more deprived areas than the UK general population (6.06±0.07 vs 5.50±0.02). A slightly higher proportion of CPRD patients and practices were from urban areas (85%) as compared with the UK general population (82%).

Conclusion: Completeness of CPRD-linked SES and RUC data is high. The CPRD populations were broadly representative of the general populations in the UK in terms of SES and RUC.

Keywords: biostatistics; epidemiology; public health; social class.

Figure 1

Availability of linked small area datasets in the Clinical Practice Research Datalink (CPRD) at the (top) patient level or (bottom) practice level, including the year of the dataset, and the comparability of measures between countries for each dataset. Linkages are available for both the CPRD GOLD and the CPRD Aurum databases.

Figure 2

Correlation between socioeconomic status (SES) rankings (A) within patients and (B) between patients and their practice. Correlations between the Index of Multiple Deprivation (IMD) Composite, Carstairs Index and Townsend Deprivation Index both within patients and between patients and their practice. Correlation for rural–urban classification (RUC) between patients and their practice. Correlations in the Clinical Practice Research Datalink (CPRD) acceptable patient population from England only (CPRD GOLD and CPRD Aurum, combined) in May 2021. NA, not applicable.

Figure 3

Proportion of patients with the same or different deprivation level as their practice per the (A) Index of Multiple Deprivation (IMD) Composite, (B) Carstairs Index and (C) Townsend Deprivation Index, or (D) rural–urban classification (RUC) in the Clinical Practice Research Datalink (CPRD) acceptable patient population from England only (CPRD GOLD and CPRD Aurum, combined) in May 2021. Colouring shows the level of agreement (%) between patient-level rank and practice-level rank.

Figure 4

Representativeness of practice-level socioeconomic status (SES) measures—Index of Multiple Deprivation (IMD) Composite, Carstairs Index and Townsend Deprivation Index—in the Clinical Practice Research Datalink (CPRD) (CPRD GOLD and CPRD Aurum, combined) in terms of average decile of deprivation ±SD for all currently contributing practices in (A) England, Great Britain and the UK and (B) Northern Ireland, Scotland, and Wales in May 2021. The Carstairs Index is not available for Northern Ireland or the UK.

Figure 5

(A) Representativeness of patient-level socioeconomic status (SES) measures—Indices of Multiple Deprivation (IMD) Composite, Carstairs Index and Townsend Deprivation Index—in the Clinical Practice Research Datalink (CPRD); CPRD GOLD and CPRD Aurum, individually and combined) in terms of average decile of deprivation ±SD for all acceptable, currently registered patients in England in May 2021. (B) Representativeness of patient-level rural–urban classification (RUC) in CPRD (CPRD GOLD and CPRD Aurum, individually and combined) in terms of proportion (%) rural and urban for all acceptable, currently registered patients in England in May 2021 compared with the national measure.