Major lower extremity amputations (MLEAs) are understood to be well recorded in secondary care in England in the Hospital Episode Statistics (HES) database. It is unclear how well MLEAs are recorded in primary care databases.

This study compared MLEA event case ascertainment in Clinical Practice Research Datalink (CPRD) to that in HES.

MLEA events were ascertained in CPRD and in HES linkage between 1 January 2010 and 31 December 2019. The number of MLEA events and the number of patients with at least one MLEA in each database were recorded and compared. Individual events were matched between the databases using varying date-matching windows. Reasons for differences in case ascertainment were explored.

In total 23 262 patients had at least one MLEA record, 8716 (37.5%) had an MLEA record in HES only, 5393 (23.2%) in CPRD only and 9153 (39.4%) in both. Out of a total of 75 221 events, 13 071 (62.4%) were recorded in HES only and 44 151 (81.3%) in CPRD only. 7874 (37.6%) of HES events were recorded in CPRD and 10 125 (18.6%) of CPRD events were recorded in HES when using the maximum date matching window of 28 days plus the time between admission and procedure. The main reasons for differences in case ascertainment included, re-recordings and miscoding in CPRD.

Compared to HES, MLEAs are poorly recorded in CPRD predominantly due to re-recordings of events and miscoding procedures. CPRD data cannot solely be relied upon to ascertain cases of MLEA; however, HES linkage to CPRD may be useful to obtain medical history of diagnoses, medication and diagnostic tests.