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Aims:

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.

Background:

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

Methods:

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.

Findings:

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.

Annual seasonal influenza vaccination is recommended for individuals at high risk of developing post-infection complications in many locations. However, reduced vaccine immunogenicity and effectiveness have been observed among repeat vaccinees in some influenza seasons. We investigated the impact of repeated influenza vaccination on relative vaccine effectiveness (VE) among individuals who were recommended for influenza vaccination in the United Kingdom with a retrospective cohort study using primary healthcare data from the Clinical Practice Research Datalink, a primary care database in the United Kingdom. Relative VE was estimated against general practitioner-diagnosed influenza-like illnesses (GP-ILI) and medically attended acute respiratory illnesses (MAARI) among participants who have been repeatedly vaccinated compared with first-time vaccinees using proportional hazards models. Relative VE against MAARI may be reduced for individuals above 65 years old who were vaccinated in the current and previous influenza seasons for some influenza seasons. However, these findings were not conclusive as we could not exclude the possibility of residual confounding in our dataset. The use of routinely collected data from electronic health records to examine the effects of repeated vaccination needs to be complemented with sufficient efforts to include negative control outcomes to rule out residual confounding.

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Are major lower extremity amputations well recorded in primary care electronic health records?: Insights from primary care electronic health records in England

The impact of repeated vaccination on relative influenza vaccine effectiveness among vaccinated adults in the United Kingdom

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Are major lower extremity amputations well recorded in primary care electronic health records?: Insights from primary care electronic health records in England

The impact of repeated vaccination on relative influenza vaccine effectiveness among vaccinated adults in the United Kingdom