The effect of lockdown and media coverage following vaccine rollout on Deep Vein Thrombosis ( DVT ) clinic activity during the first year of the COVID -19 pandemic-a single-centre experience

ABSTRACT

An explosion of research has occurred since the advent of the COVID-19 pandemic relating to its effect on the NHS, health consciousness and vaccine side effects, such as vaccine-induced thrombocytopenia and thrombosis (VITT). This project sought to establish the effects of the UK's national lockdowns and media coverage of VITT on the rate of referrals and outcomes of DVT clinic appointments at our hospital. There was a suspicion among nurses running the DVT clinic that referrals were lower, but rates of positive scans higher, during the first national lockdown and that the reverse was true following media reporting of the first cases of VITT, with large numbers of patients testing negative for DVT. We report the findings of a retrospective, observational case-control study of 3550 patients presenting to Norfolk and Norwich University Hospital outpatient DVT clinic from any referral source (usually GP or A + E) between 2/3/2020 and 10/5/2021. Data from 2015 to 2019 were also obtained, providing 5-year averages for comparison. Outcomes were classified as positive (for DVT), negative (including those where Doppler ultrasound scan was not indicated due to low Wells score and negative D-dimer) and DNA (did not attend). Chi-squared (χ2 ) analyses were undertaken to determine heterogeneity of weekly referrals during specific periods of the pandemic. With 2 degrees of freedom (2df), a χ2 result above 5.9 suggests heterogeneity. T -tests were run to compare the outcomes driving the χ2 results with the data from the preceding 5 years. Compared to the non-lockdown period, there was a significant reduction in the number of referrals seen during the dates of the 1st national lockdown (χ2 = 20.01, 2df, p = <0.01). This was primarily due to a reduction in the number of patients subsequently found to be negative for DVT (31.0 vs. 45.4, p = <0.01). The difference was less marked and did not reach statistical significance during the 2nd and 3rd lockdowns. A significant increase in total weekly referrals was observed during the period immediately following media reporting of the first cases of VITT related to the AstraZenaca COVID-19 vaccine (55.1 vs. 73.1, p = <0.01). This was driven by an increase in patients subsequently found to be negative for DVT (39.2 vs. 57.2 p = <0.01). The weekly number of positive patients during this time was not significantly higher than the preceding 5-year average for the same dates (9.7 vs. 10.2, p = 0.30). Comparison with 5-year averages confirmed that the pattern seen in different parts of the pandemic year described above did not follow the usual pattern of referrals across the year. Finally, throughout the observed period, there was a below average rate of DNA outcomes when compared to the preceding 5-year average. These findings suggest several phenomena unique to the COVID-19 pandemic. First, measures to prevent the spread of COVID-19 were associated with fewer patients without DVT being referred to the DVT clinic. Second, media reporting of VITT was associated with a higher rate of referral of patients without a DVT to the DVT clinic without any change in the number of positive patients compared to the preceding 5 years. Third, during the COVD-19 pandemic, there were fewer patients failing to attend their clinic appointment, which we hypothesise is as a result of increased awareness of the need not to waste NHS resources..