Pulmonary embolism (P.E.) in Primary Care
How often should a full-time GP see (on average) a PE in primary care?
About 1 case per year of practice (1,2)
Caveats: This assumes a patient-FTE ratio of 1,268:1 (average for Cornwall(3)). To apply it to part-time primary care working, divide by proportion of FTE hours worked. BUT REMEMBER, its an average presentation rate - seeing one today doesn't mean your next will necessarily be in a years time. It also comes from populations not necessarily representative of the local population (as we don't yet have the data), and in one study comes from measures of confirmed cases, affected by testing protocols. But it might serve as a rough 'finger in the air' estimation of the incidence of PE presentations in primary care.
1. Oger E. Incidence of venous thromboembolism: a community-based study in Western France. Thromb Haemost 2000;83:657–6
2. Stein PD, Henry JW. Prevalence of acute pulmonary embolism among patients in a general hospital and at autopsy. Chest. 1995;108:978-981
Is there a tool to rule out PE in the low risk patient?
The PERC rule allows an estimation of the unlikely incidence (<2%) of PE in the low risk patient without serum testing or further work up. In it's original study, it was validated against clinical gestalt of low risk - that is, for use in those patients which you feel a PE is unlikely. In a bid to clarify how unlikely (the pretest probability), the PERC rule has later been used in conjunction with Wells scoring for those patients the Wells score suggests are <15% likely to have PE. There is some duplication of criteria making this use arguable. Regardless, IF YOU THINK THEY LIKELY DON'T HAVE A PE, and they are PERC score 0, the patient's likelihood of having a PE is <2%. It has been suggested that at this risk level, no further acute work up for PE is required (but adequate safetynetting should be given, as well as differentials pursued).
If PE is suspected and they score 1 or more on PERC, please discuss with the AGP service.
PE in Covid
Here is the British Thoracic Guidance to VTE in Covid. It mostly relates to VTE during concomitant Covid infection in those severely symptomatic likely hospitalised patients - this is where we have most of the data - who are around 6 times more likely to have some form of venous thrombotic disease. The difficulty is in primary care we are seeing:
- milder cases of Covid
- prolonged symptomatic recovery periods
Little is known about the latter, but in the absence of evidence some assumptions can be made.
1) Other viral pneumonias can produce recovery periods of 6-8 weeks before return to baseline lung function. It is likely the pneumonitis seen with Covid has similar recovery timescales.
2) If there is an increased risk of VTE in severely affected patients, then it stands there is an increased (although uncertain how much) risk of VTE in the community-managed Covid patient
3) D-dimer is an independent predictor of outcome severity in Covid-19. As an acute phase reactant it increases non-specifically with the disease. This implies its ability to rule-out VTE (when it's negative) remains, but there may be more false positives for VTE around the acute infection
4) So we remain with our diagnostic protocol for PE. As always, in terms of finding or ruling out PE, the test is most reliable when your clinical gestalt/feel is clear...trust your clinician 'gut'.