Hazard group categorisation of COVID-19

In the UK, pathogens are categorised according to their risk to humans by the Advisory Committee on Dangerous Pathogens (ACDP) within the Health and Safety Executive.7ACDP guidance is largely aimed towards staff in clinical and research-related microbiology laboratories, however given the potential risk to the health of mortuary staff, autopsy practice has been adapted to reflect the risk of transmission of infectious pathogens during and after the postmortem examination.8These hazard groups (HG1–4) are assigned according to the risk of human infection, the likelihood spread and access to treatment or prophylaxis (seetable 1). Control of substances hazardous to health (COSHH) defines four containment levels for working with these, which correspond directly to the organism’s hazard group (ie, containment level 3 should be used for hazard group 3 organisms).

The SARS-related and MERS-related coronaviruses are both considered HG3 pathogens, while most otherCoronavirinaeare HG2.7SARS-CoV-2 has recently been categorised as a HG3 organism.4 7 9Other viruses within HG3 include rabies, poliovirus, dengue virus, hepatitis virus B, C, D and E, and HIV 1 and 2 among others.4Certain HG3 organisms (eg, hepatitis B, C, D and E virus) may be used at containment conditions less than those outlined by COSHH for HG3 organisms; however, SARS-CoV-2 is not on this list.7Once appropriate precautions are in place, the risk to mortuary workers dealing with these HG3 organisms are slight, and a well-staffed mortuary with experienced personnel should be capable of handling cases with any of these HG3 pathogens.

Risk reduction during postmortem examination in HG3 organisms

In general, conducting an autopsy on a patient with a suspected HG3 organisms requires four areas of attention: risk assessment, understanding of the pathology that may be found, universal standard precautions and any standard operating procedures for specific HG3 pathogens. The effective utilisation of universal precautions mitigates against inaccurate or incomplete information used in the risk assessment on an individual case basis.

Mortuary workers performing autopsies have a duty outlined by COSHH to perform risk assessments in every postmortem examination for the safety of themselves and their colleagues. Before the time of the autopsy, this may include a review of the clinical history on the consent form or coroner request form, information attained from the patient’s doctors, laboratory records and hospital infection control and external examination findings.

It must be stressed at this point that if the death is considered to be due to a confirmed COVID-19 infection, an autopsy is unlikely to be necessary and a Medical Certificate of Cause of Death should be given. However, if the infection is involved in a forensic case, then legal duty impels the proper performance of a full appropriate autopsy. The issue of whether a person dies with or from COVID-19 infection may not always be straightforward, and ongoing epidemiology and available investigation data may shed light on this.

Pathological findings in COVID-19

Information regarding the pathological findings in COVID-19 is limited, although several case reports have been published in recent weeks.10 11

Clinical features: Public Health England (PHE) has outlined criteria to assess possibility of COVID-19 infection in patients.12These criteria are the same when the patient is deceased with the exception that the timelines given in the guidance refer to the time prior death or onset of relevant symptoms before death where known.

If it is considered that COVID-19 may have been related to death by these criteria, the choice of either to perform a full postmortem or an examination is limited only to retrieving the samples required to verify COVID-19 infection. This decision must be made according to the individual case and should include the requirements of the coroner or any pertinent individuals. A staged postmortem may also be considered. This involves taking only diagnostic samples initially and later considering or a more complete autopsy after the results of these diagnostic tests are available. This staged technique is recommended if possible.

Macroscopic features: the macroscopic features of COVID-19 are likely to be in the chest and may include pleurisy, pericarditis, lung consolidation and pulmonary oedema. Lung weight may be increased above normal. It should be noted a secondary infection may be superimposed on the viral infection that can lead to purulent inflammation more typical of bacterial infection.4

Microscopic findings:a recent article described the early histopathological features in COVID-19 in two patients who underwent surgical resections for lung adenocarcinoma but were later discovered to have had COVID-19 at the time of the operation.11The findings were non-specific and included oedema, pneumocyte hyperplasia, focal inflammation and multinucleated giant cell formation while no hyaline membranes were seen. Given that these patients were asymptomatic with respect to COVID-19 at the time of the operation, these are likely to reflect only early changes of acute lung injury in the infection.11In another case, a 50-year-old man died from severe COVID-19 infection and more marked histopathological findings were noted.10Samples were taken by postmortem biopsy, and a description of the gross postmortem findings is not given, although multiple ground glass opacities were noted on chest X-ray. The microscopic findings included diffuse alveolar damage with exudates.10The inflammation was predominantly lymphocytic, and multinucleated giant cells were seen alongside large atypical pneumocytes, although no definitive viral inclusions were noted. Microvesicular steatosis with mild inflammation was noted in the liver, although it was unclear whether this was related to the virus or iatrogenic. The features are very similar to those seen in SARS and MERS-coronavirus infections.13 14

Mortuary factors

Adequate ventilation is need where HG3 autopsies are being performed with enough separation from the rest of the mortuary. Either whole room ventilation or down-drafts at the work stations are acceptable.15Any electric bone saws used should have a vacuum that isolates aerosolised particles. It is preferable to have an isolated high-risk facility for performing HG3 autopsies, although this is not compulsory.8All essential equipment should be brought at the start of the postmortem examination (eg, sample receptacles, culture bottles and so on) to eliminate the need to leave and re-enter the workspace. Further information may be found in the appropriate National Health Service guidance documents.16

The team available for these high-risk, postmortem examinations best includes the pathologist, the anatomic pathology technician (APT) and a third circulator. The presence of a circulator is beneficial but not essential.8Suitably experienced autopsy pathology trainees (as assessed by senior staff) may be involved in HG3 autopsies with adequate supervision. No specific infection risk to pregnant trainees has been identified; however, they may decide not to undertake autopsy work, and this should be discussed with the deanery.