Autopsy findings of COVID-19 in children: a systematic review and meta-analysis
SARS-CoV-1 caused severe acute respiratory syndrome (SARS) in 2002, MERS-related coronavirus (MERS-CoV) caused Middle East respiratory syndrome (MERS) in 2012, and now SARS-CoV-2 is causing COVID-19 disease since December 2019 that started from Wuhan city of China . This has affected most of the countries in the world . SARS-CoV-2 is an RNA virus and belongs to a family of beta coronaviruses such as SARS-CoV-1 and MERS-CoV . There are minor differences in the spike protein of SARS-CoV-2, which increases the transmission rate of this virus . The SARS-CoV-2 has affected all age groups but caused severe disease in persons with comorbidity . Clinical features of SARAS-CoV-2 range from mild respiratory symptoms to severe and fatal outcomes, including acute respiratory distress syndrome, multiorgan failure, and death . COVID-19 is associated with many complications like cardiovascular, including thrombosis and neurological manifestations . To understand COVID-19-related clinical manifestations, complications, and pathogenesis, it is required to investigate cellular targets of SARS-CoV-2 tropism, replication, and mechanism of viral dissemination . Autopsy studies may provide deeper insight into the underlying pathophysiology and pathogenesis of SARS-CoV-2 . But there are a limited number of autopsies for evaluating COVID-19-related pathogenesis and pathophysiology, especially in children. Restricted autopsies may be due to the recommendations to suspend post-mortems on patients with suspected/confirmed COVID-19 infection . Performing the autopsy of COVID-19 patients is very risky due to its highly contagious tissue material, and it requires an autopsy facility with appropriate biosafety measurements . There is a need to review the autopsy findings of COVID-19 to understand the COVID-related pathology in children. This systematic review aims to describe the autopsy findings in children due to COVID-19. 

It is a systematic review where we included studies where autopsies were performed in COVID-19-positive children who died. We searched PubMed (inception to 30th June 2021), EMBASE (inception to 30th June 2021), Google Scholar (inception to 30th June 2021), and Cochrane Database Reviews (30th June 2021). Search strategy for PubMed included “Autopsy in children COVID” OR “Autopsy COVID-19 children”. We searched EMBASE with keywords/exp “Autopsy COVID-19 children” AND “Autopsy COVID-19 Child”. The keywords for Google Scholar were “Autopsy COVID-19 children”, and for Cochrane Database Reviews, were “Autopsy COVID-19 children”. References of included studies were hand searched for additional studies. The authors initially selected studies through title and abstract and reviewed the full text if required. We extracted data from included studies in a pre-defined form. We used the Appraisal tool for Cross-Sectional Studies (AXIS ) to assess the methodological quality of included studies. Inclusion criteria The studies performed an autopsy on children (< 18 years) who were positive for COVID-19. We also included the studies that reported autopsy of children and adults and collected data for paediatric (< 18 years) patients from such studies. Exclusion criteria Randomised controlled trial (RCT) studies and an autopsy performed only on adult patients. Statistical methods We presented the continuous outcome data as mean ± SD and categorical data as percentages. We used STATA 12 for descriptive statistics. Meta‑analysis was performed using Cochrane RevMan 5.1. Meta‑analysis was performed only on studies of similar design and outcome measures. 

The studies performed an autopsy on children (< 18 years) who were positive for COVID-19. We also included the studies that reported autopsy of children and adults and collected data for paediatric (< 18 years) patients from such studies. 

Randomised controlled trial (RCT) studies and an autopsy performed only on adult patients. 

We presented the continuous outcome data as mean ± SD and categorical data as percentages. We used STATA 12 for descriptive statistics. Meta‑analysis was performed using Cochrane RevMan 5.1. Meta‑analysis was performed only on studies of similar design and outcome measures. 

The study selection flow diagram is shown in Fig. . By electronic database search, we found a total of 8564 records. After excluding duplicates and irrelevant studies by screening titles and abstracts, 42 potentially eligible studies were identified to review the full text (Fig. ). After reviewing full texts, 31 articles were further excluded, and 11 studies were included for qualitative synthesis and meta-analysis (Fig. ). There were 26 patients in the included studies. The critical appraisal of included studies is shown in Table . Autopsy procedure In the COVID-19 pandemic, there are some recommendations for autopsy performance. There should be at least a biosafety level-2 autopsy facility . In this pandemic, a complete autopsy (ideal) may not be possible because SARS-CoV-2 is highly contagious to autopsy staff; there are alternative autopsy methods like in situ sampling or minimally invasive techniques of puncture/core biopsy autopsies . This systematic review found that three studies partially performed the complete autopsy, and eight partially performed autopsies (Table ). Table shows the clinical parameters of included patients. The mean age of patients was 5.9 ± 5.7 years who got infected by COVID-19. The review had 15 (57.7%) girls and 11 (42.3%) boys, with a ratio of 1.36. The mean total duration of the disease (10 studies) was 12.6 ± 10.7 days and the mean duration of hospital stay (8 studies) was 7.8 ± 10.6 days. Children’s mean body mass index (three studies) was 3.8 ± 2.5. Out of 11 studies, four reported CT findings were bilateral pleural effusion and multiple ground-glass pulmonary opacities with thickening interlobular septa. One study reported X-ray findings of diffuse infiltration. One study reported MRI findings as brain-sulcal loss, suggesting global oedema (Table ). The histopathological findings of individual studies are described in Tables and . The proportion of studies reporting autopsy findings in different organs was as follows: lung 81.8%, heart 54.5%, liver 54.5%, brain 36.4%, kidney 36.4%, spleen 27.3%, periodontal 18.2%, and bone marrow, colon, skin, muscles, salivary gland, adrenal gland, and vessels, 9.1% of each. The gross findings were reported in three studies, and histology was reported in 10, as shown in Tables and . The gross findings were pericardial and pleural effusion, hepatomegaly, splenomegaly, cardiomegaly, heavy soft lung, enlarged kidney, and enlarged brain. The pooled results of the autopsy findings of all 11 studies are summarised in Table . Table depicts immunohistochemistry and molecular markers in included studies. All studies reported positive SARS-CoV-2 by RT-PCR, and it was reported by IHC (immunohistochemistry) also in 85.7%. The CD68 was positive in 33.3% of cases by IHC. The electron microscopic findings were reported in 33.3%, showing SARS-CoV-2 as a spherical viral particle with spikes in different organs’ epithelium. The pooled results of laboratory findings of various studies are described in Table . Most studies showed that the D-dimers (8954.5 DDU) and fibrinogen (414.5 mg/dl) were significantly high. In most studies, laboratory tests were done before death. 

In the COVID-19 pandemic, there are some recommendations for autopsy performance. There should be at least a biosafety level-2 autopsy facility . In this pandemic, a complete autopsy (ideal) may not be possible because SARS-CoV-2 is highly contagious to autopsy staff; there are alternative autopsy methods like in situ sampling or minimally invasive techniques of puncture/core biopsy autopsies . This systematic review found that three studies partially performed the complete autopsy, and eight partially performed autopsies (Table ). Table shows the clinical parameters of included patients. The mean age of patients was 5.9 ± 5.7 years who got infected by COVID-19. The review had 15 (57.7%) girls and 11 (42.3%) boys, with a ratio of 1.36. The mean total duration of the disease (10 studies) was 12.6 ± 10.7 days and the mean duration of hospital stay (8 studies) was 7.8 ± 10.6 days. Children’s mean body mass index (three studies) was 3.8 ± 2.5. Out of 11 studies, four reported CT findings were bilateral pleural effusion and multiple ground-glass pulmonary opacities with thickening interlobular septa. One study reported X-ray findings of diffuse infiltration. One study reported MRI findings as brain-sulcal loss, suggesting global oedema (Table ). The histopathological findings of individual studies are described in Tables and . The proportion of studies reporting autopsy findings in different organs was as follows: lung 81.8%, heart 54.5%, liver 54.5%, brain 36.4%, kidney 36.4%, spleen 27.3%, periodontal 18.2%, and bone marrow, colon, skin, muscles, salivary gland, adrenal gland, and vessels, 9.1% of each. The gross findings were reported in three studies, and histology was reported in 10, as shown in Tables and . The gross findings were pericardial and pleural effusion, hepatomegaly, splenomegaly, cardiomegaly, heavy soft lung, enlarged kidney, and enlarged brain. The pooled results of the autopsy findings of all 11 studies are summarised in Table . Table depicts immunohistochemistry and molecular markers in included studies. All studies reported positive SARS-CoV-2 by RT-PCR, and it was reported by IHC (immunohistochemistry) also in 85.7%. The CD68 was positive in 33.3% of cases by IHC. The electron microscopic findings were reported in 33.3%, showing SARS-CoV-2 as a spherical viral particle with spikes in different organs’ epithelium. The pooled results of laboratory findings of various studies are described in Table . Most studies showed that the D-dimers (8954.5 DDU) and fibrinogen (414.5 mg/dl) were significantly high. In most studies, laboratory tests were done before death. 

The SARS-CoV-2 caused the COVID-19 pandemic that started in December 2019. COVID-19 has variable clinical presentations ranging from a mild symptomatic respiratory illness to fulminant ARDS (acute respiratory syndrome), multiorgan failure, and even death. The index study is one of the largest systematic reviews and meta-analysis of post-mortem findings in paediatric patients with SARS-CoV-2. In this review, we found that the lungs were mostly affected by COVID-19, which corroborated with several other studies [ , – ]. In lung pathology, DAD (diffuse alveolar damage) was found in 78.3% of paediatric autopsy cases, similar to adult lung autopsy findings . Histopathology findings of DAD due to COVID-19 were similar to other causes of DAD . CDC (centre for disease control) provided COVID-19 testing criteria (checklist positive) for detection of DAD . The fibrin thrombi were a consistent finding of COVID-19, and it was reported in almost all organs of paediatric autopsies in several studies [ , , , ]. Other findings like congestion, oedema, and haemorrhage in different organs were reported by various studies [ , , ]. After pooling the results, foci of band necrosis in the myocardium were found in 60% of cases, which concord with another study . In adult patients, myocardial necrosis was reported at 8%, significantly less than a paediatric autopsy . Acute tubular necrosis (ATN) of the kidney was found in 75% of cases which was correlated with findings of other studies . In the brain, the most common autopsy findings were oedema (87%) and reactive microglial (62%), which were similar to with Duarte-Neto et al., Ninan et al., and Kasereka et al. studies . In most of the studies of the adult autopsy, the brain showed foci of punctate haemorrhage, minimal inflammation and no myelin loss, no necrosis and microglial reaction . In autopsy series of 5 paediatric cases by Duarte-Neto et al., two children had the severe pre-existing disease (adrenal carcinoma and Edwards syndrome), and three patients had MIS-C (multisystemic inflammatory syndrome) with myocarditis, colitis, and meningoencephalitis . Similarly, Dolhnikoff et al. reported the cause of death as COVID-19-related MIS-C in their case . There was underlying disseminated TB in one case , and one was a post-liver transplant patient . The remaining cases were premorbid healthy, and death can be attributed to COVID-19 (Table ). It is difficult to attribute the death to COVID-19 if a patient has an underlying disease. The typical laboratory findings of COVID-19 in various studies were anaemia and thrombocytopenia . Most of the studies reported an elevated level of D-dimer (DDU) and fibrinogen (mg/dl) levels in COVID-19 patients in children . The similarities and differences between paediatric and adult autopsy findings are described in Table . There are some limitations of this review. Firstly, the number of patients is small as most studies are case reports. Secondly, it is challenging to attribute autopsy findings to COVID-19 in patients with underlying diseases. Finally, many studies only did a partial autopsy, not a complete one. 

The lung was the most commonly affected organ due to COVID-19. We suggest that autopsies are the best way to understand the pathophysiology of COVID-19 diseases and their correlation with clinical findings. To the best of our knowledge, this is one of the most extensive systematic reviews and meta-analysis of paediatric autopsy findings. 

The key points to assess the methodological quality of cross-sectional studies include inclusion criteria, methods to identify the condition, and clearly defined and reported outcome measures. 

