Evaluating the performance characteristics of five lateral flow assays for the detection of the SARS-CoV-2 nucleocapsid antigen.

In response to the COVID-19 pandemic, lateral flow assays (LFAs) for the detection of SARS-CoV-2 antigen have been proposed as a complementary option to the more costly and time consuming reverse-transcriptase polymerase chain reaction (RT-PCR). We assessed five commercially available SARS-CoV-2 antigen detecting LFAs (ASSUT EUROPE (Rome, Italy), Besthree (Taizhou, China), Encode (Zhuhai, China), Fortress (Antrim UK), and Hughes Medical (Buckinghamshire, UK), using samples collected from hospitalised individuals with COVID-19 and compared these results against established RT-PCR assays with the aim of estimating test performance characteristics. We performed a diagnostic accuracy study of the five LFAs on 110 inpatients with confirmed COVID-19 and 75 COVID-19 negative control participants. Assay evaluation was performed using a modified version of each manufacturer's protocol allowing for parallel testing of a single sample on multiple assays. Additional variables were studied including infection acquisition, oxygenation requirements at time of swabbing, and patient outcomes. The 110 patients were 48% (53) female, with mean age 67 years (range 26-100 years), and 77% (85) cases were community onset SARS-CoV-2. Across the five assays, sensitivity ranged from 64 (95% CI 53-73) to 76% (95% CI 65-85); Fortress performed best with sensitivity of 76% (95% CI 65-85). Specificity was high across all assays with 4/5 LFAs achieving 100%. LFA sensitivity was not dependant on RT-PCR cycle thresholds. SARS-CoV-2 antigen detecting LFAs may complement RT-PCR testing to facilitate early diagnosis and provide community testing strategies for identification of patients with COVID-19, however we find suboptimal test performance characteristics across a range of commercially available manufacturers, below WHO and MHRA pre-set sensitivity performance thresholds. With such variation in sensitivity between LFAs and PCR testing and between assay brands, we advise caution in the deployment of LFAs outside of environments with clinical oversight.

Point-of-care SARS-CoV-2 serological assays for enhanced case finding in a UK inpatient population.

Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) has become a global pandemic. Case identification is currently made by real-time polymerase chain reaction (PCR) during the acute phase and largely restricted to healthcare laboratories. Serological assays are emerging but independent validation is urgently required to assess their utility. We evaluated five different point-of-care (POC) SARS-CoV-2 antibody test kits against PCR, finding concordance across the assays (n = 15). We subsequently tested 200 patients using the OrientGene COVID-19 IgG/IgM Rapid Test Cassette and find a sensitivity of 74% in the early infection period (day 5-9 post symptom onset), with 100% sensitivity not seen until day 13, demonstrating inferiority to PCR testing in the infectious period. Negative rate was 96%, but in validating the serological tests uncovered potential false-negatives from PCR testing late-presenting cases. A positive predictive value (PPV) of 37% in the general population precludes any use for general screening. Where a case definition is applied however, the PPV is substantially improved (95.4%), supporting use of serology testing in carefully targeted, high-risk populations. Larger studies in specific patient cohorts, including those with mild infection are urgently required to inform on the applicability of POC serological assays to help control the spread of SARS-CoV-2 and improve case finding of patients that may experience late complications.

Bacterial and fungal coinfection among hospitalized patients with COVID-19: a retrospective cohort study in a UK secondary-care setting.

OBJECTIVES: To investigate the incidence of bacterial and fungal coinfection of hospitalized patients with confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in this retrospective observational study across two London hospitals during the first UK wave of coronavirus disease 2019 (COVID-19). METHODS: A retrospective case series of hospitalized patients with confirmed SARS-CoV-2 by PCR was analysed across two acute NHS hospitals (20 February-20 April 2020; each isolate reviewed independently in parallel). This was contrasted to a control group of influenza-positive patients admitted during the 2019-2020 flu season. Patient demographics, microbiology and clinical outcomes were analysed. RESULTS: A total of 836 patients with confirmed SARS-CoV-2 were included; 27 (3.2%) of 836 had early confirmed bacterial isolates identified (0-5 days after admission), rising to 51 (6.1%) of 836 throughout admission. Blood cultures, respiratory samples, pneumococcal or Legionella urinary antigens and respiratory viral PCR panels were obtained from 643 (77%), 110 (13%), 249 (30%), 246 (29%) and 250 (30%) COVID-19 patients, respectively. A positive blood culture was identified in 60 patients (7.1%), of which 39 were classified as contaminants. Bacteraemia resulting from respiratory infection was confirmed in two cases (one each community-acquired Klebsiella pneumoniae and ventilator-associated Enterobacter cloacae). Line-related bacteraemia was identified in six patients (three Candida, two Enterococcus spp. and one Pseudomonas aeruginosa). All other community-acquired bacteraemias (n = 16) were attributed to nonrespiratory infection. Zero concomitant pneumococcal, Legionella or influenza infection was detected. A low yield of positive respiratory cultures was identified; Staphylococcus aureus was the most common respiratory pathogen isolated in community-acquired coinfection (4/24; 16.7%), with pseudomonas and yeast identified in late-onset infection. Invasive fungal infections (n = 3) were attributed to line-related infections. Comparable rates of positive coinfection were identified in the control group of confirmed influenza infection; clinically relevant bacteraemias (2/141; 1.4%), respiratory cultures (10/38; 26.3%) and pneumococcal-positive antigens (1/19; 5.3%) were low. CONCLUSIONS: We found a low frequency of bacterial coinfection in early COVID-19 hospital presentation, and no evidence of concomitant fungal infection, at least in the early phase of COVID-19.

New-onset anosmia and ageusia in adult patients diagnosed with SARS-CoV-2 infection.

OBJECTIVES: We investigated the prevalence of anosmia and ageusia in adult patients with a laboratory-confirmed diagnosis of infection with severe acute respiratory distress syndrome coronavirus-2 (SARS-CoV-2). METHODS: This was a retrospective observational analysis of patients infected with SARS-CoV-2 admitted to hospital or managed in the community and their household contacts across a London population during the period March 1st to April 1st, 2020. Symptomatology and duration were extracted from routinely collected clinical data and follow-up telephone consultations. Descriptive statistics were used. RESULTS: Of 386 patients, 141 (92 community patients, 49 discharged inpatients) were included for analysis; 77/141 (55%) reported anosmia and ageusia, nine reported only ageusia and three only anosmia. The median onset of anosmia in relation to onset of SARS-CoV-2 disease (COVID-19) symptoms (as defined by the Public Health England case definition) was 4 days (interquartile range (IQR) 5). Median duration of anosmia was 8 days (IQR 16). Median duration of COVID-19 symptoms in community patients was 10 days (IQR 8) versus 18 days (IQR 13.5) in admitted patients. As of April 1, 45 patients had ongoing COVID-19 symptoms and/or anosmia; 107/141 (76%) patients had household contacts, and of 185 non-tested household contacts 79 (43%) had COVID-19 symptoms with 46/79 (58%) reporting anosmia. Six household contacts had anosmia only. CONCLUSIONS: Over half of the positive patients reported anosmia and ageusia, suggesting that these should be added to the case definition and used to guide self-isolation protocols. This adaptation may be integral to case findings in the absence of population-level testing. Until we have successful population-level vaccination coverage, these steps remain critical in the current and future waves of this pandemic.