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.

Overriding water table control on managed peatland greenhouse gas emissions

Global peatlands store more carbon than is naturally present in the atmosphere^1,2. However, many peatlands are under pressure from drainage-based agriculture, plantation development and fire, with the equivalent of around 3 per cent of all anthropogenic greenhouse gases emitted from drained peatland^3-5. Efforts to curb such emissions are intensifying through the conservation of undrained peatlands and re-wetting of drained systems⁶. Here we report eddy covariance data for carbon dioxide from 16 locations and static chamber measurements for methane from 41 locations in the UK and Ireland. We combine these with published data from sites across all major peatland biomes. We find that the mean annual effective water table depth (WTD_e; that is, the average depth of the aerated peat layer) overrides all other ecosystem- and management-related controls on greenhouse gas fluxes. We estimate that every 10 centimetres of reduction in WTD_e could reduce the net warming impact of CO₂ and CH₄ emissions (100-year global warming potentials) by the equivalent of at least 3 tonnes of CO₂ per hectare per year, until WTD_e is less than 30 centimetres. Raising water levels further would continue to have a net cooling effect until WTD_e is within 10 centimetres of the surface. Our results suggest that greenhouse gas emissions from peatlands drained for agriculture could be greatly reduced without necessarily halting their productive use. Halving WTD_e in all drained agricultural peatlands, for example, could reduce emissions by the equivalent of over 1 per cent of global anthropogenic emissions.

HIV/HCV/HBV testing in the emergency department: a feasibility and seroprevalence study

OBJECTIVES

The aims of this study were to to assess the feasibility of simultaneous testing for the blood-borne viruses (BBV), HIV, hepatitis C (HCV) and hepatitis B (HBV), in the Emergency Department (ED) and ascertain the seroprevalence for these three viruses in this setting.

METHODS

A pilot BBV testing program was undertaken as part of routine clinical care in the ED. All ED attendees aged between 16 and 65 years old who were able to consent were tested over a 55 week period on an opt out basis. Patients with positive test results were linked to clinical services. Interventions aimed at improving testing rates were implemented and evaluated by quality improvement (QI) methodology.

RESULTS

Of 25,520 age-eligible ED attendees, 6108 (24%) underwent BBV testing; an additional 1160 (4.5%) underwent a standalone HIV test (total of 7268 (28%) individuals).There were 83/7268 (1.1%) non-negative (ie reactive or equivocal) results for HIV and 103/6108 (1.7%) and 32/6108 (0.52%) for anti-HCV IgG and HBsAg, respectively. Of these, 12 (0.17%), 16 (0.26%) and 8 (0.13%) were new reactive tests for HIV, HCV and HBV, respectively, which were able to be confirmed on a second test. Specific QI interventions led to temporary increases in testing rates.

CONCLUSIONS

An opt out BBV testing program in the ED is feasible and effective at finding new cases. However, the testing rate was low at 24%. Although QI interventions led to some improvement in testing rates, further studies are required to identify ways to achieve sustained increases in testing in this setting.

Treatment-limiting renal tubulopathy in patients treated with tenofovir disoproxil fumarate

OBJECTIVES

Tenofovir disoproxil fumarate (TDF) is widely used in the treatment or prevention of HIV and hepatitis B infection. TDF may cause renal tubulopathy in a small proportion of recipients. We aimed to study the risk factors for developing severe renal tubulopathy.

METHODS

We conducted an observational cohort study with retrospective identification of cases of treatment-limiting tubulopathy during TDF exposure. We used multivariate Poisson regression analysis to identify risk factors for tubulopathy, and mixed effects models to analyse adjusted estimated glomerular filtration rate (eGFR) slopes.

RESULTS

Between October 2002 and June 2013, 60 (0.4%) of 15,983 patients who had received TDF developed tubulopathy after a median exposure of 44.1 (IQR 20.4, 64.4) months. Tubulopathy cases were predominantly male (92%), of white ethnicity (93%), and exposed to antiretroviral regimens that contained boosted protease inhibitors (PI, 90%). In multivariate analysis, age, ethnicity, CD4 cell count and use of didanosine or PI were significantly associated with tubulopathy. Tubulopathy cases experienced significantly greater eGFR decline while receiving TDF than the comparator group (-6.60 [-7.70, -5.50] vs. -0.34 [-0.43, -0.26] mL/min/1.73 m²/year, p < 0.0001).

CONCLUSIONS

Older age, white ethnicity, immunodeficiency and co-administration of ddI and PI were risk factors for tubulopathy in patients who received TDF-containing antiretroviral therapy. The presence of rapid eGFR decline identified TDF recipients at increased risk of tubulopathy.

Auditing HIV Testing Rates across Europe: Results from the HIDES 2 Study

European guidelines recommend the routine offer of an HIV test in patients with a number of AIDS-defining and non-AIDS conditions believed to share an association with HIV; so called indicator conditions (IC). Adherence with this guidance across Europe is not known. We audited HIV testing behaviour in patients accessing care for a number of ICs. Participating centres reviewed the case notes of either 100 patients or of all consecutive patients in one year, presenting for each of the following ICs: tuberculosis, non-Hodgkins lymphoma, anal and cervical cancer, hepatitis B and C and oesophageal candidiasis. Observed HIV-positive rates were applied by region and IC to estimate the number of HIV diagnoses potentially missed. Outcomes examined were: HIV test rate (% of total patients with IC), HIV test accepted (% of tests performed/% of tests offered) and new HIV diagnosis rate (%). There were 49 audits from 23 centres, representing 7037 patients. The median test rate across audits was 72% (IQR 32–97), lowest in Northern Europe (median 44%, IQR 22–68%) and highest in Eastern Europe (median 99%, IQR 86–100). Uptake of testing was close to 100% in all regions. The median HIV+ rate was 0.9% (IQR 0.0–4.9), with 29 audits (60.4%) having an HIV+ rate >0.1%. After adjustment, there were no differences between regions of Europe in the proportion with >0.1% testing positive (global p = 0.14). A total of 113 patients tested HIV+. Applying the observed rates of testing HIV+ within individual ICs and regions to all persons presenting with an IC suggested that 105 diagnoses were potentially missed. Testing rates in well-established HIV ICs remained low across Europe, despite high prevalence rates, reflecting missed opportunities for earlier HIV diagnosis and care. Significant numbers may have had an opportunity for HIV diagnosis if all persons included in IC audits had been tested.

Automatic oral fluid-based HIV testing in HIV screening programmes: automatic for the people

OBJECTIVES

UK guidelines recommend routine HIV testing in general clinical settings when the local HIV prevalence is > 0.2%. During pilot programmes evaluating the guidelines, we used laboratory-based testing of oral fluid from patients accepting tests. Samples (n = 3721) were tested manually using the Bio-Rad Genscreen Ultra HIV Ag-Ab test (Bio-Rad Laboratories Ltd, Hemel Hempstead, UK). This was a methodologically robust method, but handling of samples was labour intensive. We performed a validation study to ascertain whether automation of oral fluid HIV testing using the fourth-generation HIV test on the Abbott Architect (Abbott Diagnostics, Maidenhead, UK) platform was possible.

METHODS

Oral fluid was collected from 143 patients (56 known HIV-positive volunteers and 87 others having contemporaneous HIV serological tests) using the Oracol+ device (Malvern Medicals, Worcester, UK). Samples were tested concurrently: manually using the Genscreen Ultra test and automatically on the Abbott Architect.

RESULTS

For oral fluid, the level of agreement of results between the platforms was 100%. All results agreed with HIV serology. The use of the Oracol+ device produced high-quality samples. Subsequent field use of the test has shown a specificity of 99.97% after nearly 3000 tests.

CONCLUSIONS

Laboratory-based HIV testing of oral fluid requires less training of local staff, with fewer demands on clinical time and space than near-patient testing. It is acceptable to patients. The validation exercise and subsequent clinical experience support automation, with test performance preserved. Automation reduces laboratory workload and speeds up the release of results. Automated oral fluid testing is thus a viable option for large-scale HIV screening programmes.

Routine HIV testing in the emergency department: tough lessons in sustainability

OBJECTIVES

Routine HIV testing in nonspecialist settings has been shown to be acceptable to patients and staff in pilot studies. The question of how to embed routine HIV testing, and make it sustainable, remains to be answered.

METHODS

We established a service of routine HIV testing in an emergency department (ED) in London, delivered by ED staff as part of routine clinical care. All patients aged 16 to 65 years were offered an HIV test (latterly the upper age limit was removed). Meetings were held weekly and two outcome measures examined: test offer rate (coverage) and test uptake. Sustainability methodology (process mapping; plan-do-study-act (PDSA) cycles) was applied to maximize these outcome measures.

RESULTS

Over 30 months, 44,582 eligible patients attended the ED. The mean proportion offered an HIV test was 14%, varying from 6% to 54% per month over the testing period. The mean proportion accepting a test was 63% (range 33-100%). A total of 4327 HIV tests have been performed. Thirteen patients have been diagnosed with HIV infection (0.30%). PDSA cycles having the most positive and sustained effects on the outcome measures include the expansion to offer blood-based HIV tests in addition to the original oral fluid tests, and the engagement of ED nursing staff in the programme.

CONCLUSIONS

HIV testing can be delivered in the ED, but constant innovation and attention have been required to maintain it over 30 months. Patient uptake remains high, suggesting acceptability, but time will be required before true embedding in routine clinical practice is achieved.

Comparison of two cohorts of patients presenting with AIDS: patients with previously known HIV diagnoses and true late presenters

OBJECTIVES

We aimed to identify the factors associated with developing AIDS 6 months or more after an HIV diagnosis, and to examine how post-HIV diagnosis AIDS (PHDA) patients differed from true late presenters (HIV diagnosed concurrent with the first AIDS presenting event) in their demographics and comorbidities.

METHODS

A retrospective analysis was undertaken of all inpatients admitted to a large HIV unit presenting with the following AIDS-defining infections: cryptococcal meningitis, cerebral toxoplasmosis or Pneumocystis jirovecii pneumonia between 1 January 2005 and 31 December 2010.

RESULTS

114 HIV-positive patients presented with AIDS-defining infections. Compared with late presenters, PHDA patients had a larger proportion of migrants and visitors (53.7% vs. 34.0%, p=0.047), were more likely to inject drugs (9.3% vs 0.0%, p=0.032), had more previous HIV-associated diseases (57.4% vs. 12.8%, p=0.000), psychiatric comorbidities (35.2% vs. 12.8%, p=0.009), rates of alcohol abuse (24.1% vs. 4.3%, p=0.005) and reported social issues (25.9% vs. 0.00%, p=0.000). 88.9% of PHDA patients were lost to follow-up for a period of at least 4 months since diagnosis. Common reasons for clinic non-attendance included travel, social issues, transfer of care and treatment avoidance. Common reasons for antiretroviral treatment breaks included drug side effects, negative beliefs about medication, incompatible lifestyles and social issues.

CONCLUSIONS

Compared with late presenters, PHDA patients demonstrate clear demographical differences including higher rates of psychiatric comorbidities, social issues, alcohol and substance abuse. Many PHDA patients default follow-up. The retention of HIV patients in care and on treatment must be addressed by clinicians to prevent avoidable morbidity.

Power Doppler 'blanching' after the application of transducer pressure

The aim of this study was to determine if transducer pressure modifies power Doppler assessments of rheumatoid arthritis synovium at the metacarpophalangeal joints and metatarsophalangeal joints. Five rheumatoid arthritis patients of varying degrees of 'disease activity' and damage were assessed with power Doppler ultrasound scanning of the dominant hand second to fifth metacarpophalangeal joints. Two rheumatoid arthritis patients had their dominant foot first to fifth metatarsophalangeal joints assessed with power Doppler ultrasound. Ultrasonography was performed with a high frequency transducer (14 MHz) with a colour mode frequency of 10 Mhz, and a standard colour box and gain. In the joint that showed the highest power Doppler signal, an image was made. A further image was taken after transducer pressure was applied. In all patients, there was increased flow to at least one joint. After pressure was applied, power Doppler signal intensity markedly reduced in all images and in some there was no recordable power Doppler signal. Increased transducer pressure can result in a marked reduction or obliteration in power Doppler signal. This power Doppler 'blanching' shows the need for further studies to evaluate sources of error and standardization before power Doppler ultrasound becomes a routine measure of 'disease activity' in rheumatoid arthritis.